I have this 93 Z24 with a 3.1 engine. It idles rough, runs rough and doesn't show any check engine light. I have replaced the plugs, wires,coil pack, complete fuel injection rails with the pressure regulator, IAC,TPS,throttle body. I just replaced the ECM also. It starts fine but act as though it is skipping mst of the time, once in awhile for a second or two it will smooth out and sound great, but just for second intervals. All the spark plugs are sooty black and the thing stinks of unburnt fuel when idling. That tells me something has been set to run at a default setting but the ECM doesn't show any stored codes. I was wondering about the Crank sensor pickup for the DIS, but I don't even know how to find it. I would have thought the engine had a bad valve or two, but it smooths out occasionally for a second or two. Could Low fuel pressure be causing all this roughness?? I am pretty much out of ideas. :banghead:Some experienced help would be appreciated. Thanks in advance!

Have you performed an Idle Relearn Procedure? Its required on all GM 91+ V6s, I believe...

http://i18.photobucket.com/albums/b136/overallcoma/Misc/crankshaft_knock_vss_auto.png

Replace that sensor.

Then go fuel filter. No work? Fuel Pump.

Before you do any of that, check for any codes stored.

Have you performed an Idle Relearn Procedure? Its required on all GM 91+ V6s, I believe...
Yes and no. You "should" do the re-learn. But it'll be just fine if you drive it around for a bit and don't freak out when it stalls a few times.

Have you performed an Idle Relearn Procedure? Its required on all GM 91+ V6s, I believe... How do you do the Re learn process...never heard of that one before..? I will try anything (probably everything) at this point. Thanks!
OverAllComa; which sensor are you saying to replace? Or do you think I should replace both from the start? Thanks!
I appreciate the experienced ideas!

Look under the post definate fix for stalling while braking I posted how to do it in that thread. I had to do it to my 89 and also another problem I had was the solenoid on top of the charcoal canister might be worth looking into if you got one

http://www.automotiveforums.com/vbulletin/showthread.php?t=566069 here it is for you.

Look under the post definate fix for stalling while braking I posted how to do it in that thread. I had to do it to my 89 and also another problem I had was the solenoid on top of the charcoal canister might be worth looking into if you got one Thanks for the input, but there must be a different set of rules for a 5 speed..?
I did find something else yesterday, but I am not sure how important it is.... I was looking for the Crank sensor and was following the Purple and yellow leads that go to it and there is a spot where wire were protruding from the protective tubing right where they pass between the altinator and the PS resevoir. I noticed a shielding wrap was originally around those wires, actually there were 3 wires in under that shield, Yellow, purple and a solid bare wire. I know from other applications that shielding metalic material wrapped around wires is usually meant to keep out or keep in RF leaks (radio frequency). This shield is shown in the wiring schematic in a Haynes manual. How important do you supposed that shield is?? It is no longer wrapped well around those wires, so I am thinking the signal from the crank sensor, on it's way to the DIS, maybe getting corrupted or something like that. I don't know just how important that is and I don't know if I can relace that section of wire without replacing a major section of wiring harness...??
I am thinking I will go to the junk yard and try to get one of those crank sensors and the wire section that is damaged...??
Still need the Idle relearn procedure for 3.1l with a 5 speed manual trans.
Thanks

The wiring may be worth a try sorry but I dont know the procedure for the manual trans. but I will ask a friend

That was a diagram for you to find your Crankshaft Position Sensor, like you asked for.

That was a diagram for you to find your Crankshaft Position Sensor, like you asked for.
Yup, thank you!

I found a page on the web that may help you with the idle learn procedure
http://www.xse.com/leres/efidiag/idlelearn.html
Hope this helps