Stalling RPMs

L

loner

New member
I can't find the problem and the mechanic is going nuts about this... It's a Grand Cherokee Laredo '98 4.0L 6c. Couple weeks ago the RPMs started to stall while you wait for the green lights, not too much but you can feel it, and not all the time. Recently the RPMs came so low that the engine stop while waiting in the light, I started it up again and It was ok. Last sunday, I was driving and the RPMs again came so low that it seems that the car shut off, pressing the gas a litlle further the car came alive again, and for the rest of the day was running good. It doesn't matter is the jeep is hot or cold, the stalling it's not constant, and not every day, adding to this, the fuel gauge come to empty, 3 o 4 time while driving and then back to where it was...
I went to the mechanic several times already, I made a tune up, change spark plugs, cables, fuel filter, air filter, distribution cap, etc... The mechanic drove the car and keep it running in the shop with the computers hooked up and nothing happend.
Any idea/suggestion will be very welcome...I'm running uot of options here...
Thank you.
Loner.
 

Yea! I had a 94 Cherokee do that to me. Get the throttle body clean and they also did some type of internal cleanout and pour some reagent to clean the whole system out.

Also you may want to check the catalytic converter. Is it shot?

Joey
 
I'm writing down every thing...Catalytic converted is fine... I think they did check the TPS, and the grade of gas is always the same since I got it, 87.
First thing tomorrow I'll take this ideas to the guys.
Thank you.
 

I look around in the past post and I found some ideas, puted on a list gave it to th guys, they checked them and tried the car again and keeps doing it.
Tomorrow they gonna replace the crank sensor and tps...
They told me that if the Catalityc were the problem the stalling will be constant and not once in a while...once the Cat. is broken is broken.
I'll keep you guys posted.
Thanks.
PS. if you have more suggestions please feel free to tell me.
 
Mechanic changed the crank sensor, and it's the same thing. Tomorrow he'll change the tps.
Nothing seems to work.
 
Is your mechanic not running the diagnostic test prior to replacing parts at your expense?, it sounds like he's guessing.. there are 2 other sensors that needs to be checked, IAC sensor and MAP sensor.. Start with the IAC Sensor..
 

Engines need 3 things: Fuel, air, spark. A spark problem with a missing plug, distributor, generator, etc, causes missing and sputtering, but not dropping RMs. If the engine is running smoothly but just ideling down and then peetering out, then it's air or fuel. Assuming that you're air cleaner isn't plugged with a bird's nest, I'd move on to fuel. Start cheap: 1)can o' injecter/carb cleaner 2) if you live where the temperature fluctuates frequently you may have some water/condensation in your fuel system so try HEET brand alcohol, which will dissolve the water 3)next is fuel filter 4) If your vehicle is old enough, the next thing is to just turn up the idle screw on the carberator as it may have loostened up and is just not getting enough fuel at idle 5)lastly is fuel pump, this one sucks because it may require removing the tank on your cherokee, I'm not sure. I would do all the cheap stuff first, though.
 
Here's the latest.... Today I'm changing the ignition coil, if this doesn't solve the problem, I'll drop the gas tank and replace the pump and the filter, wich in my model are lacated inside the tank. I't expensive...
Mechanic is convinced that is an electrical problem, since I'm not going to pay for the ignition coil...I made him a bet, if that doesn't work, he'll drop the tank and change the pump and the filter, if that solves the problem He'll pay it, If that doesn't solve the problem I'll pay for the work and both we'll be guessing wtf is going on...

I'll check the other 2 sensor again... the guys were checking pretty much everything, from the sensor to the conectors and the fuel pressure.
I'll keep you posted...
 
SteelHeadz said:
Is your mechanic not running the diagnostic test prior to replacing parts at your expense?, it sounds like he's guessing.. there are 2 other sensors that needs to be checked, IAC sensor and MAP sensor.. Start with the IAC Sensor..
Click to expand...

So far, I didn't pay anything, because they ran the test and can't find nothing, so they start guessing I guess, but they don't tell you that...anyway I know this guys for about 5 years, they work really really good, it's the first time they have this deadlock.
 

Ok... so far nothing worked. Yesterday they changed they spark wire plus cup, the car was running perfect until today in the morning that doesn't want to start. After several tries It started and you can smell the gas from somewhere, but not visible in the engine or any leakage...back to the shop, waiting fot the tow truck...
 
Found it!!!!... the problem was the computer itself, the mechanic told me to take the jeep to his friend whos's an electrician. My mechanic was convince that the problem was electrical, but he doesn't have all the right equipament to check the whole electrical system. Well, I took it there, they plug it and soon enough the jeep was doing the stalling again...
 
loner said:
Found it!!!!... the problem was the computer itself, the mechanic told me to take the jeep to his friend whos's an electrician. My mechanic was convince that the problem was electrical, but he doesn't have all the right equipament to check the whole electrical system. Well, I took it there, they plug it and soon enough the jeep was doing the stalling again...
Click to expand...
Does that mean it's Fixed?
 

you need to bring a new batterie because one of the cells are leaking ,i had the same issue , and after i changed the batterie out . the problem was gone and the rpms went back to normal, ,i put a optima batterie in and my vichle is working fine so before you start paying out money out of your pocket try this first and let me know .if you have any question's call me 940-4594-3449
james
 
Sorry I didn't read this one sooner but you already found the problem, mid to late 90's ZJ's have a weak spot in the ECM due to a small heat sink they put inside of it.
Several aftermarket ECM's (autozone, and pepboys) send the ECM out to be rebuilt and come with a bigger heat sink on the controller chip.
Its always the same problem not enough gas and tries to stall and completely shuts down till a 5 minute auto reset. When we first encountered it, it shut the ZJ down and we thought the fuel pressure relay, fuel pressure sensor or the fuel pump. It was the ECM.
 
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