need help with diagnostics
09-20-2009, 04:09 PM
#1
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need help with diagnostics
hello,
i posted before about working on a 91, 5.7 c-4. what ive done so far is change the fuel pump, fuel filter, o2 sensor, and the CTS sensor. ( owner also changed the MAP sensor and the TPS sensor) the car starts and runs great until it gets warmed up. absoulutly no codes come up any more but the car still cuts off when it gets hot! the only other clue is that right before it cuts off, it will start making a sucking noise that seems to come from the sensor under the throttle body( which also looks new). once this car starts the cutting off thing, it will start several more times but then will not start again for several hours!??
can anyone give any insight to this problem? im almost ready to give this guy his car back for no charge, because i cant fix it! is it possibly the ECM?
HELP!!!
i posted before about working on a 91, 5.7 c-4. what ive done so far is change the fuel pump, fuel filter, o2 sensor, and the CTS sensor. ( owner also changed the MAP sensor and the TPS sensor) the car starts and runs great until it gets warmed up. absoulutly no codes come up any more but the car still cuts off when it gets hot! the only other clue is that right before it cuts off, it will start making a sucking noise that seems to come from the sensor under the throttle body( which also looks new). once this car starts the cutting off thing, it will start several more times but then will not start again for several hours!??
can anyone give any insight to this problem? im almost ready to give this guy his car back for no charge, because i cant fix it! is it possibly the ECM?
HELP!!!
09-20-2009, 04:34 PM
#2
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hello,
i posted before about working on a 91, 5.7 c-4. what ive done so far is change the fuel pump, fuel filter, o2 sensor, and the CTS sensor. ( owner also changed the MAP sensor and the TPS sensor) the car starts and runs great until it gets warmed up. absoulutly no codes come up any more but the car still cuts off when it gets hot! the only other clue is that right before it cuts off, it will start making a sucking noise that seems to come from the sensor under the throttle body( which also looks new). once this car starts the cutting off thing, it will start several more times but then will not start again for several hours!??
can anyone give any insight to this problem? im almost ready to give this guy his car back for no charge, because i cant fix it! is it possibly the ECM?
HELP!!!
i posted before about working on a 91, 5.7 c-4. what ive done so far is change the fuel pump, fuel filter, o2 sensor, and the CTS sensor. ( owner also changed the MAP sensor and the TPS sensor) the car starts and runs great until it gets warmed up. absoulutly no codes come up any more but the car still cuts off when it gets hot! the only other clue is that right before it cuts off, it will start making a sucking noise that seems to come from the sensor under the throttle body( which also looks new). once this car starts the cutting off thing, it will start several more times but then will not start again for several hours!??
can anyone give any insight to this problem? im almost ready to give this guy his car back for no charge, because i cant fix it! is it possibly the ECM?
HELP!!!
If you haven´t done it, you might want to take off the TB and then the IAC, spray it with WD-40, let sit for 10-15 minutes.
Clean the TB off course while you´re there, and put it together again.
Putting power on it (the IAC motor) will shoot small parts out of it, so put it in a plastic bag before you attempt ot test it.
I just happened to read this info elsewhere on the forum, so it´s not my personal experience. Just passing it on.
09-20-2009, 07:05 PM
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Sensor under the TB is the IAC, idle air control.
If you haven´t done it, you might want to take off the TB and then the IAC, spray it with WD-40, let sit for 10-15 minutes.
Clean the TB off course while you´re there, and put it together again.
Putting power on it (the IAC motor) will shoot small parts out of it, so put it in a plastic bag before you attempt ot test it.
I just happened to read this info elsewhere on the forum, so it´s not my personal experience. Just passing it on.
If you haven´t done it, you might want to take off the TB and then the IAC, spray it with WD-40, let sit for 10-15 minutes.
Clean the TB off course while you´re there, and put it together again.
Putting power on it (the IAC motor) will shoot small parts out of it, so put it in a plastic bag before you attempt ot test it.
I just happened to read this info elsewhere on the forum, so it´s not my personal experience. Just passing it on.
09-20-2009, 07:21 PM
#4
Supporting Vendor
hello,
i posted before about working on a 91, 5.7 c-4. what ive done so far is change the fuel pump, fuel filter, o2 sensor, and the CTS sensor. ( owner also changed the MAP sensor and the TPS sensor) the car starts and runs great until it gets warmed up. absoulutly no codes come up any more but the car still cuts off when it gets hot! the only other clue is that right before it cuts off, it will start making a sucking noise that seems to come from the sensor under the throttle body( which also looks new). once this car starts the cutting off thing, it will start several more times but then will not start again for several hours!??
can anyone give any insight to this problem? im almost ready to give this guy his car back for no charge, because i cant fix it! is it possibly the ECM?
HELP!!!
i posted before about working on a 91, 5.7 c-4. what ive done so far is change the fuel pump, fuel filter, o2 sensor, and the CTS sensor. ( owner also changed the MAP sensor and the TPS sensor) the car starts and runs great until it gets warmed up. absoulutly no codes come up any more but the car still cuts off when it gets hot! the only other clue is that right before it cuts off, it will start making a sucking noise that seems to come from the sensor under the throttle body( which also looks new). once this car starts the cutting off thing, it will start several more times but then will not start again for several hours!??
can anyone give any insight to this problem? im almost ready to give this guy his car back for no charge, because i cant fix it! is it possibly the ECM?
HELP!!!
09-21-2009, 04:16 PM
#5
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gonna try that today, thanks!
09-22-2009, 04:35 PM
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ohmed out all the injectors. found 6 of them under 8 ohms, 1 is 2.6 ohms. only one is above 10 ohms, which the manual states is the lowest reading acceptable. guess ive found my problem. it also explains why it runs fine when its cold, because it is still in "open" loop. thanks for the tip, Im gonna replace them tommorrow