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  #1  
Old 10th August 2008
texture texture is offline
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Default Engine stops when the gas pedal is released

So here's the story, I left my lights on a few times, battery died, so I figure time for a new one (after 9 years). On the way to the shop the engine completely shut off when I took my foot off the gas as I was exiting the free-way. Must be the battery I thought, got the new one installed and found the issue continuing to happen, however much worse now, now whenever the gas isn't pressed the engine comes to a halt. Stoplights, traffic, have all become a nightmare. After longer periods of down time the issue seems to subside for a while but shortly returns.

I have since the issue occurred, replaced the fuel filter, the air filter, and brought the oil level up, I even tried putting higher octane into the tank, all these things had noticeable effects on the performance, but the issue remains. Am I missing something? I can't imagine why it'd come out of nowhere like this! Thanks in advance you guys, this place has saved my butt many times!
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Old 10th August 2008
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c900 c900 is offline
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Quote:
Originally Posted by texture
So here's the story, I left my lights on a few times, battery died, so I figure time for a new one (after 9 years). On the way to the shop the engine completely shut off when I took my foot off the gas as I was exiting the free-way. Must be the battery I thought, got the new one installed and found the issue continuing to happen, however much worse now, now whenever the gas isn't pressed the engine comes to a halt. Stoplights, traffic, have all become a nightmare. After longer periods of down time the issue seems to subside for a while but shortly returns.

I have since the issue occurred, replaced the fuel filter, the air filter, and brought the oil level up, I even tried putting higher octane into the tank, all these things had noticeable effects on the performance, but the issue remains. Am I missing something? I can't imagine why it'd come out of nowhere like this! Thanks in advance you guys, this place has saved my butt many times!
If the car has a 16V engine, check that the two microswitches in the TPS (throttle position switch/sensor) are operating properly, and that at the 'no throttle' position, only one of the switches is giving an output. If the ECU sees that both the 'no throttle' and 'wide-open throttle' inputs are active at the same time it might not know what to do and shut off the fuel pump.

Also see what the AIC (automatic idle control) motor is doing. The ECU uses that to control engine idle at no-throttle.

If the car has an 8V engine, you might need to check that the airflow sensor plate is working correctly and that the throttle valve dashpot is ok.

Can you provide any other details about what you think the problem might be? Does it only occur when you let the throttle drop off quickly, or does it happen when you let it off slowly as well?

Craig.
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Old 10th August 2008
texture texture is offline
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Quote:
Originally Posted by c900
If the car has a 16V engine, check that the two microswitches in the TPS (throttle position switch/sensor) are operating properly, and that at the 'no throttle' position, only one of the switches is giving an output. If the ECU sees that both the 'no throttle' and 'wide-open throttle' inputs are active at the same time it might not know what to do and shut off the fuel pump.

Also see what the AIC (automatic idle control) motor is doing. The ECU uses that to control engine idle at no-throttle.

If the car has an 8V engine, you might need to check that the airflow sensor plate is working correctly and that the throttle valve dashpot is ok.

Can you provide any other details about what you think the problem might be? Does it only occur when you let the throttle drop off quickly, or does it happen when you let it off slowly as well?

Craig.

Thanks Craig! I try to be familiar with my car but just changing the fuel and air filter pushed some limits for me, is there anyway I can get you to explain the suggestions a little further? Where they are, what tools? Or just point me in the right direction!

As far as more details on my end it seems to happen intermittently now after changing all the filters and stuff, but it seems like instead of idling it just drops too far and stops. And happens just the same if I gradually release or suddenly release... Does that help? Thanks!

*edit* I'm pretty sure it's an 8V
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  #4  
Old 10th August 2008
16saabs 16saabs is offline
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sounds like a short?, but could be the throttle sensor as stated by craig,
Is your battery staying charged ok?? could be alternator shorting and will kill you dead but once stoped it lets you start up again.
check earth grounds for the car as well
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Old 10th August 2008
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Steve Corgan Steve Corgan is offline
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Texture,

Let's see, you said, "On the way to the shop the engine completely shut off when I took my foot off the gas as I was exiting the free-way." Do you mean it dies when left to itself at idle, but restarts and runs as long as you keep the rpms up? If that's the case it could be something as simple as a vacuum hose that was inadvertently knocked off it's connection. Pop the bonnet and start tracing / checking each hose. Not only look for a disconnected hose but also for cracks and leaks in the hoses.

My car would die at stop lights or any time let it alone at idle. I fixed a couple of vacuum hose leaks and sprayed throttle body cleaner into the AIC and throttle body. I lubricated the AIC with WD-40 after cleanning. Now my car idles perfectly all the time. I think there's instructions for cleanning the AIC in the FAQs in this forum.
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