Up and down idle, running rich after warm up

[Wino]

So my mx-3 runs well until it warms up, then the idle goes all to hell. It jumps between 800-1200rpm. at idle and you can smell the bugger running rich plus its burning a s--- load of extra gas.

So far i have check the engine coolant temp- its got the proper resistance
The front O2 needs to be replaced cause it has a reading of .7 costantly.
However i beileve it is something else for these sympthos.

I have not checked the ISV yet or TPS.

So does anyone have any other tips or ideas

Thanks guys

Wino

[jschrauwen]

Ahhh, excellent Wino, you have gone through previous threads....good show. You're on the right track. Replacement of both O2's would probably be in order since they can be had for less than $30 usd from some suppliers. TPS is also a good place to look at too and there's a good FAQ that I did some time ago that should help there. Since you appear handy with a multi-meter that should also be a breeze. A good cleaning of the TB and intake tubing is also mentioned in there and is always a good thing to remove from the equation. I'd have a real good look at the intake tube for any cracks or splits cause that will also cause that roaming idle as well as any vaccum leaks in the smaller hoses. The ISC valve that's attached to the bottom of the TB is usually not the culprit in situations like these. It's used to kick up the idle on cold starts to around 1200 to 1500 rpm range and gradually step down as the engine gets warmer. That's basically all it does and doesn't really have a play in engine idle once it's reached it's operating temp.....touch wood. I've never seen one that would generate a fluctuating idle yet.
Jump on to those things previously mentioned and if after that you still are encountering this problem post back and we can go from there. g/l
John

[hgallegos915]

My car was doing this... when I reset the tps with the diag mode. my problem was that the throttle screw (not idle screw) was a bit open. It would surge up and down. It also did that earlier in the year because of a bad aic valve. You do need to replace o2 sensor. Sometimes it can cause car to go into "limp" mode. I got an ebay o2 sensor for 20 dllrs shipped and it worked , now i get good gas milleage. Also replace fuel filter. I replace mine every year. The slightest backing up to it kiss fuel milleage. I dont know how but it does . Makes the car run weird. I guess it screws with the fuel pressure and ther ecu tries to compensate by changing the mixture.

[Wino]

AIC valve?
What is it? how do i check it?
My o2's have 152 000kms on them so i should replace them anyways.
But i want to check the other stuff as well.
Thanks for the advice guys . Ur great here at this forum.

Wino