JustinJ94FSB
Newbie
Firstly, i viewed the threads that came up as suggestions when naming this thread. They did not provide any answers for my issue.
Secondly, To avoid a massive wall of TLDR text, my previous post that i edited the title to say *Solved* provides backstory on things ive done prior when solving other problems.
basically i replaced intake gasket, and some "while im in here" stuff. nearly everything GM genuine or delco original equipment. The low idle, stalling, stinky exhaust solved with new gm genuine EGR. i thought she was fixed!
--New Problem:
After getting new egr in, truck started, idled, and runs/drives absolutely perfect. Finally! I took it out for a drive. Maybe 150 miles round trip. It performed perfect the entire time (idle, driving, etc) After a hour or 2 i took a pit stop at a store to pee/get a drink. I come back out and start the truck and it fires up basically immediately. kind of just thinking, huh that was fast. As im sitting there looking at google maps determining which way i want to drive to go back towards home, the idle decides to go higher and higher up to about 1200-1500 on the factory tach. Im like what the heck? so i shut it off, and restart it and it sounds a little odd when it starts, and goes back to high idle. So i shut it back off. About 10 seconds later i start it back up and it idles perfectly normal. I tap the gas, it revs normal and drops back like it should and idles perfectly around 650ish. I decide to start driving towards home incase im going to have a problem. It drives perfectly fine all the way home, at least 50 miles with coming to intersections and stop lights , on and off of highways etc. I get home and park outside my house and it is idling perfect. I shut it off. Just for the hell of it, after about 20 seconds, i start it back up and it idles normal but within about 5 seconds it decides to just shoot up to 1200-1500 idle and i wait to see if it will change but it doesnt. So i turn the engine off, i wait 10 seconds and start it back up and it is idling perfect again around 650. It does this for like almost 10 minutes and i give up, shut it down, and call it a night. I Started it up today and drove it into town to get gas and it started, idled, and ran/drove flawless all the way to town. When the tank is full, and gas cap back on, i start the truck and it immediately goes up to 1500ish and idles there. I shut it off, wait 5 seconds start it up again and same thing. So i put it in drive and it drops to probably 750-900, put it in neutral and it goes back to 1500. I put back in drive, roll out of the parking lot under its current idle power, and baby it to the next intersection, i put it in neutral while sitting at the light and its idling normal again.
i cannot seem to pinpoint any rhyme or reason to it. It sometimes wants to shoot up to high idle and just sit there forever, or sometimes it idles fine forever. its sporadic behavior, does not currently seem to be related to open or closed loop but i think the highest idle speeds it reached were when it was full temp. i will try to start it again one of these mornings and let it idle up to operating temp to see if it does it during that process.
I've poked/wiggled various wires and ground straps (the one from ECT to thermostat housing, the braided ground straps from engine to frame, even the connector to the ECM, the column mounted ignition switch, and others. Ive attached a vinyl tube to a propane bottle with a valve, and ive opened it and ran the tube all over the place trying to see if i can find vacuum leaks. ive actually checked for vacuum leaks probably 10 times now since ive been fixing things on this truck since doing the intake gaskets. Ive never once found a vacuum leak on this truck and with every intake related gasket replaced it makes sense. All of the hoses (pcv, map, evap, egr, etc) I have a feeling it is electrical either a bad ground somewhere thats changing with heat and becoming weak, or a sensor that is diagnosing fine but isnt actually working, or maybe the IAC passage is dirty and my new IAC sometimes the pintle cant reach closed position? i have no idea.
send help! lol
Secondly, To avoid a massive wall of TLDR text, my previous post that i edited the title to say *Solved* provides backstory on things ive done prior when solving other problems.
basically i replaced intake gasket, and some "while im in here" stuff. nearly everything GM genuine or delco original equipment. The low idle, stalling, stinky exhaust solved with new gm genuine EGR. i thought she was fixed!
--New Problem:
After getting new egr in, truck started, idled, and runs/drives absolutely perfect. Finally! I took it out for a drive. Maybe 150 miles round trip. It performed perfect the entire time (idle, driving, etc) After a hour or 2 i took a pit stop at a store to pee/get a drink. I come back out and start the truck and it fires up basically immediately. kind of just thinking, huh that was fast. As im sitting there looking at google maps determining which way i want to drive to go back towards home, the idle decides to go higher and higher up to about 1200-1500 on the factory tach. Im like what the heck? so i shut it off, and restart it and it sounds a little odd when it starts, and goes back to high idle. So i shut it back off. About 10 seconds later i start it back up and it idles perfectly normal. I tap the gas, it revs normal and drops back like it should and idles perfectly around 650ish. I decide to start driving towards home incase im going to have a problem. It drives perfectly fine all the way home, at least 50 miles with coming to intersections and stop lights , on and off of highways etc. I get home and park outside my house and it is idling perfect. I shut it off. Just for the hell of it, after about 20 seconds, i start it back up and it idles normal but within about 5 seconds it decides to just shoot up to 1200-1500 idle and i wait to see if it will change but it doesnt. So i turn the engine off, i wait 10 seconds and start it back up and it is idling perfect again around 650. It does this for like almost 10 minutes and i give up, shut it down, and call it a night. I Started it up today and drove it into town to get gas and it started, idled, and ran/drove flawless all the way to town. When the tank is full, and gas cap back on, i start the truck and it immediately goes up to 1500ish and idles there. I shut it off, wait 5 seconds start it up again and same thing. So i put it in drive and it drops to probably 750-900, put it in neutral and it goes back to 1500. I put back in drive, roll out of the parking lot under its current idle power, and baby it to the next intersection, i put it in neutral while sitting at the light and its idling normal again.
i cannot seem to pinpoint any rhyme or reason to it. It sometimes wants to shoot up to high idle and just sit there forever, or sometimes it idles fine forever. its sporadic behavior, does not currently seem to be related to open or closed loop but i think the highest idle speeds it reached were when it was full temp. i will try to start it again one of these mornings and let it idle up to operating temp to see if it does it during that process.
I've poked/wiggled various wires and ground straps (the one from ECT to thermostat housing, the braided ground straps from engine to frame, even the connector to the ECM, the column mounted ignition switch, and others. Ive attached a vinyl tube to a propane bottle with a valve, and ive opened it and ran the tube all over the place trying to see if i can find vacuum leaks. ive actually checked for vacuum leaks probably 10 times now since ive been fixing things on this truck since doing the intake gaskets. Ive never once found a vacuum leak on this truck and with every intake related gasket replaced it makes sense. All of the hoses (pcv, map, evap, egr, etc) I have a feeling it is electrical either a bad ground somewhere thats changing with heat and becoming weak, or a sensor that is diagnosing fine but isnt actually working, or maybe the IAC passage is dirty and my new IAC sometimes the pintle cant reach closed position? i have no idea.
send help! lol