tony83

jus like the title emplies... this thing will barely idle and wont rev past 1500rpm it backfires and misses and everything else. any ideas? btw its getting good fuel and spark.... thank you

grsmnky1

What is your fuel pressure? I would say tps but the backfireing is throwing me off a little. Also before you get too far what was the last 2 things you did to your jeep.

matthewfbastrop

i had the same problem on my 92 xj i was getting 13-ish psi and couldnt figure it out come to find out the hose inside the tank had come off. luckly on my year i didnt have to drop the tank and just pulled it out and re attached and ta-da im on my way!!

tony83

hey guys... its a stock jeep...
here is a list of things that have been replaced/checked since this started... fuel pressure-good, sparking on all six, new plugs and wires new coil, new distributor cap, six month old cps, wiring harness is firing all injectors, unplugged map sensor and it ran worse, checked tps it was saying .79v closed and 3.86 wide open, checked for vacuum leaks, both new water temp sensors, new air temp sensor, and local mechanic checked the timing chain and said it was good plus its not making noise (although it is running like it has jumped timing) i have turned the distributor both ways just to see what would happen and its not a tooth off (there was another guy working on it before i started)
sorry for the lengthy explanation any help will be greatly appreciated

and if you already read this in my previous post, sorry lol

honestly i cant remember the exact psi but i was looking at a haynes manual when i checked it

matthewfbastrop

39 psi was required before mine would start, anything less and no go!!!

freegdr

checked it for codes yet search key on key off codes reading

tony83

ill check it again tomorrow to be sure but the plugs are turnin black and i can smell un-burnt while its running

grsmnky1

Was it running good and suddenly it wasn't or are you trying to fix a PO's mess up? You said you were not the first to work on it. Also why so many new parts you didn't throw parts at it to fix it or was it that neglected?

grsmnky1

Check your codes as posted earlier. Sometimes a O2 sensor will give bad numbers to the computer, causing it to run rich and foul plugs but the numbers are not always far enough off to throw a code. But the backfiring is usually caused by timing. Has it ran well since the new CPS was installed? And have you checked your kps?

tony83

this truck isnt mine personally but a family members... the guy that worked on it through alot of parts at it.. and it did suddenly quit one day but after some tinkering i got it to run but just barely lol... the only code it has is 12 from what i understand it just means the pcm has lost power in the last 50 cycles.. which would be correct ive had the battery out

thanks again

tony83

kps? and yes it ran good for a couple months after the crankshaft position sensor

grsmnky1

There are 2 sensors that have the same first initials the Crankshaft position sensor and the Camshaft position sensor. So Cps and Kps are used. Sorry. Well if the same symptoms were cleared up by insatalling a crankshaft sensor and your having the same symptoms again test the sensor and be sure it didn't go bad again. Was it a OEM sensor from Jeep dealer or aftermarket?

tony83

when the crankshaft position sensor took a dump the symptoms where that it would just randomly shut down going down the road and then restart after a few minutes... which makes since because i heard that if the cumputer doesnt get a signal from the cps that it will cut fuel and spark through the asd...

also about that cam position sensor some one told me to check it they said it was lacated in the distributor. could it be called any thing else? no one seems to sell one for this year and model...

thanks guys