TheDude Posted December 11, 2018 Share Posted December 11, 2018 A Cherokee. A 96' OBII Cherokee Country to be exact. 4.0, Auto, and Originally Rwd but now has a transfer case installed so I call it a 3/4 4wd. 222k on the Odometer but ran great up until recently aside from less than great gas mileage. Now when it's stone dead cold it barely starts and runs horribly rough until it warms up, say three minutes or so. And it even once it clears up the long term fuel trim is pegged -32.8 trying to pull it lean. No Check Engine Light, or stored codes. Fuel pressure stays at 50PSI during the rough idle. Using my scan tool the TPS shows 0.82 closed but I swapped in others and they read very close to one another. Installed a new one and reads the same. O2 is a new NGK heats up fast and switches between 0v-1.0v except for times it hangs high indicating it being an overly rich mix. MAP reads 29.8 Baro Has K Suspension four hole injectors. NGK plugs, NOS Mopar wires and newer cap/rotor. New fuel filter too. Today I put the new TPS and a spare Cam sensor in at lunch and it seems to not idle terrible and it shows the cam and crank signals being synced unlike before when cold now but I can't confirm until the morning when 100% cold to be absolutely sure. I reset all adaptive memory before starting it, But I left my scanner plugged in on the way home and it still reads -32.8 long-term fuel trim.. So what's left to cause a rich condition? Can an overly worn engine cause overly rich mix? Timing chain stretched? I believe the spark advance shows around 17 degrees. Thoughts? Ideas? Prayers? Thanks for reading! Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Green Mesa XJ Posted December 11, 2018 Share Posted December 11, 2018 1996 is a odd ball year, a lot of one off parts like fuel pump and sender. I forget what the pressure is supposed to be on those From what you’ve troubled shooter already my gut instinct is map sensor and fuel pressure regulator , leaking injectors 222k on a 4.0 is nothing to worry about, although before a lot of what you’ve done I’d check compression.Sent from my iPhone using Tapatalk Pro Link to comment Share on other sites More sharing options...
TheDude Posted December 11, 2018 Author Share Posted December 11, 2018 I'm well aware of the 96' being odd years. The injectors are new and the poor fuel mileage was pre-existing them so I doubt they're bad. Fuel pressure spec is 49.5 and their is no pressure regulator on this year. MAP is reading 28 - 29 Baro which is pretty perfect. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Green Mesa XJ Posted December 11, 2018 Share Posted December 11, 2018 Hum.How bad is gas mileage?Sent from my iPhone using Tapatalk Pro Link to comment Share on other sites More sharing options...
Green Mesa XJ Posted December 11, 2018 Share Posted December 11, 2018 Hum.How bad is gas mileage?Edit : I thought the regulator was in the fuse pump sender assembly ? Sent from my iPhone using Tapatalk Pro Sent from my iPhone using Tapatalk Pro Link to comment Share on other sites More sharing options...
Pete M Posted December 11, 2018 Share Posted December 11, 2018 does it have an EGR? Link to comment Share on other sites More sharing options...
TheDude Posted December 11, 2018 Author Share Posted December 11, 2018 does it have an EGR? 91 and up does not have an EGR. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Pete M Posted December 11, 2018 Share Posted December 11, 2018 well, then never mind that. Link to comment Share on other sites More sharing options...
Green Mesa XJ Posted December 11, 2018 Share Posted December 11, 2018 Going back to basics, how do we know the injectors are good?Ive seen them fail rarely and not bad enough to trigger codes on newer cars.Sent from my iPhone using Tapatalk Pro Link to comment Share on other sites More sharing options...
TheDude Posted December 11, 2018 Author Share Posted December 11, 2018 Going back to basics, how do we know the injectors are good?Ive seen them fail rarely and not bad enough to trigger codes on newer cars.Sent from my iPhone using Tapatalk Pro The running rich was an issue before I replaced them and they're remaned ones from K Suspension.Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Green Mesa XJ Posted December 11, 2018 Share Posted December 11, 2018 Are the temperature readings accurate or seem accurate? If we maybe believe the hardware is not faulty maybe the software is getting something erroneous like temperature and mixing the fuel wrong. Maybe the pcm is failing somewhere. I doubt a worn engine would cause running rich unless it wasn’t firing and if compression were that low it ought to throw a code. Beside I doubt that motor is all that bad off unless it was severely abused. In old HO xjs/MJs I’d suspect O2 sensor, and map. Older cars Mass air flow sensor. On the OBD2 xj I’m not sure. Sent from my iPhone using Tapatalk Pro Link to comment Share on other sites More sharing options...
Green Mesa XJ Posted December 11, 2018 Share Posted December 11, 2018 Could IAC do any of this? Sent from my iPhone using Tapatalk Pro Link to comment Share on other sites More sharing options...
TheDude Posted December 11, 2018 Author Share Posted December 11, 2018 Could IAC do any of this? Sent from my iPhone using Tapatalk Pro IAC only adds air and they're kind of impossible to test. Musni don't know if they would run rich because of it. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Green Mesa XJ Posted December 11, 2018 Share Posted December 11, 2018 Did 96 have air temperature readings?That or coolant temp are my half assed guess at why it’s rich at start upSent from my iPhone using Tapatalk Pro Link to comment Share on other sites More sharing options...
TheDude Posted December 11, 2018 Author Share Posted December 11, 2018 It's rich at all times. It has a coolant temp sensor and a intake temp sensor. They both read perfect whenever I check them. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
shelbyluvv Posted December 12, 2018 Share Posted December 12, 2018 Check your alternator and battery. Just battled similar symptoms on my daughter's 96 Link to comment Share on other sites More sharing options...
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