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Help Diagnose.. High Idle/p0505 .. 1998 C70 T5

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Here's the story, I had to put a starter in the C70, while it was apart, I polished the manifold, fuel rail, replaced several vac lines with silicone, new gaskets on everything, etc..

I get it all put back together and it runs fine, but throws a CEL for the Idle Air System (P0505), and one for the TPS. It is also idling at around 1150rpm warm. I check over everything and can't find any vacuum leaks to speak of. took out the IAC and cleaned it, it does seem to move freely when shaken, and when the key is turned to ignition you can feel it humming a bit. While it was apart, I did remove the TPS, and evidently somehow broke it because when I put it back on, the car was idling at 2500 rpm and had all kinds of errors. I am using an OBD2 scanner capable of Live Data, and it was saying Absolute TPS was at 100% no matter what.. I bought a new TPS and now it actually changes with the throttle.. Imagine that, lol.. It now says Absolute TPS is at 14% at idle. Is that normal? It is still idles at close to 1250 though. also, if you are traveling on the highway (55mph or so) and let off the gas to coast the throttle will fluctuate for close to 5 seconds, and if you barely have your foot on the gas but are slowly decelerating, it will kind of surge.

I drove it to work this morning and cleared the codes. I let it idle for a few minutes and the light didn't come back on, but I didn't have a chance to actually drive it. It is still idling at 1150-1200 rpm though. Should I just get a new IAC? What other things (besides obvious vacuum leaks) should I be looking for?

I am sort of getting lost. What should It idle at? what am I missing?

I should add that the car is basically stock except for n/a cams, and a V70r ecu.

Thanks in advance.

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Posted

I'll datalog my car at lunchtime to see what TPS is at idle. Edit: wasn't really doing anything at the moment, so I went ahead and checked. TPS was 9% at idle of 840 RPM. Innovate OT-2 and ARD tune.

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Posted

Huh.. So should I look at the throttle body and see if something is keeping it from closing or something?

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Posted

Also, I'm assuming that it should be around 9% with the car not running as well?

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Posted

Yea I just worked on a s70 that had a problem with high idle do to the throttle plate not closing completely. I had to adjust the rod to keep the plate closed. May not be your case but i would check to see if your throttle isn't closing all the way or is getting stuck.

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Posted

Just did this ^, lol.

Turns out that my problem is that I'm an idiot and didn't check the simple stuff. On the TB itself there is that little adjuster screw and tab that keeps the TB from shutting too far and binding. I must have bumped that while it was all apart and it was not letting it close completely. So it turns out that the new TPS was reading correctly. Once I adjusted that screw back, it idled right down to 850 rpm, and the tps reads at around 10% at idle. Thanks for the help everyone!

For reference:

2012-10-30123658.jpg

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Posted

Glad you got it sorted.

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