as long as spring isn't broken, seal is good, movement is good it should be alright. The pressure or vaccuum when it's installed should aid it.
logging off now.

 

anjp: Just clean everything, get new gaskets and put it back.

I clean an EGR valve by scraping out the deposits. The solvents had no effect. Also clean the EGR passages in the throttle body. you may use B-12 Chem Tool, but don't let it go on the inside walls of the throttle body barrel. Those walls are likely coated and the Chem Tool could remove the coating.

If that doesn't fix it wait for a CEL to appear.

Take a deep breath, Darth Wader!

 

Back again. I was on hold for a while waiting for a new throttle body gasket (the old one was toast and had to replace). I've installed new coil packs, new plugs, wires, and pcv valve to no avail. Everything looked good when I put it back together (with the exception of the previously mentioned EGR valve sticking). I also cleaned up the EGR valve with carbon cleaner and added some oil to the spring mechanism, and it was working fine back to the spring loaded position when I reinstalled it.

I'm still having the same problem: starts only if I give it gas (about half way depressed) and it will not stall out as long as I give it gas. Once I remove the gas it goes into a rough idle around 200-300 rpm and stalls out. Still not CEL while running (obviously the engine light comes on after the stall). Ideas?

 

Have you looked at this?
98-03 Mazda 626 Protege 2.0L Idle Air Control Valve IAC OEM

 

Yes I know that one possibility could be the IAC valve. However, I do not know how to test to confirm it is faulty/good.

 

Well, problem is solved. I'm not 100% sure what of the fault, but here it is:

I'd been thinking that it was the IAC valve, because that's what controls the idle. And because it's one of the first steps in the service manual for this rough idle/stall problem. I took it out, cleaned it again, and put it back in. At this time I also noticed that I had mistakenly put in the old PCV valve instead of the new one. So I swapped that immediately. I don't think a faulty PCV valve gives these symptoms... but it had never been changed before. When I fired it up, it started and idled like a charm. Took a test drive around the block, waited for the temperature to warm up and then took a full throttle + lots of stops cruise down the country road. No problems, everything's great.

So I'm not sure if the final fix was the IAC cleaning or the new PCV valve. In case anyone has a similar problem, here's everything I did:
- replaced spark plugs
- replaced coil packs
- cleaned EGR valve with brake clean and old toothbrush (the spring was stuck and the valve was constantly in the open position).
- oiled EGR spring with penetrating rust inhibiting lubricant so valve springs back to closed position.
- cleaned throttle body with brake clean and old toothbrush
- replaced throttle body gasket
- tested resistance at IAC valve (should be between 7.7 and 9.3 ohms)
- tested resistance at EGR valve (should be between 20 and 24 ohms, between terminal combinations: C-E, C-A, D-B, D-F)
- tested voltage at throttle body sensor (should be between 4.5 and 5.5 volts when ignition in "on" position)
- cleaned IAC valve with brake clean and old toothbrush
- replaced PVC valve
- re filled coolant system (I had drained half of it in order to take the throttle body off without any leakage)

I believe that's it. I'll mark the thread as solved. Thanks to all who gave input.

 

Well, glad it is running!

 

You should be good for a long, long time!
If you are a perfectionist you may consider giving it a Lacquer Thinner treatment: when the tank is half full add 4L of lacquer thinner (NOT PAINT THINNER!) to the tank and drive about 100 miles with a few good pulls up to 5000 rpm. This cleans out the deposits that formed while the engine was running rough. I got quicker starts and better throttle response in my high mileage cars. It cleans the catalytic converters too.

 

That seems a little risky. Isn't lacquer thinner an incredibly strong solvent? At first thought, I'm worried about any plastics or seals it would come in contact with while running through the engine.

Where did you hear of this treatment and how long ago did you run it through your car(s)?

 

I did this a few months ago, but used 2 litres.

HERE: