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Kabeiroi

Iac Valve Failure Symptoms?

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I have a 1993 2.0L 4 Cyl. Mazda 626. The idle has been getting fairly rough lately. Runs fine while driving, though.

I checked all the usual places... bad spark plugs, dirty air filter, cracked hoses. I even went as far as to clean the IAC valve (which was fairly dirty) and reset the ECU. Nothing seems to be helping.

I pulled the IAC valve back apart to make sure I didn't screw up anything. Everything looked fine so I put it back together. In my haste I forgot to put the little piston back in. The next time I started the car I noticed that the engine smoothed out immensely. I was feeling pretty good until I noticed the little piston a day later. So, I put the piston back in the IAC valve, but the engine still idles horribly.

So, I was wondering, what are the symptoms of a bad IAC valve?

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Your IAC valve is probably at fault. If it has never replaced it since 93' I would consider it getting 'old' ( mine is old and it's a 98 valve .....a little different than your's).

Symptoms:

a) rough idle (for my 98' model the idle should be at approx. 700-750 in 'Park' and warmed up)

B) 'codes' indicating problem with IAC valve ;

c) idle is still rough after cleaning (usually when stopped at stop light and while A/C is on);

d) resistance is out of recommended values

(I don't know what the resistance is for your valve?......check Haynes manual or local dealership ?)

If your car runs better without the 'little piston', then I would try running without it for a few days and see if it causes any operational problems???..... I think the worst thing will be that your car will not idle and stop... just be prepared if that happens.

In the meantime, I would do:

1) start looking for a replacement;

2) make sure that when you replace the valve that you also replace the gasket(s);

3) try cleaning the MAF unit as well.

Good luck!!

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After going through two used IAC valves, I finally had to break down and buy a new one. I got it from Mazda for $453.00. Works great now. When the IAC started to go bad, my idle was terrible. The car was revving very high, high idle, etc...Not good for many other parts. Replacing it was easy. I also changed the gaskets, screws, TB hoses and the same for the TB.

If the IAC is bad, cleaning it will not do much good. I also got a CEL DTC error code.

P.S.

The IAC valves they sell on Ebay, if they say that its reman'd or Used, beware. I got my money back thank goodness, the IAC I bought on Ebay was DOA. It was used.

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Thanks guys. I played with it all weekend and as far as I can tell the IAC is doing exactly what it should be doing. However, I found out that the engine timing does seem to be off. I've made a few minor adjustments and managed to smooth it out some, but the RPMs are still a little bit too low. I was considering pulling the distributor and trying to reposition it. That's something I'll probably save for the weekend.

Any ideas what could have caused this?

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I was also having starting problems after the IAC replacement, and after fixing the starter, ignition switch and a new battery, the distributor finally went. It had been dying slowly over the past two years and it finally went. The distys on these cars, I've heard are known to fail.

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most likely an air intake problem. make sure all of your black intake housing materials are good and that there are no leaks after the MAF. make sure all intake gaskets are good. the main intake gasket, the throttlebody gasket, everything. there might be a cracked vacuum hose too. check the PCV tubing is okay. if there is any hissing, it's most likely a vacuum leak.

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After going through two used IAC valves, I finally had to break down and buy a new one. I got it from Mazda for $453.00. Works great now. When the IAC started to go bad, my idle was terrible. The car was revving very high, high idle, etc...Not good for many other parts. Replacing it was easy. I also changed the gaskets, screws, TB hoses and the same for the TB.

If the IAC is bad, cleaning it will not do much good. I also got a CEL DTC error code.

P.S.

The IAC valves they sell on Ebay, if they say that its reman'd or Used, beware. I got my money back thank goodness, the IAC I bought on Ebay was DOA. It was used.

Hi mr8S1 where did you buy that IAC valve for your car mine is exactly like yours, I have tried everything, cleaning IAC valve etc, but no good results, my IAC valve needs replacing, this is the one my car needs http://www.ebay.com/...3#ht_2844wt_932, but after searching for it everywhere all the stores on line offer this one which has a different inside structure, will that matter and work properly? http://www.ebay.com/...#ht_2948wt_1275, thank you. I will wait for your reply soon. if everybody else can help me fugure this out I will appreciate it very much indeed.

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