Okay so I have this '94 Z28 LT1. 140k on the odometer.

Whenever I start my car it runs and idles great. Anywhere from 5-10 minutes after I crank her up, she starts idling a little rough, almost feels like she's missing... she'll idle rough anywhere from 30 seconds to a couple of minutes with no SES light on..

All of a sudden it will idle up just a little like the A/C condenser clutch has kicked on ( my air doesn't work so I leave it off ) and then idles back down, SES light comes on and my fans kick on. When my fans kick on the car stays running at 160 degrees.

I just bought the car about a month ago, did an oil change and thats about it. I plan on changing plugs and wires soon.

Any idea whats going on here?

 

First you need the codes to determine what it is. Changing the plugs and wires is a good idea but doesnt sound like its the problem. I believe your opti spark could be going bad. do you know how new the current opti spark is?? Also it could be as simple as a MAF sensor. After starting the car try unpluging the MAF sensor and see if stays running with out miss firing or idling rough. If you give it gas it will idle rough since it will be running on the rich side. But the SES codes will help alot

 

I can't find anybody locally that will plug up the the car.. alot of their scanners will not fit it. I believe it is OBD I :\ $100 doesn't seem fathomable just to tell me the codes the car is throwing :\


I wouldn't be able to run with the MAF unplugged would I?

 

Well, I just tried what you said, Unplugging the MAF sensor seems to do the trick.. I started it up with it plugged in, no SES light and no fans. As soon as I unplugged it car almost died but idled back up, SES light came on and so did the fans. Left it running for about 10 minutes and didn't show a sign of rough idle. Should I not worry about buying a new sensor and just go straight to a Cold Air Intake? Or do I still need a MAF even with a CAI?

 

well knowing the trouble codes would help alot. This is what i use to pull codes: http://www.aldlcable.com/ then i use the software FreeScan to get the codes. Anyway when pulling or re attaching the MAF sensor the engine will react like that From what you have been saying it sounds like a MAF. The MAF is giving bad data to the computer which is dumping too much fuel causing it to run rich. This could cause the engine to run rough and miss fire. Cant say 100% sure its the MAF without the trouble codes

 

u have a odb 1.5. its a obd1 with a obd2 plugin. u might get the codes by shorting the a and b terminal on the plug in and counting the times the ses light flashes. some 94s will let u read codes that way. theres a sticky here somewhere on it. i think its on the 4th gen section under fax and tech.

 

see if you have a crack in the tubing of your intake leading to the throttle body, those plastic/rubber pieces are pieces. if even a little bit of air is leaking it can make for a rough idle, mine did that too and i changed out the rubber tubing leading to the throttle and it idles fine now

 

Unplugging the MAF forces the car to run in open loop mode and meter incoming air off the MAP sensor which sits just behind the MAF. Make sure all your intake tubing is tightened down and you're not getting any vacuum leaks. If you can pull the trouble code it should narrow down what the issue is. It could be the MAF or potentially an O2 sensor since they're ignored in open loop mode.