CEL P0171 and Engine Stall Related?

the EGR valve or sensor? hmm, I didn't realize that there was a better version or the stock part, what's wrong with the stock one? does it just cake up with carbon and stuff a lot or what? and actually I might not have that anymore, I think I gave that too Ken at PG when he bought the TB, I'll have to check
 
the EGR is the valve thats under the throttle body, im drawing a blank on the sensor with the TB... IAC maybe. basically (from my understanding) the stock one in the US gets condensation stuck in the valve then it rusts, badly. canada had the same one, but mazda issued a nationwide TSB that allowed for free replacement with a tremendously improved version. thats right - if you have a MSP (dunno about other gen3 MP's) you can drive it to the dealer, have them order it, and get it installed for free. in CT upstate ny etc etc we arent so lucky. mazda revised the US EGR twice to make it suck less, and failed twice. they didnt want to admit it though (or possibly emissions issues), so their third attempt is still the "stock" part in the US.

you can clean the EGR... well a lot... yearly maybe... and still have it fail sooner or later, or you can buy the CDM one and be done with it. its been on my list as something i want, but im not positive if mines bad. im getting really close to having the car where i want before i start modding, CDM EGR would be a nice addition.
 
quick question, until I get this fixed, if it is the EGR valve, would it be ok to tune, or will it screw up the afrs in boost? or is it just at idle..
 
i believe only at idle and while cruising, i think its fully closed under WOT. wouldnt be the first time if i was wrong though.
 
cleaned that EGR valve until it was clean enough to eat off of, soaked it in carb cleaner all night, used a wire brush on it, and steal wool, and used about 3/4 a bottle of shop size carb cleaner.. after a PITA time getting my coldpipe and stuff back in (long story, see short version on "what I did with my MSP today" thread) but it runs great now, right around 14.7-15.2ish and even turns really rich faster in boost, it's kinda cold out still, so time to tune this baby now that it's running good.. can't wait for some warm/non rainy weather to tune it this week


leex... any update on whats going on?... I would suggest the EGR, I can't remember if you said you cleaned it or not.. but go with that, and double/triple check vacc leaks,, get the boost gauge
 
for now yes, but I don't see it coming back, I immediately (once I remembered after starting it the first time that I forgot to put one of the vac lines back onto the vibrant vac block lol) noticed much more normal afr at idle and an overall much better sound and smoother feel driving it.. it actually sounded less clogged if that makes any sense
 
So did it slove that check engine light problem? The car engine stalling? Do you think it's the EGR Valve.
 
for me after I reset it the check engine light didn't come on, but I noticed the idle was still pretty bad, I just kept the rpms high enough from dropping and triggering the check engine light to come on, but yes after really really cleaning the EGR valve it works and sounds great, soo much better than before, I would spend a day scrubbing it out with a wire brush (I got 2 for 59c each at lowes, 1/2" they work great, get 2 or 3 b/c the bristles bend easily) and the shop size carb cleaner and just scrub and clean, I let the carb cleaner stuff sit in there over night just because I started it late one night and to get the carb stuff softer off the side.. basicly the end result was I could see the stock walls inside the EGR valve, so it was really clean, and everything is perfect now..

with that said, it is possible that with your symptoms that it's something else, like maybe a bad bpv or maybe a leak somewhere you don't know (the stock vac lines crack really easily, if you plan to do any mods to the car, getting all new vac lines are pretty cheap and are great for knowing the lines you have are not leaking and dried/cracked) but I would definitely clean the EGR valve and go from there
 
I think it may be my bypass valve, how do I check if it works? I checked all the tubes after the intake, no leak no whistling sound. No sound from the other vacuum lines too. My CEL light has been off for 2 days now. I know its gonna come back on. It still would want to stall from high acceleration to neutral. I can control the car when I let it decelerate or not accelerate at all and shift to neutral. Do you think it is the Bypass valve?
 
not sure about the throttle posistion sensor, and my guess for checking the BPV being bad, is.. maybe take the end that is on the hot pipe side and try to blow through it manually, my guess is that you shouldn't be able to get any air through at all, since there is no pressure coming from the vac line connected to it but I am not sure, I would do a search and double check, in the mean time I would really highly suggest cleaning your EGR valve really good, if anything it will help the car, after I cleaned mine the whole car sounded sooo much better and cleaner, but like I said the next thing is I would check the bpv, and I guess search around the forums for a used one if you don't want to spend the money for a forged bpv from PG
 
just by leaking air from the pressurize hot pipe side into the intake side.. it would be like having a vac leak, and especially if after hard shifting it could release more air than it should, although im not 100% sure about how it works but I have heard people with bad bpv that have some of the same issues, but I could be wrong, with this car theres a million things that could be bad with those conditions.. but I would clean the EGR valve and try to find some more information about what a bad bpv would act like.. should be an easy search on advance search "bad bpv" under the msp problem section
 
leex said:
I think it may be my bypass valve, how do I check if it works? I checked all the tubes after the intake, no leak no whistling sound. No sound from the other vacuum lines too. My CEL light has been off for 2 days now. I know its gonna come back on. It still would want to stall from high acceleration to neutral. I can control the car when I let it decelerate or not accelerate at all and shift to neutral. Do you think it is the Bypass valve?
Click to expand...
if it stalls from boost to neutral, thats a characteristic sign of a metered air issue. 100%. your MAF reads the flow and pushes it through the turbo. if its boosting and you blow it off, you lose metered air the ECU assumed was going to the engine, but it never made it and the car stalls. this is why people relocate their MAFS... the vented air was never metered.
if youre running lean though i dont think thats the issue... that causes rich conditions that make you bog till you stall. still - it COULD be AN issue - im beginning to think theres more than one wrong with this car. right before you die are you rich or lean? and when are you lean again? boost or cruise?

leex said:
Unplugged MAF and the car wanted to die, so MAF is working.
Click to expand...
good

leex said:
Could it be throttle position sensor?
Click to expand...
could be, but i would think you would get other symptoms if its your TPS.

ill reread your symptoms, but i think you have some work to get done. if you stall coming out of boost, thats a metered air issue. clean the MAFS, check all your fittings/nipples, try to find an OEM BPV valve on the forums (~$25). other issues would be the EGR, which speedaddiction said helped him, and vacuum leaks, which youre saying youre confident dont exist. i really dont think you need to just throw money at the car needlessly, but you can get "good enough" vacuum line at advance auto for not-that-much, a replacement OEM BPV for not-that-much, MAF and carb cleaner for not-that-much, and do all the work for free. one thing i would do though is tap your brake boost for the BPV when you redo it though. 3/8x3/8x1/8" vac tee.
 
do though is tap your brake boost for the BPV when you redo it though. 3/8x3/8x1/8" vac tee. Can you go more into this? Does the brake boost connect to the BPV?
 
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