5.9 360 high idle

[willis923]

alright, so the ol girl has been problem free all summer, and now that cold weather has rolled around, i was waiting for something to start going janked.

98' ram 1500, 5.9 360 mag,

all started the other day, drove it to town, no problem, got dropped off at my grandparents and let my mother take it to work around the block. came to pick me up that night, and it was idling way high. figured it was just cold. hasnt done it since. now, today, i drove it to town again, hardware store, grocery store, lunch and back home. got to the hardware store, idling fine. (about a 20 mile ride, up to full op. temp) ran next door for groceries, and it was back to idling around 1500. shut it down, cringing, shopped, came back out. fired right up, idling normally. drove maybe 10 mins down the road for lunch, put it in park, and boop, right up to 1500- now im getting pissed off, so i give it a solid rev to about 3500, and it idled down to about 1000, slowly came back up. pumped the brakes to see what would happen. and it did slowly climb to about 2000. after i let it set for a min, it dropped back down to about 1200. that makes me think its vac related. i know this truck has a vac issue somewhere, as it has "wild vents". any ideas guys? i have yet to look into it, thinking either TPS or vac issue somehow.

 

[rowdyram]

Possible IAC fault

 

[willis923]

Possible IAC fault

is there any ways to test for that, or just throw parts at it. be advised, CEL is not on

 

[tommyboi87]

Mine did the exact same thing the other day. (5.2 Magnum) Like Rowdy said the IAC is a good place to start. Try cleaning it first. It's on the back of throttle body, and you'll obviously have to take it out to clean it. If you do clean it, don't push or pull on the tip thing (whatever it's called. You'll mess your idle all up.) Just scrub it with a good throttle body cleaner and an old toothbrush. Let it dry reall good, reinstall, and see what happens. Worst case, you'll have to buy a new one, which I had to do, which is like thirty bucks. Does it idle high in gear also?

 

[Yeret]

I had the same problem earlier this year. I started with the IAC valve and the old one was coated quite thick with gunk. I bought a new one and haven't had a problem since.

EDIT: I scored a new one on eBay for $10. Sure, it's a Chinese-made deal (hell, what isn't anymore?), but it's an easy part to replace so even if it fizzles out in a year, it's not a big deal to me to buy another.

 

[willis923]

no, not in gear. only park or neutral. with any light strain on the engine, like turning the steering wheel and makeing the PS pump work, will bring it down a good amount. A/C kicking on makes it shoot up to about 2 grand. i'll try the IAC and see what happens. what stumps me is its intermittent so far

 

[tommyboi87]

If it's only in park and neutral, I'd pull the IAC and have a look at it. It's probably gummed up real bad. When I cleaned mine, It lowered the idle a good, bit, but not back to its norm. So I went ahead and bought a new one. I think you might have to have it dialed in if the PCM doesn't register it. You're supposed to gap it out to make up for the gasket width and whatnot, if it isn't already set.

 

[rowdyram]

Clean the IAC pintle ant the passages really well and also clean your throttle body. Pull your negative battery and touch it to the positive for 10 seconds. Re-connect and cycle the key 2 times before starting. That will clean the idle adapt and will begin to relearn. Drive it for 4-5 miles and recheck your idle.

 

[willis923]

Pull your negative battery and touch it to the positive for 10 seconds.

that sounds like a terrible idea. dont get me wrong, i love vehicle fires, but id rather not be responding to my own truck...

 

[willis923]

also, one other thing i noticed, its done it a few times. i was jumping another vehicle, a 2009 Case 580 backhoe, and i held the accelerator down a bit, to about 2k rpm, and it would surge between 1500 and 2000. IAC cause that? if i take it out and clean it, is there anything i should be careful of besides the obvious dont muck up the gasket.

 

[tommyboi87]

Was your a/c on or anything while jumping? When you take the IAC out there's a little tip that sits on a spring. There's a name for it but I can't think of it. Try not to push or pull on it because that's what controls your idle. I think pushing in makes it idle higher and pulling out lowers idle. I used an old small wire brush and some throttle body cleaner. Wouldn't hurt to clean the throttle body where if it's gummed up too.


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[willis923]

Was your a/c on or anything while jumping?

headlights, heat, yellow LED bar light, but thats it. nothing that would draw vacuum or put excess strain on the engine. oh- the fan was cycling on and off. the previous owner must have put in a heavy duty fan clutch, but it was on for maybe a minute and off for about 5. it was surging the whole time though, fan had no affect

 

[rowdyram]

Touching the cable together won't cause a fire... If the battery is not hooked up there is no current in the circuit. What it does is discharge the capacitors in the PCM. I do it with every Chrysler after IAC or throttle body cleaning. That is how you reset minimum air flow values

 

[willis923]

oh, ok. didnt realize both got disconnected. my bad

 

[rowdyram]

You don't have to disconnect them both but you can... Anyway any update?

 

[willis923]

no, im going to work on it over the weekend. i still only have my learners permit (cant get a road test date until another month and a half) so its not a rush to get it fixed, truck dont get driven daily. my father wants to take a look at it before i touch it.. he insists its something else, but time will tell

 

[tommyboi87]

It doesn't sous like much else. Unless somebody tried to mess with the idle screw which would be hard. Or the throttle body positioning sensor. But I don't think it's that either


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[Mr_nice2570]

Hey hope some one can help i brought a 96 dodge ram 1500 4.2 and I have the exact same problem as this, idles high in park and neutral (around 2,000rpms) then when put into drive or reverse the rpms drop to around 1,000-1,200 any ideas or solutions??