bad idle, cel light on

[integg993]

Just a while back my MSP thew a CEL. My idle became inconsistently erratic and RPM's would drop to zero if i took the load off the engine too fast while driving. Took it to have the code read by a friend who had a reader and it gave P0171(bank 1 too lean). I heard i was a common problem so, i took some of the advice on the forum and cleaned the EGR valve and the MAF. Also checked for any vacuum or exhaust leaks... none found. So i took it to a mechanic and asked him to take a look. He said the upstream o2 went bad and needed to be replaced...200 dollars later the problem is unchanged. I'm Just looking for any more ideas on what i would be before i take it into Mazdaspeed .

[MSP #167]

check the intake manifold gasket, sounds like that may be it, how many miles on your car, they tend to leak after a while and will mess with your idle and cause that code.

to check spray some brake clean or carb cleaner where the manifold connects to the head while idling and see if the idle changes.

[integg993]

it's got 63k. already sprayed down the throttle body down with cleaner, still no change. I had also just recently changed out the spark plugs. Only suggestion one of my friends could make is that my air idle valve was malfunctioning or getting suck. Ever heard of this happening? I was going to clean out but didn't have the proper tools. I bought the car with 39k on it. After all i've done to it, it's now running better than when i bought it, it's just idling like crap

[Flspeed]

I would get all new vac tubing and just replace it all and pressure check your hot and cold pipes.

[MSP #167]

alright try and disconnect the wastegate acuator and plug up the vacuum line on both ends. Do that for a min or so if the engine becomes stable then you need a wastegate acuator.

yea, like flspeed said, replace all the vacuum lines, you may have a leak somewhere that you missed.

[integg993]

i'll give those ideas a shot but, the bad idle isn't consistent. It will only do it once in a while. The "near stalls" only occur while driving. The other thing is. It will go a few days with the CEL on, then CEL shuts off for a few days.Makes it kinda hard to catch the problem. I'll let you guys know what happens. Thanks

[MSP #167]

just cause the cel turns off the car is still having the problem, it is just going into stored memory when the light turns off.