Please help!!! (Noob Warning)

[stephen-mx3]

hey Guys,

right, this problem has come up 3 times since i bought the car. brought it to a mechanic and he doesnt have a clue.

The car would normally idle at around 800 rpm when its warm but now its idling at around 2100 rpm, but thats not all. It would then start to rev up to about 2500 rpm and drop back down. It would do that about 20 times and then level out at 2100 rpm again.

Sometimes it can drop down to 1500 and then start reving up and down to about 2000 rpm.

It hard to explain so i took a video of it happening,

http://s261.photobucket.com/albums/ii51 ... CF2975.flv" onclick="window.open(this.href);return false;

I've already cleaned the IAC and the MAF and throttle body, i really am lost!

Any help would be appreciated.

(Limegreen, i know you can help me out with this!!)

[erixon]

Did you check if there is any cracks or holes anywhere in your air intake? This will make this happen... It happened with my cracked intake, if this is the case, either throw some silicone on it temporarily or get a new intake.

[SmoothMX3]

TPS ...

[stephen-mx3]

yep, checked the air intake, and it looks nearly new. its only a 1997 so everything is still fairly fresh.

i was thinkin the TPS but i dont think that wud make the revs jump up and down between 2000 and 2500 though.

thanks though!

[se7en]

you mentioned that you cleaned your IAC....It could still be in bad shape...

7

[SmoothMX3]

Though you are wrong my man...

I had the same problem. Eratic idle (revving on it's own)...
I adjusted the TPS, like other's on the forum told me to try. It's fixed.
The slow hesitation when accelerating... I think that's just the motor. I think it's slow like that until about 3500 to 4000rpm. I was told that's how it was because of VRIS. Kinda feels like the motor finally kicks in at about 4000rpm. If anyone can tell me different, please do.

If your having sputtering type acceleration, That will probally be wires, or even possibly the 02 sensor is going bad... It also could be acouple other things but i would start from there. update us...

[stephen-mx3]

i stand corrected, my apologies!

when you say adjusted, do you mean loosen the 2 screws and turn it slightly anti-clockwise or clockwise?

i was worried alright that the IAC could still be dodgy, i guess ill have to wait until the mechanic man with the computer tells me what is what!!

I think my motor just needs a good clean out, i'd love to have the time and skill to take it apart and give everything a good clean with the dremel!! Actually, does anyone have any trouble spots in 1.6 DOHC that can have dirt build-ups that would be easy enough for a noob to get at? i've cleaned out the TB and its looking shiny, but anything else?

[stephen-mx3]

actually, while i remember, when i took out the TB, a liquid dripped out of the 2 hoses attached to it and the metal connections that are on the TB body, beside the IAC are fairly rusted.

Please dont tell me this is something serious

[umcamara]

First of all... the liquid is coolant. Those are two coolant lines going to the throttlebody, nothing wrong there.

Second of all... your idle is set way to high. Do the prepartion procedure (diagnostic mode) and lower it to below 1000 rpm's. Even with the choke engaged it shouldn't idle that high.

Third... I think the up and down idle thing is an IAC valve related issue. I've got the same issue, and I've done everything but replace that.

[stephen-mx3]

thanks for the info umcamara!

After browsing the online manual, i saw its 2 coolant lines, obviously so the temperature operated valve can determine when to switch off.

Its changed now, its now idles ok, bit shaky but nothing bad. That is until i press the break pedal, then it starts to bounce up and down again between 1000 and 1500, so now im beginning to think its something electronic.

I've replaced the battery with a 540 amp one and checked the alternator.

Could this still be linked to IAC?

[umcamara]

You replaced the IAC valve? It's other intended purpose is to raise the idle when electrical loads are placed on the engine, to keep from stalling. (i.e. when the brake pedal is pressed, etc.)

As mentioned above, spray some throttlebody cleaner all over with the engine running. If the idle speeds up, you've got a vacuum leak wherever the cleaner entered.

Also could be coolant temp sensor related. Some have 2, some have 3.

[stephen-mx3]

sorry, wasn't clear.

What the car is doing has changed!

Im sick of it now and its due for a service and timing belt changed so ill just get it all done in one go.

Thanks for the help though!!