Hello all, I'm new here, having a wierd problem with the wifes 01 grand cherokee laredo 4.0 auto 2wd, right at 200k miles. I worked 25 years in ford service dept but we all know these beasts work differently. here is the problem.....she says that after driving and coming to a stop sometimes she steps on the gas and the car wont accellerate, its still running but wont go above an idle. It doesnt happen often, I have driven it several times and never felt it happen, she says it happens mostly from a stop, but it has happened while driving, started loosing power pushed on pedal and then it jerked and went on without a problem. She said she pulled into a parking spot and trying to pull forward a little would not go when pedal pushed, put it in reverse, same thing, then back into drive and it finally went as normal. When I checked it I found 2 vac lines off on intake and reinstalled them, idle returned to normal and the truck ran fine for a few days, today she drove 20 miles to town and thats when it did the parking lot thing described above, no ck eng light on and I ckd the fuel press today, right at 50 lbs. like I said this is very intermittent, I have not got it to do it for me, and I have driven the same route, its hard to get her to understand that I cant fix what is not happening, I'm going to try a fuel filter tomorrow, just cause I have not repl it in a while, and to see whats in it. If anyone has heard of this before let me know, cause I cant figure this out, sorry for the long post but just trying to give as much info as possible, and my experience is on fords......BTW she has owned this jeep for 3 yrs and it has been very dependable, and I need to fix this so she feels safe in it......

 

Sometimes when a sensor starts to go it can act weird. I had a problem with my 04 going down the road it would just shudder and die. Usually start right up afterward, but it was a pain. I didn't get a check engine light either. I don't recall who but someone here suggested i check the TPS (throttle position sensor) it was cracked in half, don't know how it was even working at all. By no means am I an expert, but I think if you have 50 psi fuel pressure, I don't think that changing the fuel filter will fix the problem.

Hopefully Dave or someone with more experience will reply.

 

thanks Guardian, I had thought about that also, I ran into that on fords, there called in range failures, where they wont turn the ck eng light on but are causing the problem, and the tp is suspect just because of the symptoms. As for the fuel filter, I have not changed it about 30k and its a maintenence thing, and to see whats in it, just in case she picked up a bad load of fuel.....

 

The TPS would be my first suspect. Easy to check, cheap to change.

 

Welcome to CF!

Yeah Dennis, My 2000 4.0 has been flawless for 190K miles with no problems related to sensors, then like a switch, things started to malfunction. First it was my TPS, gave mostly the same symptoms. Then the CKPS started it's random stalling, anytime, anywhere for no reason. I changed that. When looking over my engine for loose vacuum hoses, I noticed 2 of my injectors were cracked. I put new Bosch 4-holers in it.

Now that it's cleared 200K, I'm waiting for the next shoe to drop!

I WILL say that these engines seem to work best with OE Mopar parts when it comes to sensors. As the saying goes, "Change with Mopar, change it ONCE!"

Just for your info, I'm a Chevy guy!

 

On my 04 in the recent past (last 8-10 months) I've changed the TPS & cam position sensor. Last week got a code for the crank position sensor. Picked up the Mopar part and the parts guy at the dealership said the pigtail is probably too short. If it is, trace it back to the harness and pull some slack. I'm like the part is expensive enough as it is, now your telling me they are scrimping on a few inches of copper wire.

 

Just to warn you, when changing the CKPS in my 2000 4.0, the sensor mounts on the driver's side, but the connector plug is on the passengers side. My wire looked short, but I compared it with the one I took out and it was the same length. Make sure it has the paper spacer on it to set the mounting distance right. That spacer gets torn off on startup. I found the easiest way to get to it is to take out the trans crossmember bolts and lower it down. It's still a PITA!

 

Good to know, thanks. I'll be changing it out on friday.