Car Idles way too high.

[Rukus]

My car tends to idle a little too high than what it should.. like 500rpms too high. It revs at 1400 rpms when it settles everything all out. Normal idle is around 800 or 900.

When its cold, it will rev up to 2000 and sit there revving like its hitting a rev limiter and as it warms up, i will rev down to 1600 and then to 1400. and if i am REALLY LUCKY it goes down to normal idle revs!!!

I tried replacing my idle air control valve and module, but That never fixed it.

Dows anyone havea clue why my car b ehaves this way? Could i need to replace my temperature gauge sending unit as well? (when i disconnect wires from it, my car revs up)
I have no clue what is going on here.

Any info appreciated. Thanks.

 

[mjbst111]

check vacuum lines. heck it could be anything. I took off my oil cap once while it was running to add oil on the fly and the idle went nuts.

so in short: I have no idea.

 

[jrt67ss350]

I doubt it's a vacuum leak. Vaccuum leaks tend to make a car idle slower. If you take your oil cap off or remove the dipstick when the engine is running, the idle will slow down, and the engine may even stall. Since these cars don't have PCV valves, when you create a hole in the crankcase (by removing the oil cap or dipstick), you create a MAJOR vacuum leak.

Sounds like an engine management issue to me, but I'm not sure what. If you weren't getting a signal from the temp sending unit, I would think the computer would just default to the cold start up routine, in which case, your idle should be about 1100 rpm (at least that's what mine idles at after a 20 degree F start). After it warms up a little bit, my idle drops back down to about 800.

 

[KC Ron Carter]

Hmm,

Lots of oxygenated fuels around these days.

Here is a link on idles.

Have you met Sam yet?

http://www.mesaperformance.com/faqs/idle.html

Pay particular attention to the part about making an orffice with a 1/4 inch hole to restrict the maximum RPM possible.

I use a rubber washer and it works great.

Later,

 

[wood_e]

A vaccuum leak can cause a car to idle slower and sometimes faster. It depends on the car. I would check your vaccuum lines by spraying some carb cleaner on them and listening for leaks.

 

[bahnstormer]

is it idling high when its cold out? its supposed to do that....

 

[Rukus]

The car idles high no matter is its 30°C above or 30°C below.

The TPS is in the proper position, it clicks into idle-on, idle-off and WOT properly.

Also the ECU isn't what controls the idle, from my understandment its, the Idle control module in conjunction with the idle air valve. They both seem fine. The Coolant temperature sensor FOR the ECU exclusively is fine (brand new last year) but there is also ANOTHER temperature sensor for the gauge/idle control ( i beleive?) that may be the culprit like i said before. as when i d/c it, the car instantly idles a little faster.

The fuel part of the air/fuel ratio should be fairly constant from my understanding, basing itself on engine temperature, adjusting the fuel part of the fuel to air mixture accordingly. What the problem is, the car is getting too much air at the idle air control valve (or idle air bypass valve) i did a quick test and clamped down on the hose and hte car idled right down properly. Sometihng is keeping that valve open way too much, and i can't pinpoint it down to anything.

Thanks for all the info.

p.s.: my car does have some oil leakage, and valve seal problems (gets a bit of blowby). Could this affect idle?

pps: also i want to unaffect the cold idle and start as LITTLE as possible, as it CAN go down to as low as 40°C here, and i heave heard of the washer trick. I don'tthink it would work for me.

 

[wood_e]

Your idle air bypass valve probably needs replacing if it is being kept open too much by its own mechanism.

 

[Rukus]

also, i did the trick where you disconnect the wire on the end of the idle air control valve and my car just revs like a rev limiter at around 2000 - 2200 RPM, and doesn't fuel cut down to 600 rpm, like i hear its supposed to do.

 

[bignate]

There is a screw that you can turn to adjust the idle level, but it will still rev at the beginnig, that shouldnt be a problem tho

 

[Rukus]

that screw is all the way closed.
I will look into Kc Ron Carters artivcle some more, i browsed through it and it has some VERY helpful information. If i find out what it is, i will be sure to post it for others to know.

Thanks

 

[junglestylz]

If you need any parts for the car let me know. There are a couple of things that will do this. The vaccuum leak, the throttle position switch, the idle control valve, and the time temp sensor will all do that. I have an aftermarket non electronic Idle control valve if you need another one. It is fullyadjustable, and it will almost always take care of the problem.

 

[Rukus]

KC Ron Carter

how does the restricting of airflow work with the washer? does it affect how the car runs while in idle-off? i thought that the Idle control valve would CLOSE when the car is not in idle position, (TPS idle off Gas pedal pushed, RPMs jigher than idle) to restrict airflow of unmetered type into the intake manifold. Does the bit of air going into the intake manifold affect anything? or does the ICV even close when its not needed?

Please get back to me with any info on this.

Also i live where it gets to 40°C below, how will this affect my cold starts? will i just needto sit in the car and coax it for a bit until it idles properly?

 

[Rukus]

junglestylez, how does the manual ICV work? would it be the same as jsut putting in a valve to help restrict airflow in front of the Idle control valve?

 

[KC Ron Carter]

Restrictor

Using an inline restrictor affects very little.

It restricts the maximum possible and forces the idle valve to a new location.

I have used it on many e30 engines for the last three years.

I can remove it in the summer, but when they start selling the winter oxygenated fuels I find my idle staying high. Installing the restrictor will give a stable idle with no other changes.

Later,

 

[Rukus]

You said in the summer you cna remove it! But on mine, in the summer, myu car STILL idles high! what is this???

 

[KC Ron Carter]

Fuels vary

In the USA Midwest the vendors have two fuel mixtures.

The winter fuel is different to meet the US EPA standards.

It will even be worse next year with the phase out of MTBE.

In USA they will use Alcohol as an additive, the last time killed lots of Bosch Fuel injection systems.

Later,

 

[Rukus]

That makes no sense to me.
Sorry.

 

[equate]

mine idels really high when I do a really cold start, it will be about 1200 or so until the enginee warms up then it will go back to 500

 

[Rukus]

equate, that is NORMAL. consider yourself lucky.



althought i would adjust warm idle to a bit higher on the Idle control valve, to like 800rpm