Stalling after cam install
Thread Starter
Instructor
Joined: Feb 2009
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From: Woodstock IL
Stalling after cam install
Hey guys I am just looking for a little advice here. I just put in a cc503 cam, 1.6 rr, long tube headers, cat delete, egr/air delete. And the car seems to idle just fine. However, when I go WOT and back off the car will stall out. Could the stock injectors and stock tune be causing my problems? BTW it is a 93 corvette LT1.
Race Director
Joined: Apr 2003
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From: moraga ca
Hey guys I am just looking for a little advice here. I just put in a cc503 cam, 1.6 rr, long tube headers, cat delete, egr/air delete. And the car seems to idle just fine. However, when I go WOT and back off the car will stall out. Could the stock injectors and stock tune be causing my problems? BTW it is a 93 corvette LT1.
Racer
Joined: Nov 2010
Posts: 460
Likes: 1
From: Oliphant Ontario
Make sure the IAC is working correctly, after part + throttle, it is supposed to open up a bit then close slowly back to an idle. There are a number of tests you can do to force it open etc to check it
Thread Starter
Instructor
Joined: Feb 2009
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From: Woodstock IL
Team Owner
Joined: Jul 2004
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From: Hartford WI
Why bother? IAC is controlled by the ECM. That means it tries to set the idle according to the programmed number. that is something that will be written in when the ECM is updated.
Racer
Joined: Dec 2007
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From: Escondido CA
Advanced
Joined: Aug 2007
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From: Hebron Il
I recomend Madtuner.com he just did a cam tune for me. He's in DeKalb so the shipping is quick,I sent mine on Wednesday and got it back Monday. A cam tune made a big difference in my car.BTW Byron opens early this year April 2.
Racer
Joined: Nov 2010
Posts: 460
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From: Oliphant Ontario
So you're saying he should just assume the IAC is OK and go after everything else? I guess IAC's never fail or gum up eh
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Team Owner
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From: Hartford WI
Not at all but until the command idle is set, and it has to be set, you can do what you want but the ECM will still try to get the same idle it was told to do with the stock program. Once he gets the new chip he can go clean the thing but if the idle is too low for the cam, cleaning and adjusting won't get you far.
Racer
Joined: Nov 2010
Posts: 460
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From: Oliphant Ontario
Not at all but until the command idle is set, and it has to be set, you can do what you want but the ECM will still try to get the same idle it was told to do with the stock program. Once he gets the new chip he can go clean the thing but if the idle is too low for the cam, cleaning and adjusting won't get you far.
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From: Overland Park Kansas
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Fare enough, but.. He mentioned that this car does idle fine, idling isn't his issue, his issue is stalling out as the motor comes off throttle and tries to drop to idle. If he can idle now, it means the engine is pulling enough vacuum to make the ECM relatively happy. An IAC that either won't move, or can't move out far enough may allow a nice idle but won't catch the off throttle change as he describes.
The IAC is the component designed to prevent stalling.
Team Owner
Joined: Jul 2004
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From: Hartford WI
Fare enough, but.. He mentioned that this car does idle fine, idling isn't his issue, his issue is stalling out as the motor comes off throttle and tries to drop to idle. If he can idle now, it means the engine is pulling enough vacuum to make the ECM relatively happy. An IAC that either won't move, or can't move out far enough may allow a nice idle but won't catch the off throttle change as he describes.
When I had the ECM reprogrammed, I reset the IAC. I shut of everything but the engine. Drive it around for a bit to get the temps up. Once it stabilized, I would set the IAC using the scanner. I would get about 20 counts. Each time I tweaked it, I rev the engine so it has to settle down again. When I get about that range, I would check the TPS and made sure it wasn't in some ridiculous range and shut down. Problem solved.
Racer
Joined: Nov 2010
Posts: 460
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From: Oliphant Ontario
The more possible cures the OP is given, the more knowledge he has to tackle the problem. Getting a proper tune on the chip most likely will solve his issues, but no one here can guarantee that and there is a lot more that can cause his described problem including specifically a dirty sticking IAC, especially one that until now, has never been asked to work in the same range it now has to.
In this case, if it idles fine but is too gummed up to back out to its max adjustment point, what do you think cleaning it will do? Certainly won't cost anything to do and very likely will add at least some improvement to how it runs.
Team Owner
Joined: Jul 2004
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From: Hartford WI
I can't define it, I am not the OP, the OP says it idles fine.
In this case, if it idles fine but is too gummed up to back out to its max adjustment point, what do you think cleaning it will do? Certainly won't cost anything to do and very likely will add at least some improvement to how it runs.
In this case, if it idles fine but is too gummed up to back out to its max adjustment point, what do you think cleaning it will do? Certainly won't cost anything to do and very likely will add at least some improvement to how it runs.
Well, you do have a point there. It does have to be cleaned anyways when he gets the new chip program. If it were me, I would schedule a cleaning ever couple of years. I would clean it now but not bother with the adjustments till I get my new program
Racer
Joined: Nov 2010
Posts: 460
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From: Oliphant Ontario
100% in agreement this time!! 
Tough to diagnose things from a description and almost as tough to fix using only a description.
In this case the right answer is "all of the above". He needs a tune for the new cam no mater what, and before he decides if that tune needs changes etc, he needs to verify everything on the car is running 100% right and adjusted to spec..
Tough to diagnose things from a description and almost as tough to fix using only a description.
In this case the right answer is "all of the above". He needs a tune for the new cam no mater what, and before he decides if that tune needs changes etc, he needs to verify everything on the car is running 100% right and adjusted to spec..
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A stock tune cannot be expected to run a modified engine like this one.
Oh sure it will run, but with many different problems and reduced power.
