K1500 Wont stay Running??
February 3rd, 2011, 9:41 PM
#11
Super Moderator
Professional Mechanic
Professional Mechanic
Do you have throttle body injection? If so 10 psi is ok but you do not have a MAF sensor. If you have CFI with a MAF sensor you do not have nearly enough fuel pressure.
February 4th, 2011, 11:19 PM
#14
CF Veteran
well, if it is as you said. you have to keep the throttle open to keep it running then I would say do a voltage test on the TPS and examine your Idle Air Solenoid. Look for a bad connection on the green wire going into the TPS connectors.
IAC may need to be cleaned or replaced.
IAC may need to be cleaned or replaced.
February 5th, 2011, 2:17 PM
#17
CF Veteran
I dont think so. A fuel filter that doesnt impinge on fuel pressure or stop the car from running? It only stalls when he lets off the pedal. Sounds like the problem is isolated to the throttle. If he holds it open it will stay running.
Options:
a. clogged, broken vacuum hose from TBI to MAP. From TBI to Vacuum Block. From Intake to brake booster.
-grab these hoses and check condition.
b. no reference signal on TPS. either signal loss from PCM or blocked connection at wire harness. or pinched reference wire. Loss of power(orange) and it wouldnt start. It could be getting ground from pinched somewhere but lack of reference signal means the PCM cant set the correct angle.
-back probe wires at TBI and slowly work the throttle linkage and look for voltage dropout(green and black). Disconnect and look for resistance between orange and black.
c. Idle solenoids could be carboned up so the rod is either too far out or stuck. Remove it, hit it with carb. cleaner and old toothbrush, clean off the mating plates on the carb. Try to get as much carbon as you can.
If you got fuel(13psi) and spark(it stays running for about 60 seconds) We exclude fuel filter and spark plugs. This has to be an A/F problem. Other sensors would give some code or running problem so we can clear out IAT, RPM, ECT sensors. Oil pressure sensor could turn the car off if pressure was too low. MAP too but lets not shotgun....unless it is too rich(ECT)-Do you have any color exhaust?
Here is what it sounds like to me. You start the car, the ISC holds the throttle open during cold start. After 60 seconds when the idle speeds drops the ISC should retract and the car should be controlled by the PCM actuating the TPS as needed. But this is the time when you stall. And when you restart it you can only keep it running IF you hold the throttle.
Options:
a. clogged, broken vacuum hose from TBI to MAP. From TBI to Vacuum Block. From Intake to brake booster.
-grab these hoses and check condition.
b. no reference signal on TPS. either signal loss from PCM or blocked connection at wire harness. or pinched reference wire. Loss of power(orange) and it wouldnt start. It could be getting ground from pinched somewhere but lack of reference signal means the PCM cant set the correct angle.
-back probe wires at TBI and slowly work the throttle linkage and look for voltage dropout(green and black). Disconnect and look for resistance between orange and black.
c. Idle solenoids could be carboned up so the rod is either too far out or stuck. Remove it, hit it with carb. cleaner and old toothbrush, clean off the mating plates on the carb. Try to get as much carbon as you can.
If you got fuel(13psi) and spark(it stays running for about 60 seconds) We exclude fuel filter and spark plugs. This has to be an A/F problem. Other sensors would give some code or running problem so we can clear out IAT, RPM, ECT sensors. Oil pressure sensor could turn the car off if pressure was too low. MAP too but lets not shotgun....unless it is too rich(ECT)-Do you have any color exhaust?
Here is what it sounds like to me. You start the car, the ISC holds the throttle open during cold start. After 60 seconds when the idle speeds drops the ISC should retract and the car should be controlled by the PCM actuating the TPS as needed. But this is the time when you stall. And when you restart it you can only keep it running IF you hold the throttle.
February 5th, 2011, 11:01 PM
#18
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Yes I did change the fuel filter and still did the same thing. It has to be electrical or air / Fuel. I'll go thru RacerX's recommendations one by one. I did notice the wire harness coming from the fir wall that eventually connects to the Throttle Control Sensor and the Idle control sensor passes over an air conditioning line that gets hot, that harness might be melted on the bottom. I'll run a volt meter thru it in the morning. I be back.!!??
February 6th, 2011, 6:57 PM
#19
CF Veteran
Now this another thing that GM does that Ford and the other makers dont do. They dont allow the car to start if the PCM is bad. Bad meaning no output. But GM computers are different. They have removable and replaceable PROMs. Now I dont have that information here but after you test all of this, you may have to backprobe at the PCM to see if you re getting a fuel signal leaving the PCM. Same as injector signal and other outputs.
Oh and I meant to say backprobe the TPS not the TBI.
Oh and I meant to say backprobe the TPS not the TBI.
February 7th, 2011, 3:51 PM
#20
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checking the voltage on those parts now...but one thing is the check engine light has never been on thru this whole issue..is there something to that? If everything checks out I guess its to a garage for a dianostic test to get the code.