1997 Cherokee Sport 4.0 L6 Automatic 166k
Gets worse the longer I drive....Cuts out while accelerating, backfires, the more I push the pedal the more it backfires and RPMs drop...After it drops, it surges back up and immediately drops back down...Gets so bad that all I can do is idle until I shut it off and turn it back on, then it runs fine at first, then starts all over again...It's getting worse and worse.....Check engine light is on for a bad O2 sensor, downstream, thats new...The light was on before this started happening...I took the whole top end apart tonight and it's getting a valve job and I'm cleaning the intake....I don't have high hopes those will fix it but I'm shooting in the dark now......
I have REPLACED
Coolant temp Sensor
Fuel Pressure Regulator/Filter
Air intake temp sensor
Both O2 sensors
Idle Air Control Valve
Throttle Position Sensor
Fuel Pump (and relay)
Crankshaft Position Sensor
I have CLEANED
QD Electronics Cleaner on All sensor and computer plugs
Ignition switch contacts
I have POURED
Two bottles of seafoam down the brake booster vacuum hose into the intake
Fuel Injector cleaner in gas tank
108 Octane Boost in the gas tank
PREMIUM fuel last three tankfulls
I have CHECKED
Fuel pressure- 49 PSI at idle and under load accelerating (The ONLY time the motor didn't fall on it's face was when the fuel pressure gauge was hooked up..Weird, I thought....But that was when the problem was more intermittant than it is now so I considered it a coincidence.)
I have SMOKED
Three packs of cigarettes....Thats alot for someone who doesn't smoke.
I am at wits end as this has turned out to be the biggest piece of junk vehicle I have ever owned....I still love it though and want it fixed by the end of deer season so I can get out and hunt some birds!
Any advice appreciated. If it leads to a correct diagnosis, you win free beer.