Rough idle, stalling, doesn't start

[SOLVED] Rough idle, stalling, doesn't start

This morning my wife was driving to a class and called me saying she had pulled over on the side of the road due to some heavy shaking and stuttering. After turning it off, the car would crank and crank but not turn over. We had it towed home and now I'm trying to diagnose.

It does start, intermittently and idles incredible rough. Sometimes it helps to give it a lot of gas but it is still rough. Idle revs up and down, from about 500 rpm - 1200 rpm (not normal, very low). My thought process is this is likely fuel starvation. It happened suddenly (this morning), no gradual onset over the past little while. That sort of rules out timing belt and fuel filter/pump issues. I'm thinking it's a valve or electronic malfunction.

Edit: Vehicle is a 2003 Mazda Protege 2.0 L LX with automatic transmission and approx 165,000 KM

I just finished taking out the the throttle body and the ERG valve. Pics are attached. They both look a little carbon-y but I wouldn't think they are blocked.

One thing I am concerned about is the normal operation of the ERG valve. I've never looked at one of these things before but it seems to be that it could be stuck. If I push it down, the spring does not pop back up. It sticks and needs to be pulled up. Here's a video that shows what I mean: http://www.youtube.com/watch?v=00cE1gU4d38

This guy simply blocked off the valve to see if the engine would return to normal:

http://www.youtube.com/watch?v=8YRq2Xl58Oo

If the egr is stuck, give it a good cleaning.........also change your coil packs and plugs. Problem should go away with those three. What you have is a common problem.

Hi, appreciate the response. I was on hold for a while waiting for a gasket to come in. The old throttle body gasket was toast and just installed the new one. Replaced both coil packs and all plugs. I had also taken the EGR valve off and given it a cleaning. It was sticking when I first took it off but after the cleaning + a little oil it was moving freely and the spring was working fine.

However, after putting everything back together, I still have the same result. It will start if I give it gas, but as soon as I let up it idles very rough around 200 rpm and then stalls out. There is no CEL when running (obviously the engine light goes on after the stall). I don't have a code reader and can't really get it to a parts place for them to read it. Ideas?

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. 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. Thank to all you provided input.