Truck is stock with 110K miles.
Wed-Fri it wouldn't idle until completely warmed up. It just stalls as RPMs
go to zero unless you keep your foot on the gas a little. Drove fine when
Sat it had same problem several times even after warmed up.
It's always run great other than this happening now.
Any ideas, anyone? EFI doesn't have a choke that could fail, does it?
Any help would be greatly appreciated.
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.. <BG>
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
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.
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.
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
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.
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