2011 Aveo won't idle after engine repalcement
January 31st, 2016, 7:01 PM
#21
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fuel trim is based primarily off of the front 02, some systems use the maf/map as redundancy or an in/out comparison.
fuel pressure and volume are ok? have you tried cleaning the MAF? the majority of the time the STFT is reading maxed out like that its either a vacuum leak or the pump not putting out like it should. when I get a little extra time i'll try to do some research I personally don't have much experience with the 1.6
fuel pressure and volume are ok? have you tried cleaning the MAF? the majority of the time the STFT is reading maxed out like that its either a vacuum leak or the pump not putting out like it should. when I get a little extra time i'll try to do some research I personally don't have much experience with the 1.6
February 23rd, 2016, 5:07 PM
#22
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Well... this car is still in my garage. I keep having to go out of town for a week at a time so progress has been slow to none and I'm about to use AAA to have it towed to the only local shop I'd trust.
It all seems to be tied to short term fuel trim. Above 3,000 it's totally* normal, below 3,000rpm it's pegged around +25. That asterisk is for a spike about every 12 seconds where the STFT spikes at high RPM for a single frame and then drop back into negativelow numbers.
Going over this in other forums someone said it sounded like the PCV diaphragm may have gone. While trying a series of things I plugged the PCV inlet in the throttle body and routed the PCV outlet directly into the MAF sensor (pulled out of the airbox) and that didn't help any but when I taped over the hose and cut a small slit in it, greatly restricting flow, that did help and the car seems to settle into a fairly normal idle.
I thought this was a Eureka moment so I got a new valve cover. In the meantime I drew suction on the hose on the OE valve cover by mouth and was able to feel and hear the diaphragm close. When I replaced the VC I drew a vacuum again and it acted just the same so I think the PCV diaphragm wasn't bad after all.
Replacing the VC did nothing to change the running of the engine. I don't know why it ran better that one time but I haven't been able to recreate it with the same "accessory hose"
No vacuum leaks, the snorkel is good, the PCV pipe is good, checked the intake and everything else with both smoke and MAPP gas for leaks, nada.
Any last ideas before I give up on this thing and send it down the road?
It all seems to be tied to short term fuel trim. Above 3,000 it's totally* normal, below 3,000rpm it's pegged around +25. That asterisk is for a spike about every 12 seconds where the STFT spikes at high RPM for a single frame and then drop back into negativelow numbers.
Going over this in other forums someone said it sounded like the PCV diaphragm may have gone. While trying a series of things I plugged the PCV inlet in the throttle body and routed the PCV outlet directly into the MAF sensor (pulled out of the airbox) and that didn't help any but when I taped over the hose and cut a small slit in it, greatly restricting flow, that did help and the car seems to settle into a fairly normal idle.
I thought this was a Eureka moment so I got a new valve cover. In the meantime I drew suction on the hose on the OE valve cover by mouth and was able to feel and hear the diaphragm close. When I replaced the VC I drew a vacuum again and it acted just the same so I think the PCV diaphragm wasn't bad after all.
Replacing the VC did nothing to change the running of the engine. I don't know why it ran better that one time but I haven't been able to recreate it with the same "accessory hose"
No vacuum leaks, the snorkel is good, the PCV pipe is good, checked the intake and everything else with both smoke and MAPP gas for leaks, nada.
Any last ideas before I give up on this thing and send it down the road?