IAC Valve Question

[t93k2500]

Yes, percentage is 0 at idle. And it is close, but not close enough. I put the original iac back in and still having the same symptoms, but it seems to be more intermittent (like it eventually idles down to somewhat normal).

 

[t93k2500]

Pretty sure there is something else going on because nothing was wrong when I removed the original (other than the pintle being a bit loose), it ran and drove fine after the throttle body rebuild. After going through the two new ones with issues, the original is back in and the issue still exists. I had a feeling in the first place that I shouldn't have fu<ked with it. Im verifying all sensors now with a multimeter.

 

[95Escahoe]

So your issue is your idle is too high?

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[t93k2500]

Just warm idle. Cold idle is the normal 1300 rpms.

 

[95Escahoe]

How high is the warm idle? And this started after you modded the TBI?

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[t93k2500]

1000 rpms give or take. When I modded the throttle body (CFM Technologies kit), I noticed the pintle on the original iac valve seemed a bit loose, but I never actually removed it. I reassembled everything, and it ran great. A week later I replaced the iac valve with the GM unit, and my issues started. Followed all the proper procedures I posted earlier, tried a BWD unit, and now the original is back in with the same issues. Using starting fluid, there doesn't appear to be any vacuum leaks, and the datalog indicates all sensors appear to be working correctly. Fuel pressure is 13.5 psi. Maybe related, but if I disconnect the battery, then go for a drive, the truck feels very powerful with phenomenal throttle response, but as I keep driving over the course of 50 miles or so, the truck begins to feel sluggish and heavy, even though fuel pressure remains constant, and the datalog remains consistant.

 

[95Escahoe]

Hm was gonna say maybe he bumped the idle speed somhow if your cap was knocked off over the years (they put a cap on the TBI so you cant adjust it unless u remove it) but it only happens part of the time, maybe someone else has ideas

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[t93k2500]

Yeah its truly odd behavior. Another interesting situation; pulled the pcv vac line, and warm idle raises from 1000 to 1400. Cover the port with my finger and idle drops to 525 (the lowest its ever idled out of gear). Thought I found the problem but putting the line back on yields no change. Rev it up, and idles back down nice and smooth. Shut the truck off and restart, high idle is back.

 

[t93k2500]

Hm was gonna say maybe he bumped the idle speed somhow if your cap was knocked off over the years (they put a cap on the TBI so you cant adjust it unless u remove it) but it only happens part of the time, maybe someone else has ideas

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Idle with iac bottomed out and unplugged is silky smooth 525. What would the chances be of a bad ecm?

 

[454/4X4]

My 94 K1500 with the same setup idles at 550 in gear HOT, and cold is about 800 in park.

Something to check...there may be a vac fitting on the back of the TB, between the 2 fuel lines...if its not in use, it will be capped, make sure the cap isnt split open or missing.