Hey Everyone,
I've been lurking/learning from y'all for a bit now, but hoping I might get some more targeted help in case there's an 'if A and B, then for sure C' that I'm missing.
Bought my TJ just over a year ago (with a fair few 1 beer problems with it), but what keeps plaguing me is a rough idle and lean condition. It seems like every time I find a faulty component and replace it things get perfect for a brief magical moment and then an hour or a day later it gets back to the same old shenanigans.
Things I've done (I've chased and solved other issues along the way):
-Replaced sparkplugs with the recommended brand/model from these forums
-Tightened the ever loosening exhaust manifold to downpipe bolts when they started hissing
-Took pictures of the downpipe cat honeycombs, seemed fine
-Replaced the o2 sensor on bank 1 (Once was a bad guess didn't change anything, the 2nd time was indeed why my trims went haywire that week)
-Cleaned and tightened battery cables, and engine bay fuse box connections
-Cleaned the IAC and throttle body (Both the spray in place and remove and spray methods, separate occasions)
-Replaced all fuel injectors (Saw one leak a bit when I rotated it)
-Checked compression
-Checked resistance values from PCM to fuel injectors and all sensors on the intake
-Checked resistance and voltage differentials on various parts of the frame and engine looking for bad grounds
-Pulled off grounds and cleaned em anyways
-Replaced the rotten rubber boots on the intake manifold with silicone tubing
-Smoked the intake with a cigar, also played the tubing to the ear all over game listening for hissing
-Stuck a vacuum in the tailpipe on blow, and listened all the way up the exhaust for leaks
-Got fed up, took it to a mechanic, they said cylinder 6 had a wet sparkplug, felt like an idiot for missing the obvious, replaced the coil pack
-Checked purge valve with a vacuum gauge, also blocked off the main vacuum ports and checked to see if trims were affected
Symptoms:
-Rough Idle, sounds like it's missing intermittently and very slight surging sometimes
-Loss of power and runs like crap on accel from a stop every so often
-The 'OBDII Module Voltage' on the OBDII scanner is showing lower than the actual voltage measured on the battery... Like, battery would read 14.2 at idle, scanner would say 13.1-13.6 fluctuating all the time. Can't find this anywhere to see if it's normal.
-Bank 1 LTFT +9-11%, Bank 2 LTFT +7-9% (After injectors and o2 sensor and coil pack these were +3 and +0 for a bit)
-Will randomly die from idle while I have it in park for 5-10 minutes. Like, looking at OBDII data with it running in driveway, the engine will just cut off. No warning, no noises, no sputter, nothing. Doesn't even have the little sigh the engine gives when you turn the ignition off. And sometimes this resets the radio and LTFTs, like the battery was unplugged
-Getting slightly alarming engine sounds at red lights every so often... engine gets louder, sounds like it wants to die, your basic 'running like crap' sound...
-Engine tick at idle, used to go away once warm, now it doesn't, but it's an old Jeep, soooo
-Air wooshing noise on acceleration, didn't used to be there
Every single symptom except the fuel trims and the air noise on accel is intermittent, the rough idle is intermittently not as bad, more better when cold, more worse when warm.
No codes come up pending or confirmed, and looking at the graphs of data points when it dies, they just abruptly stop. Like, rpms report 700 and then there is no more data, and no sensor data I can see goes haywire right before.
Anyways, I'm leaning towards the IAC valve as a culprit even though it's been cleaned? Except for the PCM resetting on stall, which points to electrical? Could a bad IAC cause a power surge to shut off the PCM? Seems to me like it would just throw a code if the IAC motor shorted out...
Any help or direction to avoid replacing everything as budget allows and watching the jeep continue to sit in the driveway undriven would be greatly appreciated.
I've been lurking/learning from y'all for a bit now, but hoping I might get some more targeted help in case there's an 'if A and B, then for sure C' that I'm missing.
Bought my TJ just over a year ago (with a fair few 1 beer problems with it), but what keeps plaguing me is a rough idle and lean condition. It seems like every time I find a faulty component and replace it things get perfect for a brief magical moment and then an hour or a day later it gets back to the same old shenanigans.
Things I've done (I've chased and solved other issues along the way):
-Replaced sparkplugs with the recommended brand/model from these forums
-Tightened the ever loosening exhaust manifold to downpipe bolts when they started hissing
-Took pictures of the downpipe cat honeycombs, seemed fine
-Replaced the o2 sensor on bank 1 (Once was a bad guess didn't change anything, the 2nd time was indeed why my trims went haywire that week)
-Cleaned and tightened battery cables, and engine bay fuse box connections
-Cleaned the IAC and throttle body (Both the spray in place and remove and spray methods, separate occasions)
-Replaced all fuel injectors (Saw one leak a bit when I rotated it)
-Checked compression
-Checked resistance values from PCM to fuel injectors and all sensors on the intake
-Checked resistance and voltage differentials on various parts of the frame and engine looking for bad grounds
-Pulled off grounds and cleaned em anyways
-Replaced the rotten rubber boots on the intake manifold with silicone tubing
-Smoked the intake with a cigar, also played the tubing to the ear all over game listening for hissing
-Stuck a vacuum in the tailpipe on blow, and listened all the way up the exhaust for leaks
-Got fed up, took it to a mechanic, they said cylinder 6 had a wet sparkplug, felt like an idiot for missing the obvious, replaced the coil pack
-Checked purge valve with a vacuum gauge, also blocked off the main vacuum ports and checked to see if trims were affected
Symptoms:
-Rough Idle, sounds like it's missing intermittently and very slight surging sometimes
-Loss of power and runs like crap on accel from a stop every so often
-The 'OBDII Module Voltage' on the OBDII scanner is showing lower than the actual voltage measured on the battery... Like, battery would read 14.2 at idle, scanner would say 13.1-13.6 fluctuating all the time. Can't find this anywhere to see if it's normal.
-Bank 1 LTFT +9-11%, Bank 2 LTFT +7-9% (After injectors and o2 sensor and coil pack these were +3 and +0 for a bit)
-Will randomly die from idle while I have it in park for 5-10 minutes. Like, looking at OBDII data with it running in driveway, the engine will just cut off. No warning, no noises, no sputter, nothing. Doesn't even have the little sigh the engine gives when you turn the ignition off. And sometimes this resets the radio and LTFTs, like the battery was unplugged
-Getting slightly alarming engine sounds at red lights every so often... engine gets louder, sounds like it wants to die, your basic 'running like crap' sound...
-Engine tick at idle, used to go away once warm, now it doesn't, but it's an old Jeep, soooo
-Air wooshing noise on acceleration, didn't used to be there
Every single symptom except the fuel trims and the air noise on accel is intermittent, the rough idle is intermittently not as bad, more better when cold, more worse when warm.
No codes come up pending or confirmed, and looking at the graphs of data points when it dies, they just abruptly stop. Like, rpms report 700 and then there is no more data, and no sensor data I can see goes haywire right before.
Anyways, I'm leaning towards the IAC valve as a culprit even though it's been cleaned? Except for the PCM resetting on stall, which points to electrical? Could a bad IAC cause a power surge to shut off the PCM? Seems to me like it would just throw a code if the IAC motor shorted out...
Any help or direction to avoid replacing everything as budget allows and watching the jeep continue to sit in the driveway undriven would be greatly appreciated.
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