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95' monte carlo 3.4L DOHC engine issues?
My 19 y/o son just got a $900 beater from a private seller. Since I am in a mechanical field (welder) I get the job of trying to diagnose and fix his car. This is what I have observed/witnessed. Engine will start 50% of time normally and idle at 1200 RPM. Other 50% it will turn over but not fire. While running, regardless of RPM or vehicle speed, engine will kill at random. Check engine light DOES NOT COME ON. This vehicle has a OBD 1 connector without pin "B" on the 12 pin data link. Jumper wire will not work. I am told that a code reader is useless, as the check engine light is not coming on to show a fault that will have a relevant code. After several evenings of friends and 12 pack(s) of beverages, I have learned the following: 1- I hate this engine. 2- Steve drinks way too much. 3- It is NOT the fuel pump, fuel pump relay, fuel filter, O2 sensor, vacuum leak, injectors, MAF sensor, IAC valve or loose connections on the battery (thanks to my wife for the last suggestion). If it was mine, I would turn the car into landfill food, but he (read WE) can't really afford to be out $900 and a car. Any suggestion? Even really off the wall ones would be appreciated. Thanks.
6 Answers
- done wrenchingLv 71 decade agoFavorite Answer
Those engines are bad news, as you are finding out. Dump it, before you have to do repairs, such as alternator, oil pump drive reseal, timing belt etc. Here' a suggestion. Next time it cranks but does not fire, look at tach while cranking it, it should read cranking rpms.(400 maybe). If it doesn't you might try a d.i.s. sensor. It may be on firewall side of eng block right above oil pan rail. hard to get to. It is accessable from under car.
- 1 decade ago
Either a crank sensor or an injector shorting intermittently.
Pray you never have to replace the alternator.
The story I heard from a former GM employee is that when they devoloped the DOHC motor, it made enough power to break the transmission but GM brass wouldn't let them spend anymore money to develop a better tranny so they detuned it making it just another V6....just 20 times harder to work on.
- marvinLv 41 decade ago
sorry to say that is one of the worst engines gm ever put on 4 wheels , would very highly recommend talking a big hammer to it and take out 900 dollars of frustration out on it, really the timing is a joke hard to set up correctly, don't really know anyone who can set one up, might get it close enough to run but still not correctly, have known gm mechanics to give up on that particular engine, only the3,4 dohc they are junk , bad buy hurtful lesson
Source(s): 20 years exp - ?Lv 71 decade ago
One of GM's worst engines.......ever.
Is there a cam/crank sensors on them? They could very well be the culprit.
- Anonymous5 years ago
its either a intake gasket or head is cracked. pull a spark plug out and see if it is milky if not then its the intake
