P0172 CEL fixes
 

This is the third time i fixed my P0172 CEL. Wanted to list the fixes here for the others who might ask for a fix.

Symptoms were all same
- Engine service and traction control off light come up, OBDII reports P0172 (system too rich)
- MAF reading during warm idle is above 3.5
- Rough idle, reduced power, and an overall noisy engine. Especially after the catback, exhaust sound was drony and much louder than normal. Engine is hesitant to rev up.

Fixes
1- The first time fix required just cleaning and reseating the MAF sensor
2- Second time months later was much harder since I had to chase down leaking vacuum lines. The two vacuum lines under the intake manifold connecting to the solenoid, their both ends (i.e. four ends of two lines) needed to be clamped. All of them were completely loose.
3- I fixed this CEL third time yesterday for a completely different reason. Oil catch can was completely full and overflowing. That is PCV not crankcase; crankcase never collects any oil. Cleaning and resetting the CEL fixed the problem immediately.

Hope this helps someone ...

Edit: I have not seen any other CEL and hope this is the last time. But all of the causes were my error as the person servicing my own car.

Thanks! Yes :(

Very helpful info! Thanks for sharing!

Are you still using the stock JRSC filter or did you swap to a dry filter? I’ve heard that helps with the MAF getting dirty?

Yes, i swapped to AEM Dry Flow. There is one model with the exact same size. I had posted the number in JRSC thread

Edit: AEM Dry Flow filter number is 21-2036DK

In case MAF sensor needs to be replaced, I also bought and used Denso 197-6160 sensor as a replacement which works and fits exactly same as the stock MAF sensor but sold for less than half price.

mrg666,

I was wondering if you only ever received the P0172 code or if there were others? I recently received a P0172, C1201, C1241, and B14A1 and, from my research, I am suspicious that the bypass valve provided with the JRSC kit may be at fault, but I am also going to clean the MAF for good measure. I was just wondering if you've had any issues with the bypass valve related to a P0172 code?

Thanks.

I have not seen P0172 because of bypass valve. P0172 means fuel mixture is too rich in other words not enough air. When the bypass valve is not working when the throttle is closed, it just stays closed and causes P0174, lean mixture (not rich) due to too much air at idle (and, of course, the risk of compressor surge). If bypass valve working okay, you should be able to hear the whistle of bypass valve opening with closed throttle. It is also useful to have an OBDII reader to check the MAF value. It should be stable around 2.8-3 at closed throttle and warm idle if MAF sensor is working right and bypass valve is opening.

If you have P0172, fluctuating rpm at idle, and hesitation before revving up, I would clean the MAF sensor first. If it doesn't help, i would check the leaks from air pipes and vacuum hoses.

Thanks for that. Just cleaned my MAF this afternoon, cleared my codes and, things seem to be working correctly again. I did check the evap hoses under the intake manifold and, while the are movable on their spigots, they had not come off to date and I've had the JRSC for about 1,200 miles or so. I'm still going to secure them for piece of mind, but haven't made it a high priority.

Also, I was thinking maybe it was the bypass valve because of this https://www.ft86club.com/forums/show...01#post3088309

Thought I'd contribute my experience to this post. I got the code a couple weeks ago, experiencing the rough idle, hesitation, and notably louder drone at speed. Cleaned the MAF, and the code has not come back since.

Another reason can be faulty MAF extension cable, if used.

@mrg666 - Hi! Did you only clean the PCV valve?

Have also seen this combo:
P0172
P1170
P117B

Found a helpful, related document: http://zatonevkredit.ru/repair_manua...KvrzlLPWuuGJnl