first start. very high idle. lots of evap codes
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From: hampton,mn
first start. very high idle. lots of evap codes 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.
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.
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From: Katherine N.T Australia
Or excessive timing. I can make my ls1 idle at 2500rpm with the iac and throttle closed just by giving it 40deg of timing
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...
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From: Katherine N.T Australia
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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.
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From: Katherine N.T Australia
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.
EGT's are fine.. Its in CL
" 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.
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From: Dickinson, Tx
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?
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?
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From: hampton,mn
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.
Thread Starter
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From: hampton,mn
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.
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From: hampton,mn
