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Idle issue

Jet noise

NAXJA Forum User
Location
Phoenix
So I just bought a 97 XJ, 4.0l, auto, 242 t case. It used to be a government vehicle and has 160 on the odo. It ran fine when I bought it, ran smooth for another week or so, until now.

My issue is, the jeep will start and run, as long as I keep my foot on the gas. Take foot off pedal, and she dies. I just will not idle. I swapped the MAP sensor off my 01XJ, and that didn't help.

Looking for pointers on where to look!
 
Check the kick down cable make sure its tight. Easy and free box to check off. Next look for the EXT IDLE switch should be around your fog lights/rear wiper area. Mess with that see if it helps (switch to the other position). Once that's done head down to Orielly Auto if you have one. Rent a fuel pressure testing kit. You're going to have to google what its supposed to be at. Crank it and test to make sure you have fuel pressure and return it.

Even before that check the vacuum on the MAP sensor, fuel pressure regulator, brake booster and the rest of them.

Before you buy new sensors check out strokedjeep.com and shoot him an email. He usually has throttle body sensors for dirt cheap and test them before sending them out. I'm thinking its most likely a vacuum issue.
 
How about scanning it with a computer first?
 
Check the kick down cable make sure its tight. Easy and free box to check off. Next look for the EXT IDLE switch should be around your fog lights/rear wiper area. Mess with that see if it helps (switch to the other position). Once that's done head down to Orielly Auto if you have one. Rent a fuel pressure testing kit. You're going to have to google what its supposed to be at. Crank it and test to make sure you have fuel pressure and return it.

Even before that check the vacuum on the MAP sensor, fuel pressure regulator, brake booster and the rest of them.

Before you buy new sensors check out strokedjeep.com and shoot him an email. He usually has throttle body sensors for dirt cheap and test them before sending them out. I'm thinking its most likely a vacuum issue.



Good info, thanks! I'll do some checking tonight 👍
 
You also need to check the IAC.
 
Any other issues other than it dies at idle?

Could be any of a number of things. Get a volt meter and test the TPS idle position voltage.

May just need a tune up, new air filter (is it soaked in oil?), spark plugs (are they fouled, gap too wide from wear), cap and rotor (too worn and eroded?).

IAC may be fouled and sticking. Idle Air Control. Pull a vacuum hose loose on the intake manifold (use the one in the rear that goes across the top of the engine to carbon canister on the passenger side) and if see it idles with out dying? Ill bet it runs when you do this!!!! If it does, you need to focus on why it is starving for air at idle.

Air filter, IAC, TPS are top selections.

CPS can be tested sort of with an ohm meter, but it is no conclusive.

Check the kick down cable make sure its tight. Easy and free box to check off. Next look for the EXT IDLE switch should be around your fog lights/rear wiper area. Mess with that see if it helps (switch to the other position).

What???? Kick down cable for an idle issue? WTF is an EXT IDLE switch?

Are you talking about XJ jeeps or what?
 
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It sounds like you have the combination of a dying battery and a dirty throttle body. If you clean the throttle body it should fix your issue. Also you might want to get your battery checked.

If it starts and cranks, I would not suspect the battery for an "it runs if I give it gas, but will not idle..." Also it is OBD-II with no codes thrown.
 
Thanks for all the help, guys. I let it sit for a while before I had a minute to mess with it. Today I pulled the throttle body off and gave it a good cleaning. I didn't think this would fix my issue because it wasn't overly nasty. Anyway I cleaned it all up and put a new gasket down. Hooked it all back up and cranked her up. She was rough at first but smoothed right out and runs like a champ now.
 
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