Weird startup issue
February 18th, 2016, 7:39 PM
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Weird startup issue
So, my dad's truck has been having weird hard start issues for a good while now. It's been in a heated garage for the Winter so it's not really a cold start, but I'll get to the point.
When trying to start up the engine, it will keep cranking unless I give it some gas, but here's where it gets tricky:
If I give the throttle juuuust enough to sputter alive, it will continue to run at a very very low idle and be a bit rough. If I tap and release the gas too quickly it will die out. It will continue to do this if I repeat this process after it dies.
If I attempt to start the engine while giving it I'd say at least 25% of throttle, it will come alive and the RPMs will initially start high, and then the electronics will kick in and settle it down to a normal range. If I turn it off and start it back up again, I no longer need to give it throttle and the engine will still continue to run at normal speed.
I've already went through testing the electronics. The MAP, TPS, EGR, and vacuum lines were checked OK. The throttle body is clean as a whistle. As far the IAC, it seemed to be pretty gunked up and never been replaced, so I just replaced it. The voltages and pintle appeared to be working normally.
The only thing I can really think of is the coolant sensor, but I didn't want to go through the trouble of dealing with the coolant unless I absolutely needed to, which why I'm here to get some opinions. I was trying to test the resistance in the sensor while it was still in the manifold, but couldn't get leverage to work with the pins. Darn snub noses.
As far as drive-ability, there really aren't any issues. I'm not seeing a CEL. Only time I saw a CEL was when I was messing around with the wiring during testing. The fuel pump was replaced recently. As far as my dad says, the issue has been before that.
It's a 1995 G30 1-ton 5.7L TBI. That's pretty much it in a nutshell. It runs like a champ once it's driving. Thoughts?
Thanks
When trying to start up the engine, it will keep cranking unless I give it some gas, but here's where it gets tricky:
If I give the throttle juuuust enough to sputter alive, it will continue to run at a very very low idle and be a bit rough. If I tap and release the gas too quickly it will die out. It will continue to do this if I repeat this process after it dies.
If I attempt to start the engine while giving it I'd say at least 25% of throttle, it will come alive and the RPMs will initially start high, and then the electronics will kick in and settle it down to a normal range. If I turn it off and start it back up again, I no longer need to give it throttle and the engine will still continue to run at normal speed.
I've already went through testing the electronics. The MAP, TPS, EGR, and vacuum lines were checked OK. The throttle body is clean as a whistle. As far the IAC, it seemed to be pretty gunked up and never been replaced, so I just replaced it. The voltages and pintle appeared to be working normally.
The only thing I can really think of is the coolant sensor, but I didn't want to go through the trouble of dealing with the coolant unless I absolutely needed to, which why I'm here to get some opinions. I was trying to test the resistance in the sensor while it was still in the manifold, but couldn't get leverage to work with the pins. Darn snub noses.
As far as drive-ability, there really aren't any issues. I'm not seeing a CEL. Only time I saw a CEL was when I was messing around with the wiring during testing. The fuel pump was replaced recently. As far as my dad says, the issue has been before that.
It's a 1995 G30 1-ton 5.7L TBI. That's pretty much it in a nutshell. It runs like a champ once it's driving. Thoughts?
Thanks
