I have a 90 Z24 with the 3.1- 5 speed. It's been really great until lately.

It doesn't matter if the engine is hot or cold, or what gear i'm in, or what speed I'm going. I will accelerate from a stop and immediatley once i let the clutch out the car will buck. Not surge or hesitate, but buck. It will do the same thing cruising down the highway. It starts bucking out of nowhere and usually stalls out.

It'll usually restart and idle fine until you go try to drive off again.

When it was doing this one time I pushed the clutch in and tried to hold the rpms at a certain point and the rpms were jumping all over the place. The throttle had a mind of its own.

I give the car a few minutes and I'm able to drive off. It'll act great until this problem appears again. It could appear 5 minutes later or not until later that day. Really sporadic.

No trouble codes.
I tested the TPS and the voltage as fine.
Changed the plugs and wires. - thought i fixed it, but it came back again.

Where should I start in trying to track down the problem?

 

possible ignition module or maybe even a plugged cat converter. could even be bad gas, dirty fuel filter/injectors... lots of things it could be. What did your old plugs look like?

 

sounds like a ign module a common and easy fix

 

The plugs I pulled out were a little sooty. Nothing severe though.

I threw some injector cleaner in today. Was going to swap fuel filters but couldnt get the old one off, gotta spray it down.

Maybe I'll get the cat hacked off. I just hate randomly replacing things not knowing if it'll fix the problem

Reading some Z24 boards the ICM does sound fishy. I'll check on the price.

 

What happens if you leave the digital EGR unplugged?

Edit: Nevermind, didn't matter, the bucking is still there. I'm gonna f*ckin lose it soon. Took 40 minutes to get home when it should take 10.

An ICM and new Coils are $400. I'm tempted to buy em. Even if the car is only worth $1000. I need a driver and can't afford a better car.

If that doesn't work I'll pull a Carrie and everything is gonna go up in flames.

 

Update:

I replaced everything in the ignition system. Plugs, wires, crank sensor, ignition module, and coils. Didn't fix the problem.

So i replaced every sensor in the engine bay. The tps, egr valve, idle air control, map, air temp. Nothing, still bucked.

Last ditch effort I replaced the ecm and its working fine now. So i'm hoping that's it.