I normally just drive my Protege very short distances (no highway) and had never had a problem.
I recently drove 100 + miles on the highway, and when I got off the highway, the idle on the car was too low, and it would stall out constantly at a stop.

After sitting for 1 day, and in local driving, the idle was fine.

I went to a mechanic---and after a very long long time--he thought it was the "idle air control valve"-
This is $400+ part, and he didn't seem overly confident. Any other ideas? The check engine light has not turned on.


thanks,

 

My first thought is the EGR (exhaust gas recirculation) valve. It does not operate during stop and go city driving. It operates on highway trips when vehicle speed is steady. Depending on what year car it is will determine what kind of valve it is. If you usually do city driving it can get excess carbon build-up on the valve which can cause it to stick open or partially open causing stalling. It usually occurs when getting off the freeway on a long trip and coming to a stop. The valve is used to being open on the highway and the carbon build up does not allow it to fully close. This is my opinion.

 

I would agree that's the first thing you should check.

 

Count me in too for checking the EGR valve for sticking open before throwing a $400 IAC valve at it. Description of when rough idle/stalling occured would match EGR problem.

 

Thanks for all your responses! Is the EGR (exhaust gas recirculation) valve something something that can be cleaned (the carbon build-up) or does it need to be replaced completely?

thanks!

 

I've had about 50-50 luck with cleaning EGR valves in the past. Just remove the valve and use carb cleaner to clean out the chambers. It won't hurt it to try.

 

Thanks again for everyone's help! I will attempt to clean the EGR before trying more expensive options.
kind regards,

 

i dont want to put a damper on the topic but i have recently had the same problem with my protege 1.8. I got the EGR a couple days ago and installed it today. I dont understand how, maybe you guys can help me out hreto, but the symptoms got worse. I would explore all your options, try cleaning like they said and if it doesnt help take it to your mazda dealer. Mine was brand new and didnt help at all. Just some things to be aware of.

 

I wouldn't make the EGR valve the first suspect for rough idling.
I would first make sure the ignition is fine: spark plugs, wires, distributor cap and rotor.
2nd that there is no vacuum leak on the intake side: vacuum hoses, intake hose, brake booster hose, lower intake manifold gasket.
3rd that no vacuum line is obstructed, including the nipple for the EGR boost sensor at the back of the intake manifold.
4th that the MAF sensor is clean.
After all of that I would clean out the existing EGR valve, clean the throttle body and the EGR ports. You need to scrape the deposits out, throttle body cleaner did not help with mine.
And finally I'd check the fuel supply system: pressure and volume, fuel injectors.
Also an engine that has been running short distances only might benefit a lot from a Sea Foam treatment.