TPI V8 - 1300+rpm idle

[esp42089]

Hi all,

My TPI V8 won't stay at a low idle. It starts and holds the low idle for a split second, and then steps up to 12-1300. Even when fully warm, it does this. It looks like the IAC is functioning correctly and not contributing. Any advice?

Thanks
Evan

[turbo conversion]

Try lowering the Idle Warmup Duty/Steps at 160* from 40 to 20.

Also you need to turn off ego correction at idle for now.

David

[rickb794]

As I recall on the last GM TPI I had there are 2 gaskets behind the throttle body and a passage in the lower center that may or may not be covered. I chased quite a few vacuum leaks on that system. The other large leak I found at the EGR flange.

[esp42089]

I didn't get any emails that you guys had replied. Hmm..

I'll try lowering the idle warmup duty. How do I turn of EGO correction at idle? I can't find a setting for that.

I looked for vacuum leaks with a map gas bottle lightly open while the engine idled. No detectable surging or suggestion that I have a leak. grrr... That was my first thought: vacuum leak. Not saying it doesn't have one somewhere in the horror show of gaskets that is the TPI, just that waving an open MAP gas bottle around the intake didn't result in a change, so probably not a big leak.

I ran the idle valve test mode and at a low number of steps it wouldn't change the idle (like at 30, 40, etc.), but I could get the idle to move some up at 100+ steps. I don't know how to interpret these results. I considered that maybe it was a timing and fuel thing, but my maps didn't change appreciably from 2 days ago when it was idling lower. This makes me think it is a physical problem I need to find, not a tuning problem.

One bit of info that may be crucial: I tried running Warmup Enrichment tuning (WUE) the day that the idle went high, but looking at the diff (compare) between before and after tunes didn't reveal a change. Maybe I need to open them both separately and closely compare some of the details not included in the diff (compare) function.

Evan

[ChevelleFan]

I seem to remember when looking at your MSQ before.. min # of steps to move the IAC was set at 1. Try upping that to 3 or 4.

-Dave

[rickb794]

Another gasket check is to remove the PVC valve and plug that valve cover then check for vacuum at the fresh air in port in the other valve cover with a piece of paper.

This is assuming you have pinched off the power brake hose and any other hoses that might be letting in air.

[Jarmo]

Reduce your ignition advance to something like 16 deg up to 1500 rpm and 40 kpa and test if it helps. I have less than 10 deg advance above idle rpm and below idle vacuum on tpi.