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TPS Problems

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Old Apr 5, 2015 | 04:55 PM
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1986 C4 L98...OK, so. the car wouldn't even start. it was just dumping fuel into the engine. I unplugged the TPS and it started up perfect. While it was running i plugged the TPS back in and it continued to run pretty good. I let the car warm up to operation temp and shut it down. I went to start it again and it wouldn't start again. So I unplugged the TPS again and it started up beautiful. Next day i went to start it and it wont run unless given constant pressure on the gas pedal. i didnt change anything, i just let it sit for a while. The TPS has been tested and is good. I'm so confused

Last edited by 86vett3; Apr 5, 2015 at 11:15 PM.
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Old Apr 6, 2015 | 12:18 AM
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Tested maybe but did you adjust it? It has to be adjusted to .54 volts to be right. Also how did you test it?

Unless its an open or shorted circuit its not doing to show up as bad always. Mine "tested" fine trying to do a linear test as pressed. But it was bad. Drove the car bonkers. Got worse as it got hotter.

After replacing the sensor which is dirt cheap anyways and adjusting it correctly it ran fine.
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Old Apr 6, 2015 | 05:15 AM
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It was adjusted to .54 volts with a voltmeter on the top 2 plugs in the sensor
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Old Apr 6, 2015 | 05:22 AM
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Id change the sensor especially if its old. Its cheap.
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Old Apr 6, 2015 | 05:25 AM
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This is the 3rd time I've changed it though and they have all read the same
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Old Apr 6, 2015 | 05:29 AM
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Do you have access to a scan tool? So you can see what the various sensors are actually showing?

Also Ive seen crazy things like this when the ground straps to the motor are loose.
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Old Apr 6, 2015 | 08:32 AM
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Originally Posted by 86vett3
It was adjusted to .54 volts with a voltmeter on the top 2 plugs in the sensor
Was it adjusted by loosening TPS and twisting it, or by using the minimum idle screw on other side of TB ?

Just curious if your blades are so closed that even the IAC can't supply enough air for start up.
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Old Apr 6, 2015 | 08:51 AM
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Lets test the TPS. Hook up a scanner and see what the ECM sees. It should be 0.54V and as you SLOWLY depress the pedal, it should go up bit by bit,

Also, I'd be curious as to what the ambient air tem is and the coolant temp is.
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Old Apr 6, 2015 | 11:35 AM
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My 91 was acting like that. It was really hard to start and had to hold the throttle half open. After it started it would start and run normally but if I let it set for a few hours it was hard to start again. Turned out to be the fuel pump. Its easy to check if you have a pressure gauge. May not be the problem but since you have changed the TPS it's worth a try.
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