'94 SL2 Intermittent Rough Idle in Gear

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07-23-2009 | 07:06 PM

Luvitinak

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Joined: Jul 2009

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'94 SL2 Intermittent Rough Idle in Gear

Hello! My daughter and I have restored a 1994 SL2 . It has a new short block, head, and exhaust with Cat. We finished the mechanical back in October, and replaced the interior and paint over the winter and spring. We had filled the tank and drove the car approx. 60 miles. The car basically sat for about seven months, inside the garage, and outside in cold weather. We drove the car the other day for the first time. The car runs fine, but intermittently idles rough in gear. I added octane booster and drove the car on the hiway until it was empty and filled up with high octane fuel. It still idles bad in gear. Okay… Tech stuff… Vacuum gauge shows 17-20 hg. When running good , 5 hg. When running rough. When you shift the car into neutral it idles up to about 2,000 rpm and slowly goes down to 750-800 rpm. (acts like a vacuum leak!!!) I have checked for vacuum leaks everywhere, I even resealed the throttle body with a new gasket. It has a new IAC, MAP, EGR(non linear), Ignition coils, IAT, O2 and CTS... scan tool shows engine temp to be on the money. I even flushed the injector rail with a carbon clean machine, and ran 1L. of cleaner through each injector wide open. The cylinder compression readings are 175 psi. each, and hold for awhile. Drive cycles have been learned, and fuel trim is normal. Anyone have any ideas??? I’m pulling out my hair! The only thing I can imagine is possibly random ignition module timing issues or sticking valve!?! Oh…It does it hot or cold, open or closed loop, and NO SES light/ or codes. I’m pulling the head off Friday night. Sorry for being so long winded! I know how easy it is to over look something obvious when you over think things. I hope thats all that I'm doing! Thank You for your time!!!!!