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View Full Version : Good Ol' 3800!


99LeCouch
02-26-2009, 10:13 PM
Managed to squeeze 31 mpg and 514 miles out of 16.6 gallons of fuel in my 1999 Buick LeSabre, with the 3.8l 3800 Series II V6. For this it got a tuneup. :bananajump:

Most of this was highway doing about 60, yet 20% was purely in-town, stoplight-to-stoplight driving.

What a great highway engine. Too bad GM killed it in favor of more complex, less-efficient designs. Sometimes you really can't improve upon a classic.

kingcommute
02-27-2009, 10:04 AM
+1 on the 3800. A much better powerplant than those that replaced it. We had a 98 Intrigue that was a marvel on the highway. Didn't know about hypermiling back then, so our town mileage would always pull our averages way down, but on long trips it would shine.

jkp1187
02-27-2009, 11:06 AM
Totally. The old 3800 in my Impala is equaling the allegedly more fuel-efficient 3.5L in my wife's G6. The powerplant is bulletproof, and they should've kept it going.

kingcommute
02-27-2009, 11:24 AM
and the Impala is a much smaller car - so not only is it kicking the 3.5L's ass from a displacement vs. displacement standpoint it is doing so with more mass to move around. and they killed it because supposedly consumers wanted more high-feature motors. Are there any GM products these days that still utilize that motor or its successor the 3.9?

jkp1187
02-27-2009, 11:37 AM
Didn't realize the 3.9L was the successor. I think the "base" level latest-generation Impala uses 3.9... And maybe the G6 GTP. But the latter is supposed to be tuned for sport, so the MPG probably won't be as good.

kingcommute
02-27-2009, 11:57 AM
Looks like you can still get the 3.9 in the Buick LaCrosse, Lucerne, and Chevy Impala

The 08 grand Prix uses it too in the base model and as you said the GXP version of the G6. The 3.6 Direct Injection has replaced it in most other applications it would seem.

From what I've read on the 3.9 - they did a good job updating the 3800 - increased the power some, but didn't decrease the FE any.

I blame Car and Driver - they were always taking pot-shots at the 3800. I think those auto-mags have some influence on the direction that manufacturers head. Do I have proof of this, no - its just my own personal theory.

jkp1187
02-27-2009, 12:38 PM
The chattering classes were always complaining about the lack of "refinement" in the old pushrod 3800.

I don't see it. Compared to what? The 3800 feels smooth as can be in regular highway cruising, and whenever you need it to accelerate, there is sufficient power to get moving as fast as anyone would want to sanely drive. Again, relatively smooth delivery, too. (And if that wasn't enough, there was a supercharged application.)

The 3.5L frankly sounds thrashy under load - almost like a 4 cyl. It doesn't like higher RPMs. It's nice to have the tiptronic-style shifter, true, but if you stay in 3rd gear and aren't totally gunning it, power gets inexplicably cut at a certain point. It must be the torque converter locking up, but it often happens at just the wrong moment (e.g., I'm trying to gain some speed prior to going up a hill.) I really have to pay attention to the tachometer to see the Impala's torque converter lock.

The 3.5L is not awful, but as to whether or not it's an improvement...well, let's just say I'm skeptical.

Oh -- and BTW, according to Edmunds, the '00 Impala LS and the '06 G6 GT are about the same curb weight. Impala is maybe ~40lbs. heavier. I was really surprised at that....they made a SMALLER car that weighed the same??!?

jkp1187
02-27-2009, 12:50 PM
From what I've read on the 3.9 - they did a good job updating the 3800 - increased the power some, but didn't decrease the FE any.


The fact that they're STILL using it (despite the flack from the automotive press,) says a lot about its quality and utility. It's a workhorse powerplant.

Taliesin
02-27-2009, 01:35 PM
The old Chevy 350 (5.7L?) from the early to mid 70's was another workhorse. I have had quite a few and getting 25+ out of a mid-size car (at that time, now it would be a large car weighing almost as much as a SUV) with a V8 engine was easy to do (don't ask, I was young and dumb at the time). Somehow they moved away from that and now their mid-size cars can't get that much.

They attempted to downsize it to a 5.0L, but that was a waste. Less power, less reliable, and worse FE.

phoebeisis
02-27-2009, 04:52 PM
GMs pushrod V-8s get pretty good mpg when driven with FE in mind.
My 1998 Suburban-5.7- 208,400 miles-gets 21.3 mpg on very long highway trips with the AC blasting to cool 150 cubic feet of cargo area. Granted 21 mpg isn't great, but considering it is carrying 3-4 passengers and maybe 800+ of other cargo, and the age and miles it is pretty good.
I set the cc to 68 mph and otherwise stay under the speed limit, but not waaaaay under the limit.
The more modern 5.3 Suburbans are at least 3 highway mpg better because of the motor,and slightly more aero shape.
Driven 63 mph they(Suburbans-Tahoes) should be good for 25 mpg highway-about 5 mpg down on a minivan.They(2007 on) should approach 20 mpg city with motor on P&G and shutting down at redlights.
They are pretty useful if you carry lots of people,animals,things. Not so useful if you drive alone most of the time.They are about 1500 lbs heavier than a midsized car, and a good 10-15 mpg down vs the car, so they are expensive to operate as a primary car(better to buy a cheap used one as backup/second car etc).
Luck,
Charlie
The 3800 is a 3/4 varient of the SBCs more or less-tried and true. My 5.7 is very, very smooth and quiet.

MaxxMPG
02-27-2009, 05:28 PM
The 3800 and 3900 are two different engines, although the 3900 replaced the 3800 in applications where the 3500 didn't quite meet the need.

The 3800 is a 90 degree V6 and is the same old Buick 231 V6 that began life in 1962 as an iron version of the aluminum 215V8 with the back two cylinders lopped off. The stronger iron meant less metal was needed between the cylinders so they were able to increase the bore and get 225 cubic inches out of it. When it was resurrected in the 1970s to help meet CAFE they added a bit to the stroke and arrived at 3.8 liters.

The 3900 is a 60 degree V6 and is a larger displacement version of the 3500, which itself is an evolution of the 2.8 liter V6 that rolled out in 1979 for the first time in the ill-fated X cars (Citation, etc). Because the block is so small and the bank angle so narrow, the 3900 is actually an "offset bore" design, where the centerline of cylinder bores do not intersect with the centerline of the crankshaft. The cylinders themselves were moved "outward" to make room for the larger cylinder bores.

The 3800 is a Buick design which means it makes all the power at low revs. Wind it to the redline and it will moan and grumble and not make much more power. The auto mags love to bash that characteristic because it doesn't meet their vision of "sporty". But low end torque means the tach never needs to go above "2" in any normal driving.

The 3500 is a Chevy design and is also a pushrod-style "all torque at low revs" powerplant. It will also buzz and grind if you push it to 6000, but that is not surprising considering the pushrod design and somewhat long piston stroke.

Considering that the 3800 is 17 years older than the 3500/3900, the added fine tuning over the years made it a perfect "Buick" engine - silent at idle and with ample power for people who don't usually press their accelerator more than 1/4 inch. The 3900 is not a bad engine, but it will never reach the FE capabilities of the 3800. Even the newer 3600 HF V6 engine can't match the old iron 3800. Progress, indeed.

ILAveo
02-27-2009, 08:40 PM
The chattering classes were always complaining about the lack of "refinement" in the old pushrod 3800.
....


Many times "lack of refinement" is what people say about somebody else's car when they can't quite figure out why theirs cost more. I've noticed that BMW owners often use that phrase.;)

99LeCouch
02-28-2009, 01:16 AM
Lack of refinement? Excuse me? My engine is nearly vibration-free despite having old, worn (stiffer) mounts and subframe bushings. I can barely feel the vibration through the steering wheel when the car is on. And cannot hear it at highway speeds except when going uphill. Plus it never feels strained to deliver its power when called upon. 5700 RPM does not sound or feel strained during the bi-annual Italian tuneup. It just has the most unique and lovely sound I've ever heard out of an engine.

For an old fogey car this one gets around quite efficiently now that the nut between the wheel and seat has been adjusted. I love having gobs of torque available low in the rev range. Makes my in-town FE better. And don't have to use full throttle to do the exceedingly rare pass!

Now on to 600+ miles per tank!

jkp1187
02-28-2009, 09:30 AM
I have to agree -- my 3800 sounds just great at the upper end of its rev-range. The 3.5L sounds like it's straining.

ALS
02-28-2009, 09:38 AM
My mom has one in her 99 Park Ave (12,800 miles). That engine is sweet and when pushed runs like a bear. One of these days I'll have take her out on I-75 in SW Florida and see what she can do in the MPG department.

99LeCouch
02-28-2009, 02:22 PM
31-33 with minimal techniques, 36 if you have a ScanGauge and keep between 60 and 65. Maybe 37 if you can go a whole tank on flat ground.

The PA is a stretched LeSabre.

scramblejim
02-28-2009, 02:58 PM
The Impala is a bigger car than the G6. The Impala, Grand Prix, Century, Intrigue are all W platform cars. The Impala and newer Grand Prix use an aluminum subframe. The G6, 2004 and newer Malibu, Aura, are all Z platform cars. The H body cars are the LeSabre and Bonneville, and now the Lucerne. The C body car was the Park Ave.

98CRV
02-28-2009, 07:40 PM
Managed to squeeze 31 mpg and 514 miles out of 16.6 gallons of fuel in my 1999 Buick LeSabre, with the 3.8l 3800 Series II V6. For this it got a tuneup. :bananajump:

Most of this was highway doing about 60, yet 20% was purely in-town, stoplight-to-stoplight driving.

What a great highway engine. Too bad GM killed it in favor of more complex, less-efficient designs. Sometimes you really can't improve upon a classic.

Nice job! Is that your best tank?

99LeCouch
02-28-2009, 09:23 PM
It's my longest tank yet. I've come close to 500 miles a bunch of times. This time I got it!

Have gotten better mileage on shorter distances, but that could have been skewed since the pumps weren't the same.

98CRV
03-01-2009, 11:51 AM
It's my longest tank yet. I've come close to 500 miles a bunch of times. This time I got it!

Have gotten better mileage on shorter distances, but that could have been skewed since the pumps weren't the same.

Well that is just plain grand!:Banane02:

Good work!

phoebeisis
03-01-2009, 01:47 PM
The old V-pushrod motors have one really significant advantage over the V-OHC motors-they can be narrower which makes it easier to pack them into that crowded engine bay. This is probably the only true advantage they have, but it is important.


Charlie

99LeCouch
03-01-2009, 01:58 PM
Crowded engine bay? A GM H-Body? This car is one of the easiest-access cars I've worked on. Pretty much everything is where you can get at it, even the rear-bank plugs. Clamber onto the front bumper, lean over the engine, and they're right there.

Other 3800-powered cars such as the W-bodies are slightly worse, but still not bad.

A DOHC V6 I'd hate to replace plugs on.

MaxxMPG
03-01-2009, 02:07 PM
The old V-pushrod motors have one really significant advantage over the V-OHC motors-they can be narrower which makes it easier to pack them into that crowded engine bay. This is probably the only true advantage they have, but it is important.
Charlie

Generally speaking, the overhead cam engines have better airflow through the ports and so can make more power at higher rpm. Since horsepower is just "torque over time", adding 20% to the redline speed adds 20% to the net horsepower if the torque output were to be perfectly flat. Moving the torque curve higher in the rev band means a higher horsepower number, which sells cars and charms the auto mags, but without VVT, the little DOHC rev motors will feel weak and flat at lower rpm.

The pushrod engines have less internal friction, are smaller in size, far less complicated, far more tolerant of neglect, and lighter in weight (when built from the same materials). But they are limited in the rev band because of the greater valve train inertia (pushrods and rocker arms changing direction 50 times a second at 6000rpm), and their intake and exhaust ports don't "flow" as well. For anyone whose tach never sees the high side of "3", there is simply no difference in driveability or noise. At low revs, the pushrod engine has a theoretical advantage in efficiency, due to less friction and fewer moving parts, but the difference is not great enough to demand the OHV powerplant.

Those of us who give a darn about reducing our petroleum usage can get along quite well with our "crude" "archaic" "buzzy at the redline" "old school" "stuck in the '70s" "unrefined" OHV engines. In my own auto ownership experience, I've seen better real world FE from my OHV engines (consistently over 30mpg with 3.1L and 3.5L V6s in five different cars) than OHC engines (Saturn 3.0L DOHC that struggled to reach 30mpg, just over 30mpg with lots of easy driving with a Mitsu 3.0L SOHC).

phoebeisis
03-01-2009, 04:04 PM
99LECOUCH,

Yep, that is why it has such a nice engine bay-it is missing that extra 2-3" of height on top of the head.

MAXXMPG Yes, in general the OHC can rev a bit higher, and they can make more power per cubic inch because of this better high rpm valve control.
However, as you say/imply- and judging from the relative EPA FE of the 5.3 GM vs the 5.7 and 5.6 Toyota and Nissan 4 valve motors- IN REAL WORLD driving the 4 valve OHC motors don't seem to have any real world advantage as people and "stuff' mover over GMs old tech pushrod 2 valve motors.

Chevy/GM somehow has made the 5.3 perform as well-- real world- as Toyota's 4 valve 5.7 and Nissan's 4 valve 5.6.
On the same 3000 mile trip
Suburban 5.7 21.3 mpg 68 mph cc on 6000 lbs loaded
Titan 5.6 V-8 19.9 mpg 66 mph cc on 5700 lbs loaded
Tundra 4.7 V-8 15.9 MPG at 73 mph cc on 5500 lbs loaded
Tacoma 2.4 4 cyl AT 24 MPG at 75 mph cc on 3500 lbs loaded
Honda Pilot AWD V-6 22.3 MPG at 73 mph CC on 5200 lbs loaded
Driven the same way the Pilot would have been 3 mpg better, and the Tacoma would have been about 5 mpg better, the Tundra would have been about 3 mpg less.

The good mpg of the Suburban isn't because of tall gearing- it turns 1750 rpms at 60 mph, more than the Titan(1550) Pilot (1650), but less than the Tundra(2000).

The small 235/75 15" wheels/tires are certainly a plus,I think.

The current 5.3 is a full 3 mpg better than the old 5.7.They are 25mpg highway vehicles at 64 mph.Basjoosed-they might approach 30 mpg(granted they would be 3 or sofeet longer!)

Charlie

jkp1187
03-01-2009, 05:19 PM
Crowded engine bay? A GM H-Body? This car is one of the easiest-access cars I've worked on. Pretty much everything is where you can get at it, even the rear-bank plugs. Clamber onto the front bumper, lean over the engine, and they're right there.

Other 3800-powered cars such as the W-bodies are slightly worse, but still not bad.

A DOHC V6 I'd hate to replace plugs on.


Hmmm.... It's a pain to reach the plugs in the back bank of the Impala's 3800. And did you ever try to check the power steering fluid? The manual says the reservoir is at the back of the engine....but do you see it there anywhere? (I found it.....but it is in one of the most ridiculous locations imaginable.)

Not that an OHC V-6 engine would be better, of course. Far from it.

99LeCouch
03-01-2009, 08:16 PM
It's not too bad on mine once the strut bar gets taken off. Which takes all of 1 minute. I've changed the power steering fluid several times, so I know all about access back there.

W-bodies have the front dogbone mounts and generally smaller engine bays because they're meant as "sportier" cars, while H-bodies are cushy tanks meant for highway cruising. I do know that engine work on this car is pretty easy since there's space to swing a wrench.

I took a look at the engine bay of an older Toyota pickup today when jump-starting it. Eek! It was cramped.

kvsdude
03-31-2009, 01:24 PM
An amazing engine.
I had a '99 Pontiac Grand Prix before giving it away to my 17 year old bro when I bought my new Mazda3. It's got 100k on it and feels like when it had 50. I just felt like getting a new car, nothing wrong with the ponti.

I took a trip from NJ to VA and got 29MPG with vent shades and going around 80mph.

The overdrive on those engines are crazy. I would try to glide in neutral to save gas and it actually felt exactly the same! That doesn't happen in my Mazda, which is only more fuel efficient due to being a 4cyl compact.

My dad's got an '03 Bonnie. It's a crappy car in that everthing is falling apart - except for his 3800 engine and trans.

Nevyn
03-31-2009, 03:58 PM
It's not too bad on mine once the strut bar gets taken off. Which takes all of 1 minute. I've changed the power steering fluid several times, so I know all about access back there.

W-bodies have the front dogbone mounts and generally smaller engine bays because they're meant as "sportier" cars, while H-bodies are cushy tanks meant for highway cruising. I do know that engine work on this car is pretty easy since there's space to swing a wrench.

I took a look at the engine bay of an older Toyota pickup today when jump-starting it. Eek! It was cramped.

I have one of those. To do the rear ANYTHINGS you have to jack the whole front end off the ground, disconnect the battery, put the car in neutral, take off the motor mounts, then ROTATE THE ENGINE BLOCK to get at the backside.

*mutters* and then if something goes wrong you have to do it all over again......:mad::cry:

99LeCouch
04-01-2009, 12:00 AM
Yeah, I've heard horror stories of plugs on Grand Prix's. Great highway cars also, but darned if I would want to work on one.

Nevyn
04-01-2009, 09:57 AM
Our GP has the 3100, but my father-in-law has a 3800. I'll have to take a gander at his engine bay sometime and see if it's as tight as mine. What transmission do you have to go with it? the 4T60 or the 4T65? I love the way they'll let the car just loaf down the highway doing 50 mph at 1500 RPM.

kingcommute
04-01-2009, 11:07 AM
The bay on our now-traded Olds Intrigue was fine except for the rear bank of plugs - everything was done blind when we changed them. Nothing is as bad as a Mazda Mpv though.....2/3 of the motor is underneath the overhang in the engine bay. Terrible.

I still wish we had that Olds though - twas a dang good car and much better than what we traded it for. Comfortable on long trips, well-appointed, and plenty of power if it was ever needed.

jkp1187
04-05-2009, 05:40 PM
Annoyingly, I just got a Blackstone oil analysis report from the latest oil change... It turns out that small amounts of coolant were found in the oil. Not a big problem yet - but could this be the lower intake manifold leak that people have reported on the 3800?

Pryme
04-05-2009, 07:01 PM
Annoyingly, I just got a Blackstone oil analysis report from the latest oil change... It turns out that small amounts of coolant were found in the oil. Not a big problem yet - but could this be the lower intake manifold leak that people have reported on the 3800?

Or possibly head gasket. :mad:

MaxxMPG
04-05-2009, 07:37 PM
The 3800s have been known to have a porous engine block that allows coolant and oil to wick through the metal. If that is the case, it never gets any better or any worse, and could potentially have existed since the car was new. If subsequent testing reveals more coolant in the oil, then the manifold gasket is the likely suspect. The new gaskets they use are supposedly the surefire fix for the problem.

99LeCouch
04-06-2009, 08:44 AM
Coolant in oil is more a sign of lower IM gaskets than a failed head gasket.

Or what Maxx said.

jkp1187
04-06-2009, 12:18 PM
I asked the woman from Blackstone (they called me up when the analysis was complete to talk over the results - a nice touch, I thought,) and she thought it unlikely that it was the head gasket, as she did not see certain metals present in the oil that would indicate head gasket failure.

The 3800s have been known to have a porous engine block that allows coolant and oil to wick through the metal. If that is the case, it never gets any better or any worse, and could potentially have existed since the car was new. If subsequent testing reveals more coolant in the oil, then the manifold gasket is the likely suspect. The new gaskets they use are supposedly the surefire fix for the problem.


Interesting - I did not know that. In any event, (and per Blackstone's recommendation,) I will keep oil changes to 3,000 miles at most, and monitor the situation.

It was good to see that, other than this small leak, there were absolutely nothing else wrong with the engine.

How much do you think I should pay an independent shop to have the LIM replaced, if it comes to that?

MaxxMPG
04-06-2009, 03:04 PM
I don't know anyone who has had the lower intake gaskets replaced, so I don't know the exact cost, but a quick search online shows a cost averaging $350 for an independent shop and $650 at a dealer. Repair costs vary by location, so calling around should give a good idea of cost for you. The problem is in the gasket material's incompatibility with DexCool and not a flaw in the engine design, so the new gasket cures the problem.

Check the oil every few hundred miles or so, and if it starts to look "foggy", it has coolant mixed in and an oil change is recommended. If the issue is a porous block, the next oil change analysis will reveal roughly the same coolant contamination.

99LeCouch
04-06-2009, 04:04 PM
There are also a lot of "gearheads" within a few hour's drive of you who would help you do the repair a lot cheaper than a shop would.

phoebeisis
04-06-2009, 04:54 PM
GM V-8s 5.7 and 5.3 -also I known for the intake manifold gasket failure. I have no idea why this failure is kinda common. I've heard 'stories" that it is due to the Dexcool coolant, but I doubt that.
Charlie

99LeCouch
04-06-2009, 10:42 PM
Dex-Cool plus the type of nylon used in OEM gaskets equals failure. I'm replacing the gaskets with the aluminum ones this summer. Also doing the OEM upper intake with a re-designed unit while everything's apart.

jkp1187
04-07-2009, 11:47 AM
On the subject, found this write-up on how to do the LIM gasket replacement:

http://www.naioa.com/v2/modules.php?name=Articles&pa=showarticle&pid=16

(May require joining the forum to see.)

jkp1187
04-14-2009, 09:45 AM
Not so good ol' 3800:

http://www.detnews.com/article/20090414/AUTO01/904140392/1148/rss25


Tuesday, April 14, 2009
GM recalling 1.5M vehicles over potential fires
Associated Press

Washington -- General Motors Corp. is recalling 1.5 million vehicles because of potential engine fires.

GM says there have been no reports of any fires or injuries.

Some of the recalled vehicles are no longer in production. The recall includes the 1998-1999 Oldsmobile Intrigue, the 1997-2003 Pontiac Grand Prix, 1997-2003 Buick Regal, and the 1998-2003 Chevrolet Lumina, Monte Carlo and Impala.

It involves vehicles with a 3.8-liter V6 engine. The government says drops of oil could fall into the exhaust system and cause a fire in the engine.

GM spokesman Kerry Christopher says it was a precautionary measure for consumers.

timtona
05-05-2009, 11:57 AM
hello everyone im new here. i have a 90 olds toronado with the 3800, it runs great but is only getting 13.6 mpg any ideas? its got fresh fluids and a tune up.it should really be doing better than that i think

MaxxMPG
05-05-2009, 12:05 PM
hello everyone im new here. i have a 90 olds toronado with the 3800, it runs great but is only getting 13.6 mpg any ideas? its got fresh fluids and a tune up.it should really be doing better than that i think

Welcome to CleanMPG!

First step - Read http://www.cleanmpg.com/forums/showthread.php?t=1510

The '90 Toronado is a heavy car, and all the comments and advice you read in this thread apply to your car. Keep it rolling. Easy on the accelerator and coax it to top gear and keep it there. Keep the engine rpm under 2000 on acceleration and under 1500 on the highway.

For car setup - consider setting tire pressure closer to the number shown on the sidewall. Check that there are no stuck calipers or worn wheel bearings that are causing drag. Check tire tread for odd wear that could suggest misalignment. Your car should feel like it's freewheeling when coasting. If it feels like it's being dragged down, as if downshifted, look for the cause of the drag.

Your car is not OBD-II compliant so a ScanGage won't work. But I had a '90 Olds Cutlass Int'l that had both average and instant FE in the trip computer. Your Toro may have the same. If it does, use it as a guide.

And ask questions here. We're happy to help!

timtona
05-05-2009, 03:47 PM
i have all the tires at 37psi, there are no stuck calipers, although i do need an alignment. since it does only have a 1 wire oxygen sensor could i run a rheostat on it to adjust my air fuel ratio?

PaleMelanesian
05-05-2009, 03:59 PM
13.6 mpg means there is something WRONG with the car. Don't try anything "special" until you get it fixed. I'd recommend against messing with the o2 sensor at all. Many pitfalls and little to gain, especially with a poorly running engine.

MaxxMPG
05-05-2009, 04:08 PM
i have all the tires at 37psi, there are no stuck calipers, although i do need an alignment. since it does only have a 1 wire oxygen sensor could i run a rheostat on it to adjust my air fuel ratio?

Your '90 Toro is rated at 16 city / 24 highway / 19 combined under the '08 EPA. Old ratings were 18/21/27. Your stated MPG is about right if you are driving mostly around town, although there is much room for improvement.

Where are you located and what does your daily commute entail?

I would recommend against fiddling with the O2 sensor, as changing the value won't do much more than switch the CEL on. The O2 sensor should be changed if a diagnostic test shows that it is getting lazy (long swings between rich/lean). Also, your automatic trans is the old 440T4, and it uses a throttle cable to control shift points. Be sure this throttle cable is properly adjusted so that upshifts happen promptly. A very slight misadjustment of that cable can cause delayed upshifts and lower fuel economy.

Be sure you aren't carrying extra cargo in the car, keep upshifts at or below 2000rpm by using a gentle foot on the throttle, and keep the car rolling whenever possible. Your car should shift to 4th gear at or above 45mph. Consider planning routes that will take you on roads with few lights or other stops and where this speed is legal and practical.

My '90 Olds Cutlass had the same transmission, but the Chevy 3.1 engine. A bit lighter and about the same aero drag. And I was able to get 44mpg on the instant FE at 44mph - the lowest speed it would hold onto 4th gear. So there is certainly room for better FE in the car and its powertrain.

timtona
05-05-2009, 05:14 PM
thats exactly what i dont understand... it runs great,idles great. but once ina while, while starting it will backfire then miss for a couple cycles untill it straightens out. could i have a bad injector?

timtona
05-05-2009, 05:20 PM
i have removed over 300 pounds of accessories, sound deadener, a/c,air ride,spare tire and jack. etc. it also has a cold air intake, free flowing exhaust and oversize plug wires so i think my stats should definately be higher than stock. most of my driving is city, stop- and go though. would a bad iat sensor give me bad mileage? mine looks a little corroded

MaxxMPG
05-05-2009, 06:03 PM
i have removed over 300 pounds of accessories, sound deadener, a/c,air ride,spare tire and jack. etc. it also has a cold air intake, free flowing exhaust and oversize plug wires so i think my stats should definately be higher than stock. most of my driving is city, stop- and go though. would a bad iat sensor give me bad mileage? mine looks a little corroded

The cold air intake and custom exhaust system are designed and intended for more power, which is the opposite of increased fuel efficiency. Both lead to denser air and more airflow through the engine, and then engine will add a pound of gas for every 14.7 pounds of cold air it can pump through. The IAT sensor, if it's bad enough, can cause a problem with air/fuel ratio calculation.

Remember that auto manufacturers don't add any extra parts to the engine management as doing so adds cost to manufacturing and also repair or warranty work. So everything included as stock on the car is necessary if you want to reach or exceed the EPA estimates, and the computer that controls spark and fuel is programmed to work in concert with the stock parts. Depending on what is replaced or enhanced, fuel economy will almost certainly suffer to some degree, and worn or defective parts will compound the condition. You can mitigate the loss by using hypermiling techniques, but the tank averages won't really impress until the car is running as the manufacturer intended.

The cough on startup could be a worn timing chain that skipped a tooth. How many miles are on the engine?

If you read the posts from 99LeCouch, he's getting "teens around town". It's tough to get much more out of an almost-two-ton car with a pushrod V6 and slushy automatic with the extreme low first gear. But read the "Beating the EPA" article and look up the terms DWB and DWL by clicking on the question mark next to each. For those of us with big GM V6 engines, these two techniques are our closest friends.

timtona
04-11-2011, 12:24 AM
hey all i havent been here in a while but heres a follow up on my mpg issues, i was getting 13.6 back in 2009 first i found my ignition module was going bad, so i upgraded to delco type 2 module and coil packs gas mileage went to 14.7,then found an open plug wire,15.3,cleaned the map sensor with rubbing alcohol and a q-tip.,16.4, indexed the spark plugs, 16.6, finally replaced the stretched timing chain, added new gears and tensioner and disabled cam driven the balance shaft by taking the gear off. currently getting 20.4 city, if anyone has an older 3800 with over 100,000 miles i suggest changing the timing gears, chain and tensioner, at 145,000 mine was so badly stretched it barely sat on the gears and the plastic tensioner was worn down to the metal backing plate. for the old 3800 who says you cant teach an old dog new tricks?

Right Lane Cruiser
04-11-2011, 09:36 AM
Nice work!!! :thumbs_up:

FSUspectra
04-11-2011, 10:03 AM
Well it sounds like you're bringing that old dog back into shape! ;)

Phantom
05-11-2011, 02:24 PM
I love the 3800 I have owned several over the years with both tall and short gearing on both the Series I and Series II, even have used the upper intake from the Series III.

Coolant in the to be taken care of now keep an eye on the coolant level to make sure it is not dropping. Replacing the gasket is not hard it just takes some time look at http://pontiacbonnevilleclub.com/forum/index.php for a walkthrough.

Changing the back spark plugs on the 3800 can be difficult but is easier on the GrandPrix if the front dogbone motor mount bolts are removed and a tiedown is used on the bracket to the fraim there are a few holes the hook can be placed. Now slowly bring the engine forward by clicking the straps tighter, hook the straps on before removing the bolts (there is only one on each side). That will give you a few extra inches to get to it.



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