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08-22-2013, 10:49 AM | #1 | |
AF Enthusiast
Join Date: Dec 2004
Location: Shellsburg, Iowa
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04 Liberty runs poor
I'm working on an '04 Liberty with the 3.7L engine. It runs extremely rough at idle, sometimes won't start without giving some throttle, occasionally needs flood-clear mode to fire. Once it starts it might die trying to rev it up, if it doesn't it will die as it comes back down to idle.
Fuel pressure is good. Compression is good. Has strong spark. Vacuum at idle is 5-10"hg with the needle vibrating between 5&10. Vacuum will hit 20" once revved up. Dropped exhaust at manifold to check if cats plugged (both upstream O2 sensors are rounded off). Runs better with exhaust off but no change in vacuum. Has no vacuum leaks, checked hot and cold with smoke machine, intake cleaner and propane, there are no leaks. All sensors are reading good, except MAP which agrees with both vacuum gauges I've tried. Had two codes for the downstream O2 sensors, both were for running rich. Spark plugs are new and already black. The injector pulse width is right around 10ms at idle (seems high to me but I can't find any reason the computer would be giving more fuel, unplugging the MAP sensor makes no difference) and falls to 5-7ms once it starts running fairly alright at above 1500 RPM. The customer was driving and it started running like this all of a sudden. It also had codes P030(2,4,5,6). CMP/CKP sync reads no while cranking but yes once running. The data updates slow on this one for some reason, I can't tell for sure if it is out of sync while cranking or if it's just not updating quickly enough. We tried replacing the fuel injectors because they were flushed at a big chain store less than a week before this started and bank 2 seemed to be losing slightly more pressure on flow tests. Injectors made no difference and the originals are back in it now. Anything else I should check before I start digging in to find the timing marks? The CMP sensor is on the bank that's registering most of the misfires, so I doubt that's it, but I'm out of ideas. Thanks for any help, Jason
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'04 Cavalier coupe M/T 2.2 Ecotec Supercharged 14 PSI boost, charge air cooler, 42# injectors Tuned with HP Tuners Poly engine/trans/control arm bushings Self built and self programmed progressive methanol injection system |
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