Bucking 92 Lumina 5 speed and other problems

[Kyles93Z34]

Well i got my 92 Lumina Z34 5 speed today. When you shift into 1st at around 4 grand the car starts bucking terribly. It does this also in 2nd at the same RPM. It seems as if it has a rev limiter at 4 grand. If you let your foot off of the gas and allow the car to idle it bucks severly some times in second and third also. Not all of the time though. What might this be?

Kyle

[93gtpdohc]

sounds like you got a fuel problem, i brought a 92 gtp 5spd, and it had the same problem, i just put another set of injectors in and it fixed the problem,

[Kyles93Z34]

The people i just bought it from said that they just had the injectors cleaned last Tuesday. I hope it is nothing major.

Kyle

[SappySE107]

Check your computer and see what chip you have. GM revised their chip to take care of this problem but it may be something else as well.

[HayesPerformance]

He's Right!

That is very true. In my GM code referance book for ALL vehicles, for each year the codes release all have different characteristics or problems for that matter and through out the year are revised to a better CODE.

Regards,
David Hayes

[Kyles93Z34]

Isn't the computer under the coolent overflow tank? How hard is it to remove the tank? While i have the tank out i might buy your chip if the car doesnt already have a chip.

Kyle

[Mach10]

Hmm...
With the clutch in, rev it in neutral... Does it bounce around at 4k as well?

Could be that your clutch/neutral switch is jammed closed... That would make it pound off the 3500-4000 redline the ECM forces while in neutral.

[SappySE107]

That doest exist in the 5 speed codes. There is no neutral/park rev limiter at 4000.

[Mach10]

Ah... So I'm backwards? The neutral cutout is in the auto codes?

Hmm... Bucking at specific RPM? If it does it consistantly, it could be an ignition module or coil problem.

Problems at WOT usually mean a fuel delivery or spark timing problem, as most of the emmissions controls don't do a whole lot.

Check to make sure you don't have a plug wire (or 2) crossed. That'll ruin your day for sure

[Kyles93Z34]

Yeah i know about the plug wire things. I was driving my old auto Z down the road and all of a sudden it started bucking wildly and didnt want to run under any amount of throttle. I popped the hood and one of the plugs had jumped out!!!lol.

Kyle

[Kyles93Z34]

I think the problem might be the injectors after all. I noticed that it isnt necessairly 4500 but when it is full throttle. Is it getting too much gas or not enough? I priced new injectors and lets not go there... .

Kyle

[Kyles93Z34]

Had the injectors cleaned and new plugs and wires put on. It still does it but not as bad. I was told it was the calalytic convter by one mechanic and i was also told it was the o2 sensor by another. I am inclined to believe it is the o2 sensor because it also seems to be running very rich. It smokes under heavy throttle only when the check engine light is on, so wouldn't that be the o2 sensor. It this is it, how much would a new one run? Thanks.

Kyle

[series8217]

They're like $15. If it hasn't been replaced in awhile it needs to be done anyway.

[Fierobsessed]

Really does sound like the catalytic converter is shot.
Consider having that replaced anyway even if it isn't THE problem.

Also, those symptoms are simular to what would happen if the cam's jumped a tooth or two, or if the injectors are shot, or if the ignition is acting up. Actually a lot of things can cause bucking and false rev limits.

[Kyles93Z34]

Replaced the cat, it still does it, just not as bad. I think it is the o2 sensor because you can smell the gas coming out of the exhaust. I will change that and if that isnt it than i will be very pissed off.

Kyle