Jason454

I just fired my all stock 2001 5.3 Silverado engine. Its installed in a 40 ford. It idles around 3k. I can't find any vacuum leaks. I have 9 evap and air pump codes. My ecu guy said send it back and he will fix it. But my question is would it idle high if the ecu thinks it has an air pump and evap crap but it doesn't? I tried 2 different throttle bodies, same thing.

Old Geezer

iTrader: (3)

Start with a list of the codes.....

2xLS1

iTrader: (25)

If the throttle blade is closed the only way for it to idle that high is for it to be getting air in it past the throttle body. It takes air to raise the rpm. Find the leak. If you can't find it, smoke test it.

macca_779

Or excessive timing. I can make my ls1 idle at 2500rpm with the iac and throttle closed just by giving it 40deg of timing

CattleAc

iTrader: (7)

Did you change the intake manifold gaskets...???


Try spraying carb cleaner underneath the intake manifold between the cyl's.


I've fixed a lot of these early 5.3 intake leaks this winter...high idle, rolling idle, lean exhaust codes...

Ed Wright

iTrader: (1)

High timing won't make it idle at 2500 to 3000, that requires air. I'm afraid you are getting air somewhere. You just need to find it.

macca_779

Wanna bet bud.. I've done it during testing

Ed Wright

iTrader: (1)

I tune cars every day. You mentioned 30 degrees here once. Many factory calibrations use 28. If your car idles up to 2500 or 3000 by advancing the timing, you have something else wrong. It takes more air to run over 2500 than it does to idle. Simple fact. If you have to pull your timing back to idle it down, you are doing something seriously wrong. Your idle EGTs are likely high at idle.

Slowhawk

iTrader: (12)

Throttle body could be hanging open too much or more than likely a vacuum leak.

93camaro_zzz

iTrader: (13)

^ This

macca_779

Show me one Ed?

EGT's are fine.. Its in CL

Ed Wright

iTrader: (1)

" CL" has nothing to do with it. Late timing raises EGTs. It takes much more air to run 2500 RPM than idle, timing won't do it. Everybody here but you seems to know this. Pulling idle RPM down with retarded timing is covering up another problem. Heck, ignore me and listen to these other guys trying to tell you the same thing.

danieloneil01

Trick someone told me about (but did it to check for exhaust leaks) that you can try for free if you have a shop vac handy.

1. Switch hose on shop vac so it blows out the hose
2. Stuff hose in a tail pipe and block it up so air can't escape back
3. If you have dual exhaust stuff the other tail pipe with a rag, towel or painters tape
4. block intake with rag or painters tape
5. put dawn in a squeeze bottle or use baby powder
6. turn on shop vac and go to town checking for leaks on the induction. Also listen for leaks.


Whens the last time you changed or checked the intake manifold runner gaskets?

Jason454

I sent the computer back to be reprogrammed. I need to do a smoke test. I can't see where there would be a leak. Throttle body is not sticking. And engine has low miles.

Jason454

Ok did a smoke test and no vac leaks. Starts up and idles good for about 5 seconds then gets higher. It idles fine if I unplug the iac before I start it? Could the iac be wired wrong? I have a name brand wire harness which I ordered for my combination. Along with ecu too. No codes since I had it reprogrammed.

Jason454

I forgot to mention I changed the iac with a known good one and same results. It seems like its working backwards. Can I swap the wires?

Jason454

Ok figured it out the green/wht and green/blk wires needed to be swapped. Idles great now.