NEED HELP!!! ENGINE BUCKS UNDER LOAD!!

[94oldsdohc]

Last Saturday while taking a sharp turn, the engine started to miss and it went away afterwards. Later in the afternoon, everytime I accelerated from a dead stop, the car will start to buck like a wild horse. I will ease on the accelerator and then the engine speed will increase. However, everytime I have to climb a hill, the car will start to do the same thing again.

I replaced the plugs, wires, fuel filter, PCV, air filter and also replace the intake gasket. The problem goes away after the sits overnight, then after a while, the problem symptom returns. Today, I replaced the fuel pump with a NAPA unit, did not replace the dampener, after driving the car for about 5 miles, the problem returned again!

Do I have a defective pump? I will be doing a fuel pressure check tomorrow, nevertheless, it appears to be lots of pressure when I depressurize the fuel system.

I had a Code 42 that came on when I jumped the fuel pump at the test harness and drove the car to bypass the relay. It cleared after disconnecting the battery.

I am lost and would appreciate any suggestions what to look for.

The car is a 1991, Pontiac GTP, 3.4 DOHC, Automatic.

Thanks!!

[blk92z34getrag]

**EDIT** Nevermind I am obviously blind.

[SappySE107]

It could also be the injectors got messed up. Filter is easier and cheaper but I would think about the injectors next.

[twixt]

mine did that horribly till i replaced the control module and packs, and crank sensor(god that sensor is a bitch.) now it just missed and stalls a lot. f-in POS lumina z34s im getting code 42 now and idk what that means i need to do.

[twixt]

after getting new control packs and module. it would stall and miss sometimes so i got a computer and the problem seems to be fixed.
i did the computer because it was still telling me the module i just replaced was the problem, and yes it was still giving me that code after i reset it. so bottom line it works now yay idle is still low

[94oldsdohc]

Replaced the ignition module and coils, the problem dissapeared for a while, nevertheless, it came back again. I do not have any codes, but the problem appears when the car reaches normal temperature. So, I replace the temperature sensor. Now the car starts and runs, but when I put the car in drive, the car dies. When I restart the car, sometimes it will miss and backfire, and it runs okay idling, but as soon as I put the car in gear, it dies. Did I disconnect something by accident? I know the temp sensor gives info to the TCC. I removed the crossover pipe to access the temp sensor. This problem is making me go crazy!!!

Any ideas?????

[stantmann]

With those sypmtoms and the backfire, it has to be the oxygen sensor on catalytic converter ort theconverter itself. Not that big of a deal with a 94. Just unbolt it (or cut the bolts off) and replace the sensor first, and then the converter. Usually as clogged converter will cause a bad sensor, so since this had been going on awhile, you will probably need both.

[94oldsdohc]

Well...the saga with this car still continues...

To this day, have replaced the following:
Spark Plugs
ICM
Coils
TPS
Fuel Filter
Fuel Pump
Have injectors cleaned and flowed
Replaced the intake gaskets
Blocked EGR

The car starts right up and drives well until I floor the car or is under load; it starts to miss, pop and backfire. I replaced the ECU with another one from a friend, and nothing changed. the next thing in the agenda is to replace the plug wires with the correct ones. I had replaced some of the wires with a set for a 1994 DOHC, however some of the wires were short and could not replace all of them. There are no computer codes. The EGR had been replaced with a new one, however it continued sending a code and now is blocked.

Am I missing or overlooked anything??? I checked the timing belt and it is not frayed and it is not loose.

Help is appreciated!!

[stantmann]

I told you what it was...
With those symptoms and the backfire, it has to be the oxygen sensor or the converter itself. Not that big of a deal with a 94, no cutting of the converter is needed. Usually as clogged converter will cause a bad sensor, so since this had been going on awhile, you will probably need both.

You can get to the sensor under the car, and the converter theoretically will just needa few bolts removed.

I was mistaken earlier, there is not an o2 sensor on the converter for 94's

[pbui3057]

I had the same scenario when I took a corner really fast. I've got the exact same problem except mine feels like it is bucking when I am cruising. It seems to be really bad around 50~60mph and in OD (approx less than 2000rpms?). If I leave it in D and above 60 it feels fine. Accelerating in general feels pretty bad lately. Did the O2 sensor work for you? I haven't had it fixed yet.

[pocket-rocket]

You guys will be amazed at what a clogged cat will do. Ever run around for a while and then try to breath through a straw? That is what your car feels like with a clogged cat. Reach under the car with a hammer and tap on the cat. I have had two go bad and they both came apart on the inside and started to rattle.

[pbui3057]

How do you check if the cat is bad? I just went outside with a hammer and tapped on the cat and it made a ringing sound, not a rattle. Are there other checks for it? Thanks alot!

[pocket-rocket]

How many miles is on the car? I think I heard something like a 100k mile life expectancy out of them or something like that. The only other way would be to take it off and look through it, which I would not recommend unless you have a welder and can weld good enough to put it back on. Maybe get a backpressure gauge and put it on the car to make things easier?

[pbui3057]

OK thanks! The car has around 115,000 miles on it already. Thanks for the quick replies.

[pocket-rocket]

No problem. I at home bored off my ass, so I had nothing else to do, lol.