My engine has only been started a few times after being rebuild, and it's always idled around 1500-1600 rpm. I thought it was just cold but today I ran it for about 10 minutes and it never changed. I am running without a MAF, but I don't think that should affect it. What could cause this? I don't see any vaccum leaks. I tested the IAC motor from shoebox's instructions, there is resistance of 40 (first time i checked it) and 70 (second time) between A and B, and C and D. But I have no connection at all (says there should be no resistance) between B/C and A/D. Is this my problem? Could it be something else like the TPS?

 

Could be any of these.

IAC stuck open
Vacum Leaks
Stop screw on TB open to far.

TPS voltage will have nothing to do with what your idle speed is. The motor is either physcially getting to much air past the TB or your demand idle speed some how got set to high via PCM programming.

 

The stop screw is ok, the pcm is set to idle when its warm (and it was fully warmed up) around 750-650 (I haven't changed it). How can I fix it if its stuck open? Maybe its stuck all the way to the max that's why its around 1500 rpm?

 

I just looked at a previous datamaster run, TPS volts is .67 at idle, raises to 1.37 at 21% throttle, IAC position moves around 60-80 or so, it says idle rpm 788 but the actual rpm is 1500-1600 the whole time.

 

IS that the demand idle speed or actual idle speed on the scanner?

 

Check your vaccum lines with a vaccum tester. Or see if all the lines are on properly.

 

No resistance means no connection, so no problem there.

If you have a stock cam, IAC counts should be under 40 at hot idle. The extra air that you are getting will cause the idle to be higher. You may have a rich condition that is causing the IAC to add more air.

 

what does the scanner read under DESIRED IDLE?

if its 788RPM, then your IAC motor is toast

 

The 788 is under "Idle RPM" in datamaster on the right column near the bottom, I think this is what it's shooting for. The RPM in the top left column (and what the engine sounds like) is the higher 1500-1600. I'll check to make sure the vacuum lines have no leaks.

Shoebox, doesn't no resistance mean there is a perfect connection? My voltmeter reads there is an open/no connection on those wires, so thats good if thats how it should be.

Yes, it's the stock cam. In datamaster it looks like when you rev the motor the IAC goes up a little (around 80-90). Then very slowly goes back down to about 60.

I'm going to check again and see if I can tell by the O2 sensors if it's rich, before it wasn't in closed loop yet.

Thanks all for the ideas

 

I guess I was meaning no resistance reading (infinite resistance). You are correct. I will see what I can do about making that clearer.

 

I found that after I cleaned my TB, the blades would not fully close causing a high idle. I could not see that the blades were hanging open, but when I lubed the blade rod (at the corners where the rod enters the body), the high idle disappeared.