Hi folks. First post here. Common problem it seems, but I wanted to run it by the forum anyway...

1995 Protégé with 1.5L, automatic. Terrible rough idle at cold start-up.. chug chug chug. After 5 minutes, it’s warmed up and idles pretty smooth. Even then not perfect, but drivable. Not throwing any fault codes.

I have removed and cleaned the EGR valve. It was sooty, but I cleaned it up as best I could (you can’t actually disassemble the valve, unfortunately). I also cleaned the MAF sensor with MAF cleaner. Inspected hoses.. the car was garaged and very clean and I can’t see anything wrong with the hoses.

These things did improve the idle somewhat, but it still has a ways to go to be completely normal. What next? Should I go ahead and buy a new EGR valve? Sure hate spending money on parts that don’t need to be replaced. Any suggestions greatly appreciated. Thanks

 

I hate buying parts and not knowing if they solve the problem. I suggest you carefully read through this guide and do the cheap and easy stuff first.

https://www.mazdaforum.com/forum/maz...%E9g%E9-31136/

 

clean the throttle body. First disconnect negative terminal of battery (hope you did this when you cleaned the MAF). You need to do this as you will be moving the butterfly throttle opening to spray stuff through it.
Best to slightly remove throttle body and put paper towels, rags on other side to catch most of crap as you will spray it vigorously with throttle body cleaner. Make sure to replace that gasket/o-ring between throttle and intake. try to clean up intake plenum entrance as well.
Inspect the intake hose for cracks.
Change the PCV valve as Mazda doesn't.
Re-connect battery.
Let idle for 5-10 minutes after before driving.
put some fuel system cleaner in the gas tank.
Check you air filter, time to change?

 

OK still at it, but here is a new finding..

I see there is a hose connected to the idle air control value that taps into the coolant. I don't know what it's for or what it does, but, the heater in my car is not working. That got me to thinking if perhaps the 2 problems are somehow related...?

Going to pull the heater hoses tomorrow and see if there is a blockage I can clear up.

 

Another update.. I remove the BAC from under the throttle body. I performed the "hot water" test per the Protege shop manual. I do not see the value moving when going from cold-hot-cold. In fact, it appears to be stuck in the closed position, which I believe is the "hot" position. This may explain the rough idle when starting up cold - that valve should be open when cold, not closed. Anybody else had this problem?

 

maybe this thread takes you a step forward:
97-98 IAC Valve Clean Out with Pics

 

Now I'm completely stumped. I bought a replacement IAC valve and... no change at all. Still runs so rough on cold start it will die. Once warmed up, it's acceptable and will drive OK. But whatever was wrong is still wrong. Super frustrating. Any other ideas greatly appreciated.

 

How many miles do you have on it, how old are the spark plugs and wires? Did you clean the EGR passages in the intake manifold as well? How about the nipple to which the vacuum line for the EGR Boost sensor attaches. Is it clear or clogged?
Is the valve cover gasket good or do you find oil at the bottom of the spark plug tubes? How old are distributor rotor and head?
Did you check for vacuum leaks?
Is the fuel pressure good? Is the fuel pressure regulator leaking fuel into the intake?
Does the throttle position sensor work smoothly?

 

It sounds like you have a vacuum leak. Cold engines need to run rich until warmed up. Possibly the intake gasket since you say the hoses are fine. Warm the engine up and spray flamable brake cleaner around the intake etc. if the idle changes you found your leak.

 

Ok I'll try that. Since my last post I have taken the TB and EGR off again. This time the goal was to really clean the EGR passages. So I did that - both to and from the valve. Used carb cleaner, mineral spirits, shot the stuff through the passages with compressed air. Unbelievable amount if black gunk came out. Had me thinking the passages were blocked enough to be the culprit. Took off the pipe from the exhaust side and cleaned all that out too.

Results: better, but still not right. It starts and runs better, but until it's hot, the idle chugs and chugs. The car is drivable like that, and it only takes 5 minutes to warm up, but I'd still like to find the real smoking gun.