cfrennier

ok i am new to the site and have been searchin on here for over a week on what my possible issue could be. i have a 1994 grand cherokee with a 318 in it and it just is not running right. i have replaced the coil,crank sensor, cam sensor, plugs, wires, cap n rotor, map sensor, i have even unhooked the O2 sensor, dun the egr bypass, taken the vaccuum line off the fuel pressure regulator and after all that still no change. there is also no converter onit. when it the motor is cold it will fire rite up n run perfect but as soon as it hits about 130 degrees it starts actin up n acts like it is gettin no fuel or spark. if u step on the gas it just dies but it will idle fine for like 10 mins then start runnin real rough n the die, it also starts real hard meening it will crank sumtimes for like 1-2 minutes b4 firing. i am at a total loss with this thing n hope i can get sum help please.

Bustedback

Could be the coolant temp sensor relaying wrong info to the PCM. If it is telling the PCM the engine is cold, it will run rich and run real crappy. A bad MAP sensor can cause issues too. You really need to hook a scan tool (not a code reader) up to the data link and take a look at the live data stream and see what is going on.

cfrennier

alright just replaced the coolant temp sensor and it seems a little better but now goin down the road if u flat foot it it pops n backfires n falls on its face

Bustedback

Sounds like it's starving for fuel. Replace the filter first (driver side above the rear axle) and see if there is any change. You should also check the fuel pressure, the spec is 44 to 55 psi.

cfrennier

could it be the computer as this only happens what the jeep reaches aroun 140 degrees now...it takes throttle fine up till then n idles very smooth

Bustedback

PCMs rarely fail, not saying they don't, but rarely.

Chevokeeman

Could be fuel pump going out or fuel filter plugged. Could go to Autozone or O'Reilly's and have the codes checked when it starts acting up. One guy had a bad air inlet temp senser out and it didn't show any codes. Chevokeeman.

amillett72

I have a 96 Jeep Grand Cherokee Laredo, I seem to be having a similar issue. It starts up fine, but if I need to stop at a light or idle at all I need to give it a little gas. If you try to step on it, it chokes. Replaced fuel filter and checked all hoses MAP sensor etc. Stumped any ideas?

Bustedback

You need to hook a scan tool up to the data link connector and take a look at the data stream, and also need to check the fuel pressure with a gauge hooked to the test port on the fuel rail. With the scan tool you need to do a TPS sweep, meaning you look at the TPS voltage and slowly step on the gas pedal and look for any dead spots or glitches in the voltage. A dead spot would cause the engine to stumble and would indicate a bad TPS.

cfrennier

ok i just put a new fuel pump n filter on it n it does the same thing runs fine wen cold then wont take the gas after warmed up....im stumped

jnicewan

Do you have the means to put a scanner on it and look at data? When you say it runs ok cold and starts acting up when warm it sounds like a fuel/air problem. When the engine is cold its running in "open loop" meaning its not looking at the oxegon sensors to compensate for fuel corrections and typically runs rich, as soon as the engine warms up some it enters "closed loop" and uses the oxegon sensors to compensate the air/fuel ratio for lean or rich conditions.

Your issue kind of sounds like a vacuum leak concern to me, vacuum leaks usually dont affect speed density systems while cold in open loop, except maybe a high or slightly higher than normal idle speed-maybe... When the engine enters closed loop the oxegon sensors will notice the vacuum leak/lean condition and start trying to compensate. check for vacuum leaks, hoses gaskets etc. Keep in mind the 5.2-5.9's are know to have intake gaskets leak or get sucked in internally or into the lifter valley, it can be hard to diagnose but thats a possibility. Vacuum leaks usually wont give you an accel problem at WOT but its possible.

cfrennier

ok just did oxygen sensor and air charge sensor n still the same prob

ct67_72

I was thinking the same before I read this. you need to have a scan tool on it with data. could very well be a vacuum leak. at this point you are going to get nowhere without a scanner though.

cfrennier

the only thing different that happens now is when i first start it i gotta play wit the throttle after it starts for about 15 seconds to keep it runnin the it idles fine

cfrennier

could this be a computer issue