Weird TPS voltage issue, causing hanging idle
11-15-2013, 12:09 PM
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Weird TPS voltage issue, causing hanging idle My car started doing something weird, my TPS voltage with the engine off, key on, can be sitting at say .50. TPS % at 0. When I start the car the TPS voltage raises up enough for my TPS % to raise up to say 1 or 2 %. This causes a high idle of 1500 to 2000 RPM hang. It seem to only do it after the car has been ran for a while, to get hot, then if I shut it off and it sits for an hour to 45 minutes it will do this when I restart it. I changed the TPS but it did not help. I am beginning to suspect the alternator putting out too much voltage. When it does this my voltage gauge is higher then it normally runs at, say 16-17 volts. I have not verified with a DMM yet. The other thing is my head lights pulse sometimes, so I think I need an alternator anyway.
11-15-2013, 03:47 PM
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TPS should be fed a regulated +5V from the PCM.
You ought to look at this and see if it's drifting
with the IGN voltage but it "should" be stable.
What is the TPS voltage rising to? 0.50V is at the
low end of acceptable I think, lower might fault as
TPS voltage low. If the TPS +5V feed is stable and
TPS output is not, another possibility is a poor
ground connection (but that also ought to be PCM
returned). There are multiple grounds that are all
supposed to be electrically the same, but stuff
comes loose and crusts up, sometimes.
You ought to look at this and see if it's drifting
with the IGN voltage but it "should" be stable.
What is the TPS voltage rising to? 0.50V is at the
low end of acceptable I think, lower might fault as
TPS voltage low. If the TPS +5V feed is stable and
TPS output is not, another possibility is a poor
ground connection (but that also ought to be PCM
returned). There are multiple grounds that are all
supposed to be electrically the same, but stuff
comes loose and crusts up, sometimes.
11-15-2013, 03:48 PM
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TPS should be fed a regulated +5V from the PCM.
You ought to look at this and see if it's drifting
with the IGN voltage but it "should" be stable.
What is the TPS voltage rising to? 0.50V is at the
low end of acceptable I think, lower might fault as
TPS voltage low. If the TPS +5V feed is stable and
TPS output is not, another possibility is a poor
ground connection (but that also ought to be PCM
returned). There are multiple grounds that are all
supposed to be electrically the same, but stuff
comes loose and crusts up, sometimes.
You ought to look at this and see if it's drifting
with the IGN voltage but it "should" be stable.
What is the TPS voltage rising to? 0.50V is at the
low end of acceptable I think, lower might fault as
TPS voltage low. If the TPS +5V feed is stable and
TPS output is not, another possibility is a poor
ground connection (but that also ought to be PCM
returned). There are multiple grounds that are all
supposed to be electrically the same, but stuff
comes loose and crusts up, sometimes.
11-15-2013, 07:10 PM
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I went on and picked up an alternator today because I am pretty sure I need one, lights pulsing. The car only has 30K miles on it and everything is really clean. I am going to check everything tomorrow, go through all my grounds and do some testing. I knew the 5 volt, and ground went back to the PCM, but was thinking the higher voltage could be causing the 5 volt line from the PCM to come up with it.
Its been a while since I messed with it so I could not remember how much the voltage went up, on the TPS. My Red PCM connector is broke, so I wonder if that could be binding the connector. I have dielectric grease on the PCM pins as well.
I plan on doing some trouble shooting tomorrow.
Its been a while since I messed with it so I could not remember how much the voltage went up, on the TPS. My Red PCM connector is broke, so I wonder if that could be binding the connector. I have dielectric grease on the PCM pins as well.
I plan on doing some trouble shooting tomorrow.
11-17-2013, 06:25 PM
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Stuck the new alternator on, truck 145 amp alternator, looks like the plug with the single small red wire in it may have had some issues. It pulled apart when I tried to take the alt. out. I fixed that by adding some length to the wire and soldering everything up.
I also checked all my grounds by ohming them all out back to the battery and they were all good. Now the car is running a constant 14 volts at the battery. I tried several times to get the car to hang while logging and could not. Seems like I fixed it.
No more pulsing lights either..
I also checked all my grounds by ohming them all out back to the battery and they were all good. Now the car is running a constant 14 volts at the battery. I tried several times to get the car to hang while logging and could not. Seems like I fixed it.
No more pulsing lights either..
