stalling
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Joined: Jun 2011
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From: British Columbia, Canada
stalling
Alright, here is the problem, just started this afternoon, everytime I "blip" the throttle it stalls, if I let off slow it seems ok........I fixed my plenum, and it is a new tb (put a 50mm on), but I re-used the IAC.....cleaned battery terminals when I did the plenum about a month ago.
Tomorrow morning I am going to check the IAC, battery volts, fuel pressure and cat (I do suspect the cat is overdue because I was the 2nd one into the plenum) am I missing anything ?
Tomorrow morning I am going to check the IAC, battery volts, fuel pressure and cat (I do suspect the cat is overdue because I was the 2nd one into the plenum) am I missing anything ?
Administrator
Joined: Apr 2010
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From: Clayton MI
Did you disconnect the battery after swapping the TB? I would try just leaving the negative terminal off for about 20 minutes, start the truck up, let it re-learn the idle, and TPS base voltage, and take it from there.
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From: British Columbia, Canada
Yes, I had the battery dicsonnected for most of the day while I did it, and that was about 4 weeks ago, no problems until yesterday afternoon
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Joined: Jul 2007
Posts: 7,843
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From: DFW, Texas
It may be that the TB is not properly calibrated for the engine. What 50mm are you running?
If the set screw is too far out and the blades close too much, the iac can't compensate for it quickly enough and you stall.
Try this:
Start engine and remove brake booster hose. The engine will idle very high and the iac will shut completely, and the idle will go down a bit, but not all the way back down.
Turn off the truck.
Now reach back and unplug the iac.
Restart engine and slowly reconnect the brake booster hose. Does it stall out?
If yes, the plate is too far closed. Open plates to set idle at about 550-600rpms
If no, check current idle. Set the plate screw idle right around 550-600rpms.
Idle via the set screw only needs to be lower than the pcm set idle of about 650rpms, so that the pcm can control idle via the iac, but not so low as it cannot idle without it. When you are driving around at say 1/4 throttle, the iac is closed and air flow is controlled by the plates only, when you let off the gas the plates snap shut and the iac retracts to adjust idle.
A damaged or slow iac can be the culprit as well. If your idle without the iac plugged in checks out to 550-600rpms, suspect the iac and replace it.
If after you complete the above procedure, you notice while driving that your rpms drop too slowly after you let go of the pedal, close the plates just a bit more and reset the pcm.
If the set screw is too far out and the blades close too much, the iac can't compensate for it quickly enough and you stall.
Try this:
Start engine and remove brake booster hose. The engine will idle very high and the iac will shut completely, and the idle will go down a bit, but not all the way back down.
Turn off the truck.
Now reach back and unplug the iac.
Restart engine and slowly reconnect the brake booster hose. Does it stall out?
If yes, the plate is too far closed. Open plates to set idle at about 550-600rpms
If no, check current idle. Set the plate screw idle right around 550-600rpms.
Idle via the set screw only needs to be lower than the pcm set idle of about 650rpms, so that the pcm can control idle via the iac, but not so low as it cannot idle without it. When you are driving around at say 1/4 throttle, the iac is closed and air flow is controlled by the plates only, when you let off the gas the plates snap shut and the iac retracts to adjust idle.
A damaged or slow iac can be the culprit as well. If your idle without the iac plugged in checks out to 550-600rpms, suspect the iac and replace it.
If after you complete the above procedure, you notice while driving that your rpms drop too slowly after you let go of the pedal, close the plates just a bit more and reset the pcm.
Last edited by aim4squirrels; Jul 16, 2011 at 07:47 PM.
Thread Starter
|
Professional
Joined: Jun 2011
Posts: 184
Likes: 0
From: British Columbia, Canada
It may be that the TB is not properly calibrated for the engine. What 50mm are you running?
If the set screw is too far out and the blades close too much, the iac can't compensate for it quickly enough and you stall.
Try this:
Start engine and remove brake booster hose. The engine will idle very high and the iac will shut completely, and the idle will go down a bit, but not all the way back down.
Turn off the truck.
Now reach back and unplug the iac.
Restart engine and slowly reconnect the brake booster hose. Does it stall out?
If yes, the plate is too far closed. Open plates to set idle at about 550-600rpms
If no, check current idle. Set the plate screw idle right around 550-600rpms.
Idle via the set screw only needs to be lower than the pcm set idle of about 650rpms, so that the pcm can control idle via the iac, but not so low as it cannot idle without it. When you are driving around at say 1/4 throttle, the iac is closed and air flow is controlled by the plates only, when you let off the gas the plates snap shut and the iac retracts to adjust idle.
A damaged or slow iac can be the culprit as well. If your idle without the iac plugged in checks out to 550-600rpms, suspect the iac and replace it.
If after you complete the above procedure, you notice while driving that your rpms drop too slowly after you let go of the pedal, close the plates just a bit more and reset the pcm.
If the set screw is too far out and the blades close too much, the iac can't compensate for it quickly enough and you stall.
Try this:
Start engine and remove brake booster hose. The engine will idle very high and the iac will shut completely, and the idle will go down a bit, but not all the way back down.
Turn off the truck.
Now reach back and unplug the iac.
Restart engine and slowly reconnect the brake booster hose. Does it stall out?
If yes, the plate is too far closed. Open plates to set idle at about 550-600rpms
If no, check current idle. Set the plate screw idle right around 550-600rpms.
Idle via the set screw only needs to be lower than the pcm set idle of about 650rpms, so that the pcm can control idle via the iac, but not so low as it cannot idle without it. When you are driving around at say 1/4 throttle, the iac is closed and air flow is controlled by the plates only, when you let off the gas the plates snap shut and the iac retracts to adjust idle.
A damaged or slow iac can be the culprit as well. If your idle without the iac plugged in checks out to 550-600rpms, suspect the iac and replace it.
If after you complete the above procedure, you notice while driving that your rpms drop too slowly after you let go of the pedal, close the plates just a bit more and reset the pcm.
I will run through the checks today, thanks for the help!
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