Rough idle

When my 99 mazda 626 is at operating temp it idles rough and stalls sometimes in park, when at a stop light in drive it idles better. When I unplug the mass air flow sensor it idles fine! Should I replace the maf sensor? Some one told me it could be the air temp sensor in the airbox. Replaced the plugs, pcv valve and hoses.

I replaced the mass air flow sensor and still the same thing! I'm not sure what is is. If you unplug the maf sensor still it runs better! Could it be a vacuunm leak?

No check engine light on. Where should I start should I try to clean the iac valve? Where is the egr valve located?

I cleaned the iac valve and the egr valve. The egr valve was filthy! I put a new throttle body gasket on and started t up and went for a 20 minute drive. It idled great!Plus the exhaust wasn't making a puffing sound anymore. When I was driving it was sputtering a little bit. Is this because the computer needs to reset the settings?

NEVERMIND! I took it to the store and wouldn't you know. At the stop light it started loping again, and I floored it and it backfired a little. The popping in the exhaust is back. Does a mechanic do a reliable vacuum test?

Thanks for your help! I broke down and got it checked for a vacuum leak, and the intake manifold gasket and the injector orings needs replacing. He is charging me 300 for both things.A coouple of garage mechanics quoted me at 200 plus parts. Do you think this is a fair price?I guess its worth it to get it off my mind!Thanks again.

My daughter drives this car while she is away @ college. We recently replaced her timing belt and water pump. When we picked it up from the mechanic, we were told one of the engine mounts was broken, the car would run, but it would be rough while in gear but not moving (say like at a red light). Boy was it rough. We had the engine mount fixed, but it is still rough while in gear and stopped (again, red light) but much improved over what it had been. When the car is moving it is smooth and sweet. Lately she has had a check engine light come on and the auto 'zone' type stores tell her she has a mis-firing 3rd cylinder. We have all new spark plugs and wires. I put some slick 50 fuel injector cleaner in it about 300 miles ago. Are these two things related? Could the rough idle be a transmission problem (it's about the only thing I have not fixed/replaced on this car yet! ;- )

So you don't think it is the transmission? That would be a relief!

Besides the fuel injector cleaner, what do you recommend for my next step? The spark plugs and wires are new with in the last month. It just passed it's safety and emissions inspection too. (Passed the day before the engine light came on, and 5 days after the code had been previously cleared.)

We get the 85 octane gas. Because of her high mileage should we buy the higher octane gas?

I'm trying to determine the cause of a rough idle. The check engine light came on and a mechanic traced the codes to the Idle Control Valve, however, I've been noticing on forums that this model is particularly susceptible to vacuum leaks that can cause rough idling. I've also noticed under other threads that a boot should be inspected for cracks, however, there is conflicting information as to which boot should be checked.

Note - Before the check engine light came on the idle fluctuated enough that car would almost stall at traffic lights. At that point the mechanic manually brought the idle up for a quick fix (the light came on a few weeks later).

Furthermore, if the A/C is on at highway speeds, the car's power seems to hiccup sporadically. Not sure if this is a related issue or not.

Any suggestions?