Bloody Forhead ('94 ZJ 5.2L running rough)
My forhead is bloody from banging it against the wall. Any help is appreciated. I have a 94 Grand Cherokee, 5.2L all time 4wd. Starts & idles fine. Runs VERY rough above idle. Won't go over 20-30 mph & did I mention ROUGH. After it warms up for 15 min or so it will run just fine - plenty of power, smooth. Like something comes up to temp & decides to work properly. I've done the following with no luck. New plugs, wires, coil, cap & rotor. New MAP sensor. Removed & cleaned all injectors (soaked in B-12) new O rings. New fuel pump & filter. Fuel pres. in spec. Compression good. Run several cans of B-12 through it. Plugged Idle AIr Control valve - (all that did was make it idle poorly). I thought maybe it was stuck open. Can't find a vacuum leak. Codes are 14 - Map sensor voltage (has a new MAP sensor) 27 - injector control output drivers. All injectors seem to work. 54 - no camshaft position sensor signal from distributor. (can that be affected by operating temp?) What has me realy puzzled is that it will run fine after it warms up for 15 minutes or so (thoroughly warmed up). I've not changed the O2 sensor - yet - but I don't think that would have this much affect. Thanks for your time & help.
Originally Posted by bjf498 View Post
Originally Posted by ScottN3N View Post
Now the one thing that has me a bit cornfused is why would a bad TPS cause these problems in open loop and not closed? Input from the TPS is still used in closed loop "warm mode", but it's integrated with the feedback from the o2sensors at the same time. Headscratcher for sure. Since you've thrown every part at the whole thing but the temp sensor, TPS and o2 sensors and are likely to throw more parts at it, I'd still suggest a new TPS. At least, that's what I'd do. Take it for what it's worth.
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