Bigbillyboy
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- Aug 22, 2024
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Ok. I have a 2005 liberty sport with the 3.7. Got it cheap from the po, because he didn’t use it and was tired of paying a shop to chase this issue. It was clean and straight, so I thought “what the hell”. I have read about 1000 different threads here and elsewhere.
What happens is: jeep starts easily. Runs like a champ, shifts perfectly, idles between 600 and 850, until it dies. RPM just drops then dies at idle, unless you’re driving. Then it has an abrupt miss, and will stumble along until it runs perfectly again. Sometimes it goes days in between happening, sometimes it happens once, sometimes I fight it all day. Rpm, throttle position and load don’t seem to make any difference. It happens at all of them.
When I picked it up, the previous shop had changed everything except the MAP sensor. Including the PCM. It’s obvious because they were all new.
I drove it and experienced this, at first no codes, but then p300 and TPS code. Following the advice of the forum, I replaced tps with with mopar. Drove again, very well, felt a couple of misses, no code. Let it idle and after a few min it just died. This time cam position sensor. Replaced with Mopar. Also replaced crank position sensor with mopar. Problem continued. No change. P300 code and tps code
This time I pulled throttle body and cleaned it. IAC was new, bench tested it and it worked.
QUESTION 1- should the IAC seal completely when closed. I can still get some air flowing through it by blowing or sucking through it. Not a mopar part.
While I was cleaning throttle body, I cleaned and rechecked all grounds. They seemed good. I also replaced an old battery. Checked fuel pressure, stable at 55-57 idle or under a load, and virtually no bleed off with key off. While waiting for new coils and plugs (OEM), I drove around with the scanner plugged in and watched live data. All sensors seemed to be working as normal with no observed irregularities when it would stall or stutter. Checked for vacuum leaks. None discovered. Installed new OE coils and properly gapped plugs. Replaced ASD relay at this time and checked for circuit continuity from sensors to PCM. All good. Wiggled every conceivable connector, wire, and ground with no affect. Cleaned MAP sensor even though it seems to read correctly and never had map sensor code.
Symptoms described above persist. Most of the time no code, but sometime TPS or camshaft error occur with the p300 code.
Drove around with scanner attached and noticed no abnormalities. Never had an O2 code.
QUESTION #2- Can a map sensor fail but not throw a code or read noticeable off?
I’m stumped. I like the little jeep and have time to mess around with it, but I’m not sure what to do next.
Any suggestions appreciated.
Jason
What happens is: jeep starts easily. Runs like a champ, shifts perfectly, idles between 600 and 850, until it dies. RPM just drops then dies at idle, unless you’re driving. Then it has an abrupt miss, and will stumble along until it runs perfectly again. Sometimes it goes days in between happening, sometimes it happens once, sometimes I fight it all day. Rpm, throttle position and load don’t seem to make any difference. It happens at all of them.
When I picked it up, the previous shop had changed everything except the MAP sensor. Including the PCM. It’s obvious because they were all new.
I drove it and experienced this, at first no codes, but then p300 and TPS code. Following the advice of the forum, I replaced tps with with mopar. Drove again, very well, felt a couple of misses, no code. Let it idle and after a few min it just died. This time cam position sensor. Replaced with Mopar. Also replaced crank position sensor with mopar. Problem continued. No change. P300 code and tps code
This time I pulled throttle body and cleaned it. IAC was new, bench tested it and it worked.
QUESTION 1- should the IAC seal completely when closed. I can still get some air flowing through it by blowing or sucking through it. Not a mopar part.
While I was cleaning throttle body, I cleaned and rechecked all grounds. They seemed good. I also replaced an old battery. Checked fuel pressure, stable at 55-57 idle or under a load, and virtually no bleed off with key off. While waiting for new coils and plugs (OEM), I drove around with the scanner plugged in and watched live data. All sensors seemed to be working as normal with no observed irregularities when it would stall or stutter. Checked for vacuum leaks. None discovered. Installed new OE coils and properly gapped plugs. Replaced ASD relay at this time and checked for circuit continuity from sensors to PCM. All good. Wiggled every conceivable connector, wire, and ground with no affect. Cleaned MAP sensor even though it seems to read correctly and never had map sensor code.
Symptoms described above persist. Most of the time no code, but sometime TPS or camshaft error occur with the p300 code.
Drove around with scanner attached and noticed no abnormalities. Never had an O2 code.
QUESTION #2- Can a map sensor fail but not throw a code or read noticeable off?
I’m stumped. I like the little jeep and have time to mess around with it, but I’m not sure what to do next.
Any suggestions appreciated.
Jason
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