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Discussion Starter · #141 ·
being a employee of gm for 15 years I have to tell you that your wrong. the block used for the 3.4 is the same as the 2.8, 3.1, and 3.3. the stroke is the same and the bore is different
The block isn't necessarily the problem with the car. The design is poor, the connection between the upper plenum and block don't cool at the same rate, and can cause cracking/cooling issues. I haven't had either of these cars for such a long time. I have my 2004 silverado that has been nothing but a treat to drive and maintain.

Trust me, I'm one the biggest Chevy fans around, but I will curse the 3.4L DOHC engine until my death.

This is such an old thread....

But let me refresh. The issues I had to work on with those 2 cars were by far the hardest/worst. Its a fairly common car, with a fairly poor engine layout. The rear spark plugs all sucked to remove, the PROM chip I did upgrade but never resolved the idling issues. I even checked the spark of each plug from the coil pack with the reisitor tester. I still remember doing all of this work. I traced wires, clamped onto other to verify they were working. I had a cam shaft sensor go, the transmission in both cars blew up (i don't drive my vehicles hard, i promise. if you don't believe me, you obviously dont' know how well i take care of my truck.) Anyway I will attest to this being probably one of the worst engines that GM has ever put out. I'm glad to see it didn't continue in that manner.
 

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im going to agree that the 3.4L DOHC AND the 3.4L ohv found in the grand am/ chevy equinox are the worst motors from gm. You can also throw the 2.4L twin cam quad 4 into that mix. what a **** of a motor. we have one in my sisters Z24 cavalier never again will we own a car with that motor. the 3.4 in my moms equinox is a junk. I want even drive that car because i don't want to break down on the side of the road. gm didnt have any good motors for everyday cars till mid to late 2000. with the start of the ecotec 4 and the 3.6L all they had was the LS motors.
 

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I bought a 1996 oldsmobile cutlass supreme with the 3.4 DOHC coming up on 4 years ago. Had 65000 miles then and 90000 now and Ive done nothing but replace the brake pads. The muffler is starting to get loud and my struts are making some noise but the engine is still nice and smooth. Leaks quite a bit of oil, though.

Im a few hundred from 90k actually but when it comes up I figure Ill just need to check the fluids and change the timing belt just to be safe. I love this car/engine!

edit: boom

 

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As for as the intake manifold for the 3.4L:
I think the gasket design was changed around 2005 - before that it was a very expensive weak point.
Also, for 2007 and 2008 when they moved the engine manufacturing to China for the Equinox the entire manifold and gasket design was changed to fix the problem - only to stop making the vehicle / engine.
It is always best to buy a vehicle in it's last years of production with the oldest possible design engine and transmission - by that time the bugs are (sometimes) worked out.
I found that out when I bought my new (to me) 1988 Cultas Supreme with that equally terrible 2.8L and 100K miles. After a rebuilt trans, new injectors, leaking intake gasket and rear disk brakes that never actually worked (by design), I was fortunate enough to get that car totaled. I purchased a 1984 old Delta 88 for $700 and had better reliability over the next 2 years and was able to sell it for $600.
 

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That's a great looking Cutlass! I had a '93 Z34, between my brother and me it had over 100,000 miles on it, and we never had to do anything to the engine.
 

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I just had to jump in here, because this thread is so full of fantasy, first off I am a 21 year GM tech, 27 certfications and re certifications, 17 GM service awards, 16 GM repair innovation awards and a expert on this DOHC engine, first off yes it is alot of fun to drive and play with, but from a tech's point of view, it all ends right there, start a the bottom and go up the short block is weak and inertia components are poorly balanced, and his engine never made it to the GM performance building facility, its whole burst of power is computer based, at best it is a short life toy for backyard speed people, There is no special componets here, no forged pistons, no forged crank, heck all cranks nowadays are cut completely by computers out of semi hard billet, the only high performance is done down below was oil passages were enlarged and crank was index drilled to improve oil flow, one of the biggest problem with this short block, the oil pump is small, but it is higher pressure, unfortunately it should have been set deeper in pan, as it forthes and bubbles at high RPM, on the heads the valve bushings are in poor structure and not built for long life, do you think GM is gonna spend big bucks on a computer pumped engine?? I could go on for hours on the tech related problems with this motor cause there's lots of issues here, Tr putting a timing belt on it with out the GM cam positioning tools, the cam sprockets do not have keys in them and the sprockets should all be checked when replacing the 200.00 plus belt, cause the shafts they sit on are tapered and can slip, just a little and your performance engine is now a dog...I am not saying that someone does not have a phenomenal car with a ballistic DOHC, but having working on that engine since the day it came out till it finally was removed from the line. I give it a 2 out of 10 on the scale of great engines, and one other note for all you 3.8 or 3800 haters, it is and probably will remain the best V6 that Gm ever put out, not the fastest maybe, but nothing touches it for reliablity and long life, I know many people personally still driving them at over 600,000 miles and one at over 780,000 still purring, I don't think you will find any DOHC untouched at much over 140,000, thats enough for now, just hate seeing a bunch aof fairy tales flying around I wish they were all true too, but reality is working with them constantly. now you can bad mouth me all you want and it don't hurt my feelings much, so have at the insults, have a better day, Ya ALL.
 

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I just had to jump in here, because this thread is so full of fantasy, first off I am a 21 year GM tech, 27 certfications and re certifications, 17 GM service awards, 16 GM repair innovation awards and a expert on this DOHC engine, first off yes it is alot of fun to drive and play with, but from a tech's point of view, it all ends right there, start a the bottom and go up the short block is weak and inertia components are poorly balanced, and his engine never made it to the GM performance building facility, its whole burst of power is computer based, at best it is a short life toy for backyard speed people, There is no special componets here, no forged pistons, no forged crank, heck all cranks nowadays are cut completely by computers out of semi hard billet, the only high performance is done down below was oil passages were enlarged and crank was index drilled to improve oil flow, one of the biggest problem with this short block, the oil pump is small, but it is higher pressure, unfortunately it should have been set deeper in pan, as it forthes and bubbles at high RPM, on the heads the valve bushings are in poor structure and not built for long life, do you think GM is gonna spend big bucks on a computer pumped engine?? I could go on for hours on the tech related problems with this motor cause there's lots of issues here, Tr putting a timing belt on it with out the GM cam positioning tools, the cam sprockets do not have keys in them and the sprockets should all be checked when replacing the 200.00 plus belt, cause the shafts they sit on are tapered and can slip, just a little and your performance engine is now a dog...I am not saying that someone does not have a phenomenal car with a ballistic DOHC, but having working on that engine since the day it came out till it finally was removed from the line. I give it a 2 out of 10 on the scale of great engines, and one other note for all you 3.8 or 3800 haters, it is and probably will remain the best V6 that Gm ever put out, not the fastest maybe, but nothing touches it for reliablity and long life, I know many people personally still driving them at over 600,000 miles and one at over 780,000 still purring, I don't think you will find any DOHC untouched at much over 140,000, thats enough for now, just hate seeing a bunch aof fairy tales flying around I wish they were all true too, but reality is working with them constantly. now you can bad mouth me all you want and it don't hurt my feelings much, so have at the insults, have a better day, Ya ALL.
You got technical
 

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this is an old thread, but let me say you are totally WRONG about that. You're problem is, you don't have any money, to drive any car and repair/maintain it.

The 3.4 DOHC was the BEST V-6 engine that GM ever made, up to the time they released their "new" DOHC V-6 engines recently. I drove my 1995 GTP to 180,000 miles and just sold it for $1800- and it would run rings around the 2001 Monte SS I bought to replace it with. The 3.4 DOHC is way better than the POS 3800 series II engine, which I consider a DOG. There are a few issues that need attention with a 3.4 DOHC, i.e. change the timing belt and fix the distributor plug oil leak- but beyond that, the 3.4 DOHC is a powerhouse. If I could find another one with low miles I'd buy it and sell this Monte SS.
I have a 1995 Pontiac GTP (it is June 2021 now) with the LQ1 3.4 DOHC V6, the engine has 4500 miles on it, actual miles, the dude that bought it originally let is sit in his front yard between trees for almost 25 years. It is totally current with maintenance, and all I will say is I paid $8500 and put a new AC in it and for $9500 I have a brand new car that runs amazing, it runs better on road trips than my 2018 GMC Terrain Denali and every bit as good as my last Jag. After driving the car, I fell in love and back in 95 this body style was very bold, mine is candy apple red and literally in like a showroom car inside and close to it on the outside. We are very, very happy., would I ever sell it to an enthusiast? Maybe, but it would cost the $9500 I have in it, there are no leaks and everything under the hood is new, except the block, valves, etc.... The way this engine runs is fantastic, 26 years old with 4500 miles and does not leak a drop
 

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You got technical
the LQ1 3.4 never made it to the performance building because GM did not have a transmission that would handle this engine blown. That is a fact and can be verified by thousands of GM techs. Back in 95, they were even afraid the 4 speed auto that went into the Z34 and the GTP would not hold up so they detuned the stock engine back from 272 HP to 210 HP. That is indeed sad. With the right application this engine had plenty of potential and the manufacturer that made it was way behind the engine technology at the time with their crummy transmissions, you could not even get a manual after Pontiac offered one in the early 90's. As stated, mine is a great highway cruiser (it is 2021 now), I am talking it on a 600 mile drive this weekend back to STL, 1200 miles round trip and will leave the cruise on and enjoy the ride
 

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I had a '95 Monte Carlo Z-34. It was probably the most disappointing car I've owned. My fault, I didn't take a thorough enough test drive. The handling on the supposedly-performance Z-34 sucked. it wallowed through corners. It also seemed to have paint issues. The thing was covered in chips in a very short time.

However, the 3.4 engine was awesome.It was my first DOHC engine, and that thing pulled like a mule on highways like no OHV engine I'd had before. Going 50 mph and hit the gas, and the thing surged forward. (Funny how little 210 HP seems now, but back then it was pretty powerful.)
 
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