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The Terrible 3.4L DOHC Engine

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190K views 159 replies 80 participants last post by  BlackGTP  
#1 ·
Ive had it, this is the last straw (this is going to be a rant, just to let you know.) Im a college student at the age of 21, Ive had my pickup (God bless that thing) since I could drive. I got this 1995 Monte Carlo 3.4L DOHC this past summer becasue i needed better fuel mileage, truthfully my mom bought it without my consent or checking it out, so I was hosed, and now im out $1500.00. What a great wrapup to 2006 and a sh*thole start to 2007 :
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Ive replaced a camshaft sensor($95), 2 O2 sensors($50, second one was under warranty), 3 vaccum lines ($5), an intake gasket($20), a fuel regulator($50), PROM chip(#75), and an injector($90). This car has been nothing but trouble.

Ive been battling an idel issue with this car that is known with this engine. I solved the problem today, after 3 months of testing it. The O2 sensor went bad for the second time, and I had to update the prom chip. From what Ive read online and through many forums I am a member at, I am the only one whos solved this problem, for that I am very proud. But today a plate in the tranny went out. I cannot afford nor do I want to put any more money into this car. I was planning on getting it running and selling it this summer.

The 3.4 engine is the worst engine GM has ever built, and the T4 transmission paired with it is the weakest too. This car does not deserve the bowtie. Im so sick of this POS monte carlo.

I am a huge GM/chevy fan, I have a bowtie wrapped in barbed wire on my arm, but this series car/motor/tranny is the wost I have ever come across.

Im attending college right now, i have no money, i cant afford a new car. I have to drive the truck, at 11-13mpg im going to take a hit in gas during the school year and in summer when i drive 40miles a day roundtrip to work. 2007 is becoming 2006, a horrible year. My parents are going through a divorce, its dragged on for a year, the house is going to be sold.

DAMNIT!!!!!!!!!!!!!!


end of rant.

(i don't expect anyone to reply... i just needed to get this out....)
 
#30 ·
I love the Twin-Cam 3400's but would never own one myself. My dad's a mechanic and that motor is one of the worst motors to ever come out of Gm right along with the first couple years of the Quad 4. Although I know of a 1992 Cutlass Supreme Convt. with the 3.4 and it hasn't given the guy much trouble. Pretty much with any car you can get a good one or a bad one. It's just the chance that you're more likely to get a bad DOHC 3.4 than a bad 3800. My dad's '90 Grand Am with a Quad 4, one of the most notorious GM engines, has been trouble free for over 140,000 miles.
 
#32 · (Edited)
Sorry to say this Broh, but I think everybody has had a bad used car experience. Consider it a right of pasage as well as a learning experience.

I do understand how this has been the cherry on your 2006 cake, and for that I sympathize.

After my own learning experience I decided that reliability was more important to me than gas mileage. I may burn more gas, but I pay less in repairs, so in the end it probably works out to the same - except I have a working vehicle for a greater percentage of the time. That was my logic when I ordered my 9C1 and I've had success with this approach for almost two decades.
 
#33 ·
Tomko said:
Sorry to say this Broh, but I think everybody has had a bad used car experience. Consider it a right of pasage as well as a learning experience.

I do understand how this has been the cherry on your 2006 cake, and for that I sympathize.

After my own learning experience I decided that reliability was more important to me than gas mileage. I may burn more gas, but I pay less in repairs, so in the end it probably works out to the same - except I have a working vehicle for a greater percentage of the time. That was my logic when I ordered my 9C1 and I've had success with this approach for almost two decades.
I know im not alone yes. But since i was almost forced into this car, it really pisses me off.... I will not let it happen again. I will buy my own car, and if its just as bad as this (which it wont be thankful to my somewhat mechanical skills and knowledge) then its my own fault.

Tomko, did you see you made my avatar??? pretty sweet huh?
 
#34 · (Edited)
#35 ·
Flippin sweet! And your quote in my sig is perfect. I have alot of people wow at the fact that I "branded myself" with the bowtie. But no matter where GM goes in the future, I will be right behind them.

People ask: "What happens if GM falls?" (about my tattoo)
My reply : "To remember the good ol' days, when cars were bold, engines were big, rwd was the powertrain, and haulin ass and kickin @$$ was America's past time!"

I may only be 21 years old, but I have a local mechanic who thinks very highly of me. He's always there to help me out and teach me things, for that I am greatful. He's so proud to see "kids" that are interested and know more about cars than just putting rims and exhaust on, becasue lord knows that all they are up to (ricers). Needless to say, I am one of them who excells and enjoys cars, working on more than just exhaust and rims :) He has taught me so much knowledge. But I have to give credit to GMI and ChevyTruckWorld Forums for expanding my knowledge greatly. These communities are so great, whenever I have a problem I consult my mechanic freind and then the forums whenver I get stuck.

Things do get out of contol on here sometimes, even I know I have contributed to it, but take the good with the bad. This is a way more positive to this site then negative.

I am actually in the ITM program at UW Stout, Ive got my 2year degree at Dakota County Tech in Minnesota, and Im completeing my BS at Stout. Before I went to college I had to make a choice, cars or computers, I chose computers. But I will always be into cars, I love to "tinker" with them and help other people out. Ive actually had alot of my freinds (well the girl ones anyway) that have trouble come to me, which makes me feel good that they trust me to work on their vehicles!

GM down to my Bones!
 
#36 ·
ChevroletTough said:
Flippin sweet! And your quote in my sig is perfect. I have alot of people wow at the fact that I "branded myself" with the bowtie. But no matter where GM goes in the future, I will be right behind them.

People ask: "What happens if GM falls?" (about my tattoo)
My reply : "To remember the good ol' days, when cars were bold, engines were big, rwd was the powertrain, and haulin ass and kickin @$$ was America's past time!"

I may only be 21 years old, but I have a local mechanic who thinks very highly of me. He's always there to help me out and teach me things, for that I am greatful. He's so proud to see "kids" that are interested and know more about cars than just putting rims and exhaust on, becasue lord knows that all they are up to (ricers). Needless to say, I am one of them who excells and enjoys cars, working on more than just exhaust and rims :) He has taught me so much knowledge. But I have to give credit to GMI and ChevyTruckWorld Forums for expanding my knowledge greatly. These communities are so great, whenever I have a problem I consult my mechanic freind and then the forums whenver I get stuck.

Things do get out of contol on here sometimes, even I know I have contributed to it, but take the good with the bad. This is a way more positive to this site then negative.

I am actually in the ITM program at UW Stout, Ive got my 2year degree at Dakota County Tech in Minnesota, and Im completeing my BS at Stout. Before I went to college I had to make a choice, cars or computers, I chose computers. But I will always be into cars, I love to "tinker" with them and help other people out. Ive actually had alot of my freinds (well the girl ones anyway) that have trouble come to me, which makes me feel good that they trust me to work on their vehicles!

GM down to my Bones!
I'm twice your age, but when I read your latest post it reminded me a lot of the young man that I was.

I too was faced with a choice between working with cars and a career in a less interesting field. I chose the less interesting field, in part to achieve a better family life, but now earn a good enough living to still enjoy cars.

Your desire to learn and keep on learning is an outstanding quality, and one that will take you far in life. I truly believe that you can always learn something from someone. It may be what to do in a certain situation - or it may be what not to do - but you can still learn.

You have the ganas and for that I salute you.
 
#37 ·
When I graduated out of college I wanted a Grand Prix as my first big purchase (91 ;) ) - I tried to hold out for the 3.4 engine but it kept getting delayed so I bought a 91 SE with all the trimmings (looked like the 3.4 GTP) w/3.1 engine.

Im very happy I didnt get the 3.4 afterwards - though the 3.1 did have the dreaded oil leak :(
 
#38 · (Edited)
The problems with the 3.4L DOHC were mainly peripheral (Chevrolet Tough, your engine issues are not out of the ordinary on any motor of that vintage and none sound fatal), the main mechanicals were very solid, but it was much more complex and difficult to work on than the OHV's of the time and more costly to maintain for that reason. As for the timing belt, many Japanese motors also have belts that need replacement every 60K or so, as well as most Audi motors. I think the weakest link with the 3.4L DOHC, as you unfortunately have experienced, was the tranny. But back when it came out, 215 bhp and a 6700 RPM redline from a naturally aspirated 3.4L V6 was a big deal, and it sounded great as well.
 
#39 ·
I would go as far to say that the 3.4 is a powerful engine for its age. But the tranny was junk from the start. This motor has so many potential problems. Mainly the ones ive come across. The cold start issue is a major problem that no one realy knows how to fix. The cold start issue is not quite fatal, but not good. It burned ALOT of gas on startup, so much i noticed the a difference on the gauge. Not to mention the rich smell, no power to the brakes (yikes!) and horrible acceleration until it warmed up. As far as i know, ive had the most success, some days it would run fine, but most of the time it'd run like crap. The PROM update seemed to help somewhat, and a new O2 sensor. Thought i think the harness that runs from the O2 sensor to the computer is actually the main problem.... I will never know, i feel bad for anyone who has this motor..... get a 3.8.

All and all, Ive learned more about cars from this experience. Ive pulled the computer on this car about 9 times... (don't ask) and so many other things, some of it just simple troubleshooting with simple and complex tools.

It was an expensive lesson.....
 
#40 ·
Xenon said:
Nothing wrong with driving an import....

That out of the way you could get a Fireo for dirt cheap with the 2.8.
Not a good choice for a daily driver. Hard to work on, expensive to have others work on (assuming you can find a garage that will actually work on a Fiero, seems like most garages despise them), not very reliable, and with the 2.8 you don't even get good gas mileage.

It'd be fun though.
 
#41 ·
The 3.4 TDohc is, I think and sweet ass engine. I own a 3.4 and I never have problem with it. I also got two Luminas with 3.1 and they havent given me a problem since Ive owned them. 3.4 and the 3.1 have the same block. I would never get rid of mine, specially after kicking the crap out of ricers and them finding out that a lumina just beat them.
 
#42 ·
Picking among lower-mileage used GM 3.8s, something like an 02 LeSabre maybe that was probably used lightly, is a lot of bang for the buck. Most LeSabre types will have ABS and they also have automatic load levelers for the nights you have to transport the kegs.
An SC GP on the other hand is more likely than not to have had a lot of hard running. Not all of them, I see quite a few driven by old folks. But their kids probably run the pith out of them when given the chance.
 
#45 ·
LAMRONH said:
An SC GP on the other hand is more likely than not to have had a lot of hard running. Not all of them, I see quite a few driven by old folks. But their kids probably run the pith out of them when given the chance.
My old fok dad has an SC GP and he drives the pith out of it :D :D He lopes down the highway at 70 but he gets there very quickly :D :D



 
#46 · (Edited)
GMOnlyForMe said:
The 3.4 TDohc is, I think and sweet ass engine. I own a 3.4 and I never have problem with it. I also got two Luminas with 3.1 and they havent given me a problem since Ive owned them. 3.4 and the 3.1 have the same block. I would never get rid of mine, specially after kicking the crap out of ricers and them finding out that a lumina just beat them.
its a powerful engine, but it is very problematic. The 3.1 is a strong engine, has less problems, and less design flaws. You should feel blessed by the car Gods that you haven't had a problem with your 3.4. They are the worst engine IMO hands down. Don't get me wrong, i like the monte, but the engine tranny combo, sucked horribly. It nickle and dimed me to death, and I know for a FACT that I am not the only one.

I will never own a 3.4L DOHC engine again.

Life lesson: dont let your mom find you a car, second, reasearch the hell out of the car before you buy it. I know so much about the 3.4 DOHC now its funny, knowing all of it, I wouldn't buy one. Not to mention the hours ive spent out in the garage freezing and tooling.....

Damn you 3.4....Damn you
 
#47 ·
You couldn't give me a GM car from the 80's or 90's. My '97 Saturn is just barely okay, it has had a lot of little niggles that bother me, enough to where I'm entertaining the idea of a different car even though it's running fine at the moment.

Yikes, dark days for the general. I'm not really a fan of any corporation (blind loyalty = foolishness), but I do pull for them to move back towards the standard of the world that they once were. I firmly believe that America and Americans can make the finest anything in the world if we really try.
 
#49 ·
How many miles were on the car? Does it look like a hard life? If the car wasn't used all that much then I'd be quite upset... but if it's been horsed it's whole life by the previous owner, maybe it's not the huge dud you think it is. I looked years ago for an early 90's 3.4L Lumina Euro (the older style), and couldn't find one that hadn't been driven to hell and back.

Not that that matters in the end... if your car's dead your car's dead, no matter what the reason. Get an 80's Grand Am or Cutlass Calais with a Quad4... zippy little cars with no known engine problems ;)
 
#50 ·
140,000 miles on it. The car looked maintained. But who knows? The tranny fluid was a little dark when i bought it, but nothing bad....

Im probably going to be looking at a 2000-2001 grand prix. 4door GT
 
#51 ·
paul8488 said:
How many miles were on the car? Does it look like a hard life? If the car wasn't used all that much then I'd be quite upset... but if it's been horsed it's whole life by the previous owner, maybe it's not the huge dud you think it is. I looked years ago for an early 90's 3.4L Lumina Euro (the older style), and couldn't find one that hadn't been driven to hell and back.

Not that that matters in the end... if your car's dead your car's dead, no matter what the reason. Get an 80's Grand Am or Cutlass Calais with a Quad4... zippy little cars with no known engine problems ;)
I heard Quad4's eats head gaskets like MAD.
That was really the only trouble spot i was able to determine....and that was after reading about how unreliable those engines were. Well that and those engines apparently run rough and noisy.