1994 z28 missing issues
11-28-2010, 11:50 AM
#1
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1994 z28 missing issues 1994 z28 lt1 has a miss after the car gets up to temperature. I changed the non vented opti spark out with a new vented msd opti spark did not fix the problems. Plugs, wires, iac motor, checked all grounds still have the same problem. You can't start the car runs fine for a few mins then starts missing.. I have used all my knowledge of these motors I need help?
11-28-2010, 07:43 PM
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Well whatever it may be man it sounds like its definitely coming in after it goes into closed loop. Is it still factory tuned? Check the harness and sensors (ECT, O2, stuff related directly to fuel and/or spark) to see if you have a bad connection or something close to a heat source. If you have one of the said sensors OR circuitry to one of these sensors getting warmed up TOO much it may be building resistance up, which is why i said it sounds like a fuel/spark ctrl. issue because at open loop its going to run off preset values until it gets to op. temp.
11-28-2010, 09:03 PM
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No it has a Tuned PCM in the car. Yeah when it starts missing it floods the car bad either because it is taking away spark or messing the air/feul mixture up. I didn't know if maybe the feul pressure regulator would malfunction this way? The car still has the stock coil didn't figure it would run good at all if it was the coil.
11-29-2010, 12:07 PM
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Well if its running fine until it hits op. temp like you said it rellay sounds like when it starts going off og closed loop maybe the ECT is screwed and shoing the PCM 20 degrees and dumping fuel or something? Post some sensor readings on here if you have a way to view anything or take it and get your tune checked or re-tune it. Id be looking at sensor readouts first but thats just me.
