'96 RAM 1500 5.9L SLT 4x4 suddenly won't idle this week.

As dumb as it sounds, have your battery tested. That's a classic symptom of a battery starting to loose it.

Denny

I doubt highly it's his battery hold-down, Denny... and even if the battery wasn't tight, it wouldn't cause the erratic idling.

On the other hand, if the battery were "LOSING" it's ability to hold a charge, well... then you may be on to something!

:^)

It could be. If the battery was rattling around all the little volts inside it get scrambled up and forget which way they were headed and after they're good and lost the engine don't run right..

Denny

In addition to Denny's battery suggestion I'm going to suggest a can (or two) of Techron injector cleaner. I've seen that stuff clean up some really odd idle problems around here.

Couldn't hurt... but the fact that the engine holds idle when slight accelerator pressure is applied indicates that the idle air control motor isn't allowing enough bypass air around the throttle plates, due to the lack of voltage from the battery, and thus requiring the throttle to be opened up slightly to allow the proper amount of air into the intake.

For the OP's benefit... your question about a failing choke isn't far off the mark... in the EFI world, there's no "choke" specifically, but there is an Idle Air Control motor... this is a little stepper motor on the throttle body that drives a pintle back and forth, and regulates the amount of idle air that's allows to pass around the throttle plates, so that even with the throttle closed off, the engine gets enough air to idle. That IAC motor is controlled (as is everything else) by the computer. However, the computer is very sensitive to voltage... give it too little voltage, and strange things begin to happen... one of them is it's inability to properly position the IAC motor, thus preventing enough air from getting into the intake.

Step one is to load test the battery, and exchange it if it won't hold a proper charge. Step two is to remove the IAC motor from the throttle body (I believe it's on the back side, closest to the firewall), held in with a couple of Torx screws. While holding the motor, with the electrical still connected, switch on the ignition. If operating properly, you should see the pintle fully retract, then fully extend, then settle somewhere in the middle of it's travel. It should operate nice and smooth. If you notice any stuttering, or if it looks really fouled up with carbon and such, disconnect it from the electrical line, and soak the pintle end in some carb cleaner. If it still doesn't operate correctly, it's time for a new one.

While you're there, it wouldn't hurt to give the throttle body itself a good cleaning... unlike a carburetor, your throttle body is "dry" - only air passes through it... no fuel to help wash away crud. Over time, you get some nasty build-up around the throttle plates. Throttle body cleaner in a spray can works, but I prefer the type of cleaner that comes with foam swabs (they look like marshmellows) that you soak in cleaning fluid and hook onto the end of an applicator. That lets you really swab out the inside of the throttle body, and I think it does a better job of cleaning.

You know, I halfway wondered about that. About a month or two ago when it was colder, I noticed a hesitation once or twice when cranking on cold mornings. I'll check the battery... Thanks everyone!

That lets you really swab out the inside of the

Tom

Cleaning the throttle body says to me, that one cleans out the interior of the throttle body. So how do you gain access to the interior of the throttle body? I have a 2001 Chrysler LHS and a 2001 Dodge V8 PU.

Thanks Bob AZ

here is the product i like. it is made by 3M and does a fantastic job without having to dig around in you fuel system with a spoon.

it requires a specific hose and regulator kit that isn't cheap but the money saved by doing the job yourself will make up for the hose/regulator/canhanger.

you inject the cleaner while the vehicle is running and it will smoke like a freight train so don't be up wind of a gripy neighbor when you decide to give it a whirl. my trucks will start getting a rough idle about every 80k and i'll pull out the air cleaner and clean it. then i run the 3M system and i am good to go for another 80+k.

we have our own fuel tank and only stock premium fuel but if i end up having to buy fuel out in the wild and get a bad load i feel it immediately. when this happens i load the fuel up with isopropal alcohol and after a couple of clean tanks i run the injector cleaner. this is one instance where the ol "mechanic in a can" is a good thing. michael

EGR valve stuck with carbon. Ruins idle. exact symptoms you describe.

Remove and replace or you can try cleaning...