Any Mazda experts out there?

Question

2000 Mazda 626, 2.0L, DOHC, 4 cyl, automatic.
Runs down the road fine. Everything's normal when the engine is off idle.
Problem: Very rough idle and stalls - in or out of gear. 
Compression good, tune up items good, no fault codes in computer.
Throttle body clean, EGR checks OK, idle air bypass checks OK, TPS checks OK, no vacuum leaks found.
Engine starts right up and immediately starts to slow down from 1000 rpm's until it hovers around 5 or 6 hundred, starts shaking and generally stalls within a minute. Consistently gets real rough and stalls at a stop in gear in 10 or 20 seconds unless the throttle is feathered.
I just priced out a few of the items that I thought might be suspect and got a whole new "appreciation" of Mazda - the idle air valve, for instance, is around $500! This is definitely not a vehicle to be replacing parts on a hunch.
Any help or tips are appreciated. Thanks.

Bill L · Accepted Answer

Couple things for you to try, When running take the vac. line off the EGR and observe what happens.Also put vac. on the EGR with a pump just to cycle it makes sure you can turn it on and off with mechanical vac. pump. Also take carb. cleaner and spray around any vac. related lines or seals and look for a hesitation if it starts to stall you found a leak, repair as needed.You could also get a can of MAF cleaner and clean the MAF. Also try unplugging the MAF if it runs better you have a bad MAF sensor or dirty sensor.You could also do an exhaust back pressure test.Just remove an oxy.sensor, your pressure should be below 5psi. If your high remove exhaust at a connection point after your test port and re test.The test should be run at idle and 3,000rpm.Good luck and I hope this helps.

viruz · Answer

don't guess - go to the mechanics. either mazda or someone who could get the answers. then think about if it is worth replacing old parts with new ones. 

believe it or not, in my experience with different cars that was the best thing to do while having different problems. 

because due to the age of the car, ifs or may bes or try's will not get the thing going with no problem at all

jheetman2004 · Answer

fuel pressure regulator possibly bypassing fuel, purge solenoid, if you could scan it when cold to see if the temp sensor jives with ambient air temp that might reveal a problem. those are just my top guesses.

Craig M · Answer

Cheap things to try:

Air Filter.
Put a bottle of injector cleaner through a tank of fuel.

PAUL P · Answer

Hi,
Take a look at the air filter. I`m in canada and we get alot of salt dust and its hard to see.

Anonymous · Answer

I think it might still be in the computer. Try` putting in a new one and see. Reflash if needed.

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Any Mazda experts out there?

6 Answers