gene

Joey:

I have been trying to straightened our the 92 SC you helped me with a few weeks ago. This is the tranny replacement with a SOHC tranny on a DOHC motor. By the way, your instructions were great and the job went exactly as you said. The problem I am having now is jerking and bucking when I am at less than full throttle. The car idles great and runs well on the highway at full or almost full throttle. The problem occurs when I am pulling out slowly and apply only light throttle. It begins to buck and jerk. I can correct it by hitting the throttle hard. I have the same problem when I let off the throttle when at highway speeds, although it really isn't that bad...but I can feel it. I get no indications of any codes being posted. I have replaced the temp sensor. I should have mentioned, the problem seems to come after the car reaches temperature.

A couple of other indications. The engine temperature seems to climb from less than half guage to three quarters under load. Then the fan kicks in and the temperature drops to less than half. With the AC on it seems to climb just past half and stay there unless I am in heavy traffic.

I know I gave you a lot, but this is really becoming a nightmare.

Can you help? I appreciate all you have done so far.

Gene

Joeybagodonuts

hmm, thats hard to call from your description,b ut you can elimnate the tranny, the tranny wont make it buck and jerk like that no matter what year one you put in, honestly thats usally the driver not coming off the cluthc pedal right, i just had a guy write me and tell me when he hits it and lets off andm hits it again in gear it bucks, i was like, of course it does, it wasnt menat to be driven like that!
of course, you may have a bad cyl head temp sensor which is causing it to buck, does it go away after being warmed up? it sound slike its operatiing fine according to your temp readings and description.
did you use a saturn brand clutch? aftermarket clutchs , some brands hgave been known to have a jerky engagement, finally did you use a clutch alignment tool or just finger it in there?

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Yobos4vr

was it an auto or 5speed? my 5 speed does that when i'm in a lower gear than what i should be. like going 35 in 3rd it will buck. but go to 4th and it's smooth. only reason i do that is if i know i'm gonna stop ahead then why even bother to go to 4th just to brake.

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gene

Joey:

The problem is more dramatic after it warms up. I also don't think it is the clutch since the problem was there before I changed the clutch and tranny. Let me mention that when I decellerate from almost all speeds in 4th and 5th, the engine wants to die, at least for a moment or so, them kicks back to idle RPMs. In some of the other threads I read about possibly the EGR valve. Not sure these were the sympoms. I looked at the EGR when the car was idling and pushed up on the diapham. It acted like it does on the road.

Hope you have some other thoughts.

adam92sl

From reading past posts - the EGR can act funky when you least expect it even after checking it My experience was different, I replaced the egr and it turned out to be surging from a vacuum leak.

Bizzar

ding ding ding we have a winner. I'm going with what Adam said. Here's a quick test. First make sure the engine is cold or this really hurts. Pull the small elbow off of the EGR vavle. Now push up on the bottum of the EGR vavle diaphram...all the way up. While holding the diaphram in the up position, hold your thumb over the vacuum hose hole (the one you removed) What you are looking for is if the diaphram slowly creeps its way back down. That is a sign of a vacuum leak. A properly working EGR will hold at the top. A weak spring can also be the cause of jerking and well there isn't much to test that with except years of practice You kinda get a feel for them.

gene

Thanks for the suggestion. I tested the EGR and it held vacuum. I also checked for vacuum leaks and found none. I tried another check. While the car was idling, I slowly accelrated the engine. It began to stubble and almost stall. I checked the EGR and found that the diaphram was being pulled up. I took off the vacuum hose to the EGR and tested for vacuum. It had some at idle and it increased as the engine reved higher. When the vacuum hose was off the EGR the engine did NOT stubble or try to stall. When I reattached the hose it stubbled and almost stalled.

Any idea what is happening here? Is the EGR supposed to work this way? By the way, the engine was up to operating temperature when I did all the checks.

Thanks

Ssicarman

Try this one. With the engine running, put a vacuum source to the EGR valve. Doesn't matter what is, the cheapest out there is a piece of right size vac hose connected to the EGR and the other end connected to your mouth. Start sucking. The EGR valve should have a vacuum bleed off with the engine running. You should have one hell of a time unseating the valve and pulling it up. Usually the best I can get is a slight pull up before I run out of suction and the valve reseats. If the EGR valve pulls up and the engine begins to run rough and there is no bleed down to the vacuum then you will need to replace the EGR valve.

gene

I'd like to close out this thread. The problem was a bas EGR valve. After replacing the valve the problem went away. Thanks for all the help you all gave me on this one.