Hey there. 1997 Grand Cherokee 5.2 will start only if I hold gas pedal down. The second I let off it shuts off. I let it warm up and the exhaust around the converter was crackling like it was very hot. It sounded like crinkling cellophane paper. Does this sound like a clogged catalytic converter to you folks? I just had a bad alternator and changed that out and my volts are now fine on the gauge. My interior lights are staying on for some reason as well. I just put in a brand new headlight switch and that did nothing besides cost me another $125 bucks. I was gonna replace the CPS but it is almost impossible on a V-8 and I was told at the auto parts place to always replace the throttle position sensor first since it does start and run if I hold the gas. I am just thinking that it may be the converter being clogged.. Any help would be great. Take care.

 

don't think it is, but one way to findout. Take the o2 sensor out of the exhaust, the one BETWEEN the motor and cat, NOT the one after. start it up and see what happens, if it runs better,then its a cat, if it runs the same, then its not. Is it throwing any codes?

 

No, it's not throwing any codes at all. I just replaced the throttle position sensor last night. It seems to run a bit better but it will still stall out if I hold it at say 2,000 rpm's and then suddenly let my foot off the gas. Even if it does not stall, the rpm's drop to almost nothing and it comes very close to stalling. In the last month, I have done the plugs, wires, air filter, alternator, throttle position sensor. Could it possibly be the MAP sensor or even the coil? I have never changed the coil in this vehicle. Thanks for the help.

 

Totally guessing here as i dont have much experience with the 5.2's..

Does it have an IAC? I'd remove it and try cleaning.

You have spark, it's running. The coil is working.

Tap the cat.. hear anything loose and rattling inside? Does it glow red when hot?

 

Last night I brought it out and let it run while it was dark outside to see if the cat or manifolds would glow but they did not, so I am of the thinking that the converter is fine. I will take a peek at the Idle Air Control Valve like you said.

Just a question......do you think the straight six Cherokee is a better vehicle (as far as servicing at home / dependable) than the V-8? I have had pretty good luck with this vehicle but my brother's have the 4.0 and they love them. Do they use the same transmissions? I have been told by a few people that the V-8 tranny is way more apt to give trouble than the 4.0 vehicle. I was told that by the clerk at the parts store so I don't know if it is correct or just something he had heard and was repeating. Thanks for the help.

 

mine used to do that to, and i replaced the converter cause it was a anoying peice of junk, and i havent had any problems yet, i thought it was an idle problem but the converter could of been the problem

 

have a 5.2 with 215k on it. Great motor. I would pull out the IAC and clean it good and put it back in. If a hunk of carbon got stuck in the pintle it would cause it to shut off.