93 5.2 only starts when floored - won't idle

Greetings,

I have a 1993 Grand Cherokee Laredo with a 5.2 that will only start if the gas peddle is held to the floor. Once it is running it seem to go through the rpm's just fine but will not idle. If I keep steady on the gas it will sit at 1000 rpm just fine and run smooth. Lift my foot off the pedal and it dies.

I have a 1993 Grand Wagoneer with the same engine and it runs perfectly so I have been playing music parts. I have swapped out the MAS, TPS and IAC. All with no result.

Anyone have any ideas?

possibly a vacuum leak. sometimes the intake manifold plenum gasket will leak. there is a metal pan that bolts to the underside of the intake, and that gasket blows out. if there is oil getting into the air cleaner this could be the problem. even if you swapped out iac motors, the throttlebody plates can be gummed up and not let your engine get enough air at idle

X2 on the blown intake gasket.

Good Luck

Nick

This is not NAZJA.

veedubshafer said:

This is not NAZJA.

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Wow....real helpful. Congrats on helping someone in need.

Anyways, since you've swapped out all the main sensors with no luck in solving the problem, I too would lean towards a possible vacuum leak.

Not being familiar with the 5.2, as this forum deals with Cherokee's and Commanche's, you might search around on www.nagca.com ....they're a Grand Cherokee specific forum. I would also check out www.cherokeeforum.com ...there's information on both Cherokee's and Grand Cherokee's over there as well. You'd probably have better luck on either of those two sites.

Hey thanks for the suggestions! Sorry 'bout the posting in the wrong forum. Kind of funny to get flamed in a Jeep forum by someone who's username starts with VeeDub!

Anyway... I kept playing musical parts and crowbarred out the PCV valve (rubber grommets are not very flexible at 15 degrees!). Since the grommet did not make it out alive, I just stuffed the new valve in the hose and decided to give it a shot. Started right up and idled fine! It did get a little flaky after idling for a while, I am hoping that will go away when the PCV valve is properly installed with a new grommet. I hope.

I painstakingly searched for a vacuum leak prior to posting and could not find anything. It is truly maddening when you have good spark and proper fuel flow and the dirty sob still won't run. The throttle body is pretty gooey on the inside so I am going to shoot some carb cleaner in to spiff it up a bit, I am sure that buildup is not helping anything.

Thanks again for the assistance. It is VERY MUCH appreciated!!

Glad to hear you made some progress! No worries on posting on the wrong forum