I have looked up this issue, and most people point to the engine mounts. In this situation every mount is new with polly bushings.

Scenario:

Yesterday it came to my attention my 5th cyl wasn't firing. Fixed that issue, and since then when driving foot on the gas or off, the car jerks. It is less noticeable in higher gears, but very apparent when in first. Around this time my speedo stopped working( new sensor, not even a week old) not sure if that is correlated though.

Everything is brand new, with the exception of a few sensors I have yet to nab, and I do get a slight delay sometimes when revving in neutral.

Feels like an air, fuel issue or possibly a sensor and was looking for some advice as ways to test different angles.

It seems to get better when it warms up, but honestly I have been busy this weekend and haven't driven more than maybe a mile at a time between home and where ever. Tomorrow I can see if warming it up helps on my trip to work.

Thanks in advance for helping....again lol

stick or auto? My 88 gt Auto used to jerk when it shifted. And it used to shift up and down whenever it wanted to, so you never knew when it was going to try to kick out on you. Replaced the trans (to a caddy 4 speed auto and 4.9L). Problem fixed!

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11 Camaro SS/RS
86 Fiero GT 4.9
84 Fiero V6 Choptop?
03 Silverado 3500 Duramax! (Stacked, Tuned, Mean as Hell)
07 Suburban LT2
09 Avalanche LT3

quote Originally posted by pontiackid86: i'm sure i could fly a plane no problem.

4 speed stick

My car will "buck" in lower gears, not sure if this is what you're referring to. Basically, the car will want to surge forward, then slow down, in a jerky fashion. Almost like the accelerator goes from zero throttle to about 20% with nothing in between, so its really hard to drive a low speed in low gear. I also have the V6 and 4-speed muncie.

Your symptoms sound very much like the drivetrain is rocking back and forth more than it should. You mention engine mounts but not transmission mounts... have you checked and/or replaced those as well? You cannot tell just by looking at them. How about the dog bone bushings? Even if you have replaced them, it's not uncommon that mounts are defective straight off the shelf. Most are made in India.

To get a better idea if it's a mounting issue, put the parking brake on, start the engine and have a helper watch whether the engine rocks while you slip the clutch in gear several times. This will alternately load and unload the mounts. If any are bad, it will show up as the engine/trans rock in the engine bay more than just a little.

The only other things that can cause bucking are worn out cradle bushings, CV joints or excessive play in the differential... though these last two problems are usually accompanied by a clunk. You can test the CV joints by raising the car, grabbing one axle at a time a twisting it with your hand while the car is in neutral and the parking brake is off. There should be no play between the two ends of the same axle. There will be some play in the differential that you'll detect, that's normal.

quote Originally posted by Bloozberry: Your symptoms sound very much like the drivetrain is rocking back and forth more than it should. You mention engine mounts but not transmission mounts... have you checked and/or replaced those as well? You cannot tell just by looking at them. How about the dog bone bushings? Even if you have replaced them, it's not uncommon that mounts are defective straight off the shelf. Most are made in India. To get a better idea if it's a mounting issue, put the parking brake on, start the engine and have a helper watch whether the engine rocks while you slip the clutch in gear several times. This will alternately load and unload the mounts. If any are bad, it will show up as the engine/trans rock in the engine bay more than just a little. The only other things that can cause bucking are worn out cradle bushings, CV joints or excessive play in the differential... though these last two problems are usually accompanied by a clunk. You can test the CV joints by raising the car, grabbing one axle at a time a twisting it with your hand while the car is in neutral and the parking brake is off. There should be no play between the two ends of the same axle. There will be some play in the differential that you'll detect, that's normal.

I will double check by putting it in and out gear tonight. Although I have had someone watching while shifting into gear just on checking a new clutch. I would of hoped he would of mentioned some type of motion.

Would bad bushings cause a surge when accelerating. I was able to play with driving a bit more this morning.

Weather was a bit colder than usual this morning. Started it up, and it actually died on me twice. Started it up the third time and revved it for a few seconds and drove it down the block to the gas station.( it did its jerking fun on the way) and it idled fine once there. I then did my 5 mile jaunt to work.

Noticed sometimes i had to rev it, then rev to put in gear or it would try and bog down on me, and once warm, it jerked noticeably less.

I hope this will give a little bit more insight into it, and I will gladly take a look at the mounts tonight, just as a side precaution.

[This message has been edited by sirtimeless (edited 05-21-2012).]

Yesterday I saw a can of "Jerk Off" repellant on The Simpsons for those of you who find a humor in that show.

Since your odometer is not working unless you've repaired the problem, the root cause of that may also be associated with the problem you are having. The ECM (not sure about the Fiero's) needs to see a vehicle speed in order to appropriately address some deceleration tables for example which can have an effect on the engine rpm when you come off the throttle as well as the rate of engine braking. If you had one cylinder misfiring depending on the cause, you may have another doing the same intermittently. I had the problem you described as a result of a bad plug wire grounding out intermittently under load and light throttle causing a sudden decel in engine speed that results in a bucking sensation that can vary with the condition of the drivetrain mounts.

quote Originally posted by Joseph Upson: It's amazing it's even running, you gotta fix the known easy stuff first in this case. Put the good parts on and see what happens.

Those are not known issues, just places other people mentioned to check with similar issues.

Figured I would take the time to at least look into each issue, and will likely replace them with new, just for ease of mind. In retrospect i wrote that post up in a bad way lol.

[This message has been edited by sirtimeless (edited 05-21-2012).]

Would that "driveline absorber" (looks like a mini-shock absorber) on the front of the engine, near the oil filter cause these symptoms if it were worn out?

That is also brand new lol.

I have this same problem; I have a 1985 SE V6 w/ the 3.4 f-body conversion and Getrag......I have had the problem since I switched to the 3.4- switched the mounts out, Polyed the dogbone on one end, swapped out all of the sensors, no codes, recently swapped the distributor and coil....Last year I swapped to an 88 rear cradle....Nothing ever made a differnce.....Lower the gear, the worse it is- I can't drive in 2nd at 20-30 because it will jerk to destruction........I have thought about doing the 7730 swap....am actually wondering if the 7730 will pass CA smog....? Anyone know about that?