PCM speeding up car by itself??????
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TECH Junkie
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From: From the Bowels of Hell!!! You want some of me bitch?!?!?!
PCM speeding up car by itself?????? When I let off the brake pedal and start to move,the motor suddenly picks up speed by itself. I can let it go and it will get to almost 20mph like that. Now I am running a TH400 and have had all the tranny codes deleted. When I come to a stop, the motor takes a second before it comes down to idle. Even if I put it in neutral and coast to a stop, same thing. I must be completely stopped before it will idle. Is there some sort of speed sensor that is causing it? Can that be adjusted via LS1 Edit?
Tim
Tim
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From: Lake Zurich, IL
Re: PCM speeding up car by itself?????? not sure if it's the same issue I was having... but after I put my 42lb injectors in (after I tuned PCM for them so the car would run) I was surging down low...
I would come to a stop and RPMs would go up to like 1500 then slowly come back down and either surge up and down (eventually dying) or sometimes it would actually hold the idle...
I corrected this by leaning the car out more (via IFR table, lower kpa values I set leaner than upper), also brought Main VE down to 55% original from 0 to 1200 RPM (used to be 70% original before injectors) ...
now when I come to a stop it drops perfectly to idle (900) and stays there... no more up and down hunting, dying , etc...
Another possibility... maybe you have a small vacuum leak? Letting in unmetered air takes PCM a little time to compenstate? LTRIMs look good?
I would come to a stop and RPMs would go up to like 1500 then slowly come back down and either surge up and down (eventually dying) or sometimes it would actually hold the idle...
I corrected this by leaning the car out more (via IFR table, lower kpa values I set leaner than upper), also brought Main VE down to 55% original from 0 to 1200 RPM (used to be 70% original before injectors) ...
now when I come to a stop it drops perfectly to idle (900) and stays there... no more up and down hunting, dying , etc...
Another possibility... maybe you have a small vacuum leak? Letting in unmetered air takes PCM a little time to compenstate? LTRIMs look good?
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From: From the Bowels of Hell!!! You want some of me bitch?!?!?!
Re: PCM speeding up car by itself?????? Have to check LTRIMS. The car idles good, no surging. It drops to idle only when I come to a complete stop. If I let off the brake, and roll maybe 10 feet, it picks up rpm suddenly, not on a gradual climb. I can put it in neutral and coast to a stop, but it still won't go to idle until I'm completely stopped. I would think a vacuum leak would cause it to run at a higher rpm even at idle position.
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TECH Junkie
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From: From the Bowels of Hell!!! You want some of me bitch?!?!?!
Re: PCM speeding up car by itself?????? Would the IAC thing make a difference if it was in gear only and NOT moving?
I don't have Edit. Thunder did the tuning, but I haven't been back for them to look a this yet. I want to try to get an idea of where to look when I do.
I don't have Edit. Thunder did the tuning, but I haven't been back for them to look a this yet. I want to try to get an idea of where to look when I do.
Staging Lane
Joined: Jan 2002
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From: Baton Rouge, La.
Re: PCM speeding up car by itself?????? Hi Tim, Maybe your brake booster is pulling too much vacuum while your car is rolling. When it is stopped it maybe has less load. Who knows? May also be a little person in there messing with it. LOL. Jimmy
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TECH Junkie
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From: From the Bowels of Hell!!! You want some of me bitch?!?!?!
Re: PCM speeding up car by itself?????? Well the car idles great, and its a very loos convertor. Cam is somewhat big, I'll check those settings out.
Re: PCM speeding up car by itself?????? There's something about the IAC not settling to
baseline until the car is fully stopped, to keep
the IAC loop from bottoming out & hunting. It sets
a higher value & drops it slowly to the setpoint
after you drop below (whatever speed threshold)?
baseline until the car is fully stopped, to keep
the IAC loop from bottoming out & hunting. It sets
a higher value & drops it slowly to the setpoint
after you drop below (whatever speed threshold)?
Re: PCM speeding up car by itself?????? Tim, it does sound like the RAF in Running air is too high.
Reduce RAF values at the temps at which it's doing it. Try -.50 and adjust up or down from there.
Reduce RAF values at the temps at which it's doing it. Try -.50 and adjust up or down from there.
