Car won't start when engine is warm

[richierichness]

Originally Posted by Kingtal0n

sounds like it needs tuning. when it warms up the IAT and CTS take or add fuel, you check the percentages in the software and you can zero them out for diagnosis purposes, or fix them so there is less or more as necessary.

Rough idle, then shutting off, sounds like its leaning out. the iat might be heat soaking and rising rapidly to portions of modifier where its taking massive amount of fuel out. You should be watching the wideband to confirm diagnosis. Dont tell me you don't have a wideband on a car with a standalone...

I'm running the Haltech WB02. There is no leaning at idle. Fuel trims are within 2-3% of target. IAT theory i'll look into but doubt it has anything to do with my issue since I never made changes to my map...only changes have been fuel related.

[dbeiler]

Worn coils will have a constant misfire. If they're worn (the insulation cracks and spark jumps to head instead of being routed through the plug) it'll be noticeable immediately upon startup; especially on rainy/humid days.

Any heat soak engine performance issues are usually caused by failing, heat sensitive electronics. Camshaft and crankshaft position sensors are the primary suspect.

My go-to trick is to run the engine till it heat soaks and begins running poorly, shut it off, remove the suspect component (the CAS, in this case) and pop it in the freezer for a few minutes to cool it off. Reinstall the component onto the still heat soaked engine and fire it up. If it now runs correctly for a few minutes; you've found the problem.

I'm assuming you've monitored the battery voltage and air/fuel ratio to eliminate any concerns in those specific areas.

I keep telling people: these engines are now twenty years old. If it's still on the original coils and CAS and they haven't failed yet, they are guaranteed to fail in the near future.