idles high

northern ranger · Dec 3, 2010

Hi, I have a 94 2wd ranger 4.0 5spd and when i start the truck it idles high around 2000 rpm then after 30 sec or so it comes back down. Also sometimes when i push in the clutch it idles high before returning to slightly less then 1000 rpm. What could this be? When started cold (outside temp is 40+ degrees) it blows a little bit of gray smoke from the exhaust but not to bad, as it stops upon warming up. Thats probably normal I would guess but I'm not sure. Any suggestions?

Yellowsplash · Dec 4, 2010

It is normal for the engine to idle high on a cold start. As the temp of the engine gets warmer the rpms will lower in stages until its at full operating temp. The ecu also does this when the vehicle is moving and you push in the clutch...rather than the rpms falling rapidly to idle speed, the ecu idles the engine high to facilitate a smoother shift if your shifting gears, or a smooth transition to idle speed if your coming to a stop. Once the vehicle stops moving it will lower to normal idle. You can clean the IAC valve with carb cleaner if you wish, but it sounds like normal operation.

northern ranger · Dec 4, 2010

Thanks for the reply. I'm no mechanic (only know what i fix) so I guess just being an older truck than my other rangers it might just be a little bit rougher. But when i start it sometimes it will idle high quickly then sputter and die. Then next turn of the key will start it normally. What could that possibly be? And what could be producing more dark exhaust fumes then one would like? Thanks again.

Yellowsplash · Dec 4, 2010

A few question I'd ask is do you notice any fluid loss, oil or antifreeze? Does the vehicle run fine when driven?, under heavy load? Do you get a puff of dark smoke after you've stopped the engine for a short period of time, but not long enough for the engine to cool (ex. stopping to get gas). These questions will help narrow it down some.

First thing I would do is the obvious....check for vacuum leaks, check vacuum line running to FPR, make sure FPR isnt faulty by removing line and checking for fuel, etc. I would also recommend running some seafoam in the brake booster line slowly as to help clean the inside of the engine....have fun watching the smoke show. Then if needed, change the plugs as they can become nasty from all the burnt carbon.

northern ranger · Dec 4, 2010

I do loss antifreeze every so often. A couple times it seemed a little much but i thought maybe i just added to much from losing some beforehand. It does run fine when driven and i haven't had it under a heavy load but plan to when I move across country( the move explains my anxiety about car issues ). Also I do get some exhaust smoke after its started from sitting for a short time.

Yellowsplash · Dec 6, 2010

I would do some routine maintenance as described above, especially if you havent done it before or are unsure how long ago it was done. Anytime I break into a vehicle I havent worked on before I always start with the basics and get them outta the way. Staying on top of that will help prevent alot of issues from popping up later on. In addition to the above, go ahead and clean the MAF with CRC's MAF cleaner, change fuel filter, etc. Most problems that come up on this board are easily fixed with routine maintenance that has been failed to be performed.

If it gets worse let us know, but for the most part our engines are known for cooling system issues such as heads cracking and intake gaskets leaking. My advice is if its still running fine, keep running her and make sure to keep the fluids topped off. My exploder has 220K miles on it and suffers from some coolant loss. It runs absolutely fine, and quite well for its age and mileage, but losses a bit of coolant from time to time. Been driving like that for 50k+ miles. Until I start seeing other indicators or it starts running bad, I wont waste my time tearing into it...I have too many other projects to deal with anyways.

idles high

northern ranger

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Yellowsplash

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northern ranger

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Yellowsplash

Well-Known Member

northern ranger

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Yellowsplash

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