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Discussion Starter #1 (Edited)
whoops, i meant to say that the car had a "stored code".....hi everybody, my car started to idle rough in park and drive, with a surging ,loping sort of idle. i have already replaced the iac valve by the way. in any case ,after hooking up the scanner to the car there were no hard codes except a.. po605.. which is translated as a "internal control module rom error" does this mean that the eec is fried or does this mean that the performance chip im using is shot? let me know what you guys think when you get a chance. thanks in advance for the assistance. kind regards, jeff
 

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Discussion Starter #3
the car has been having this strange surging or pulsating low idle while in park and neutral, however when in gear and under power the car performs well. all this started about 1 week ago or so, and after spending a couple hours at the shop we were still unable to pinpoint the issue. heres what i can tell you that we did find....

the fuel trim was bouncing around between 1 and then would drop down to about a negative 2 or so. also, the tps voltage was about .094 at the scanner, and about 1.004 "live" or taken right from the sensor itself. shouldnt both the scanner reading and the reading taken from the tps be somewhat the same? fuel pressure was about 34 psi. i really hate to just start throwing new parts at the car since thats going to add up real fast. maf has been cleaned, iac has been replaced, 02's seem to be working well,egr is also working at this time,and there does not appear to be any vacuum leaks anywhere, nor are there any other codes at this time. the car has been upgraded with a pi conversion and im using a reinhart performance chip.[sct tune]. the conversion and chip were installed about 2 years ago,and all has been running well until this b.s. started.

whats odd is that the car idles fairly well in gear, and under acceleration there is no miss or anything unusual but in park and neutral the idle is struggling to catch itself. also when the car is revved up as soon as the rpms drop the car sounds as if its going to stall, then it catches and starts back into this surging loping routine....what gives??:confused:
 

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Maybe you have a vac. leak. Either that or maybe try cleaning the MAF? Then reset the EEC and let it re-learn everything and see if the CEL comes back.

Jay
 

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Discussion Starter #5
no cel ever came on and the computer has been reset. no vaccuum leak was ever discovered. the fact that the car only seems to idle poorly in p/n and runs well other than that, would probably rule out a vaccuum leak? this is a real p.i.a. to try and figure out so im open to all suggestions..... regards, jeff
 

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Discussion Starter #6
well, just found out that the "po605" [internal control module rom error], is sometimes normal for those using an after market chip. the code itself is just a result of having the chip in place on the eec and does not neccesarily mean that theres a problem with the eec, or chip.

so, with that out of the way, the idle-surge problem becomes even more difficult to pinpoint. :confused: :confused: :confused:
 

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Check the MAF and air temp sensor.
 
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