Cel - P0171 !!!!!!!!!!!!

[Speed3.5]

Well i recently put on half of AEM CAI , first it was venting to atmosphere and whenever i'd release the throttle RPM would deep as much as it looked like the car would shot off, at some times the battery+some other light would appear and a shake would occur at that time then rpm would go back to ~700.

After 3 days driving like that i managed to reroute BVP to stock position/back to intake. I thought everything would go back to normal but after i punch it and let go the throttle RPM would deep so low it looks like it would shut off and actually so far it stall on me once so far.
After couple of hard pulls on the street , turbo + BVP are much noticeable now, it pulled a CEL - P0171 which definition is : " Fuel trim bank one condition "

Explanation : " The powertrain control moduleuses the oxygen sensor to calculate the air/fuel ratio of the engine. The computer has recognized a rich or lean conditon on one engine bank only. "

Probable Causes :

1- If bank one end two codes set together suspect fuel pressure or MAF Sensor.
2- Oxygen sensor defective.
3- Ignition misfire-repair.
4- Fuel injector problem.

TROUBLESHOOTING P0171 OEM brand: OBD II

"The PCM has determined that during testing, the fuel system for bank 1 was too leen, (Bank 1 identifies the location of cylinder #1, while bank 2 identifies the cylinders on the opposite bank).


What is the best thing to check for , my guess is as good as any but so far i've done this- I've put in Gunk seafome to gas tank- just bc i had it handy.

But the CEL would stay a bit than it would disappear but what bothers me is that it does show after there's a lot of turbo usage( boosting 7 psi often)

 

[slo03.5msp]

vac leak and check the maf. It's a phantom code as far as I'm concerened. Mine trips every 8 months or so. It's always p0171. if you have a boost controller. take it off and hook the vac line back up to the wastegate like its supposed to be and see if it takes longer to trip the code. most likely its the wastegate going out.

 

[FunkyBuddha]

This is the same problem I'm having. it's pissing me off

 

[Speed3.5]

I checked w/ JDM SAM and he said the same "Leak" is the problem except i don't know where it is bc there's so much to check.
I care about the RPM's deeping to low after boost => stop. Thats what pisses me off and when i try to get on WOT on 3rd and sometimes on 4th gear it goes lean sometimes it goes ~15 and just this morning was holding to 11.5 AFR = which i was surpprised but happy to see those AFR and not leaner.

 

[Devilspawn]

I'm having the same problem I think... the first time it came on it threw the same code...the check engine light came on again yesterday

 

[DubbyDoo]

im gettin this code every damn day i drive to autozone and use there obd2 reader and clear it every morning haha and by night time its back on

 

[25FConv]

I got this same code when I started to vent to the atmosphere. I was doing the same this as DubbyDoo. Clearing it everyday and then by the time I start the car up for the second time the CEL would pop right back up. Honestly, I think it is the ECU just relearning the new setup because after about a solid month of it happening it started coming on fewer and fewer times then it just stopped coming on. However, my rpms tend to bounce between 700 and 1000 rpms on a rare occasion but I think that because of the venting and the BOV stays open at idle sometimes.....weird I know but I have been through about 3 sets of internals just to see if it was the internals of the BOV.

 

[DubbyDoo]

oh im gonna get that light to go out i think its my main reason for fuel cut atm

 

[25FConv]

And I concur with your statement DubbyDoo. It did seem like I would hit fuel cut on occasion.

 

[DubbyDoo]

well i cleaned my o2 today no light so far but still get fuel cut, also 25fconv did you get your valve cover from ryan?

 

[25FConv]

Negative haven't seen him, lol eventhough he lives about 5 or 6 blocks away from me. Thanks for sending it with him.

 

[FunkyBuddha]

Replace your coil packs and check for boost leaks. The charge pipe at the bottom of the intercooler sucks..it always comes loose.

Anyways..I fixed my code with 2 new coil packs. Everything runs good now.

 

[magnumP5]

I am now having this reoccurring problem. I first had it come on about four weeks ago after an IM swap but I had that cleared. It came on again about a week later but cleared itself within two days. Now today I go out driving, notice my oil pressure is low so I fill that up and turn on the car to check the pressure and to check for leaks and about two minutes later I notice the CEL sitting there staring back at me. Primary O2 sensory was replaced last Summer, coil pacs have about 50,000 miles on them, spark plugs are less than a year old and I really don't know how old my sparkplug wires are. MAF has also been cleaned and replaced several times. I never had this problem the first year I turbo'd this car so why am I having this issue now?

 

[FunkyBuddha]

Both your o2 sensors are good? Maybe a fried wire? Check your MAF as well to see if it's working. If it's running bad already, and you unplug the MAF, and it gets shittier, it's not the MAF.

Other than that..I dunno what else you'd try. Maybe a clogged cat?

 

[magnumP5]

Both your o2 sensors are good? Maybe a fried wire? Check your MAF as well to see if it's working. If it's running bad already, and you unplug the MAF, and it gets shittier, it's not the MAF.

Other than that..I dunno what else you'd try. Maybe a clogged cat?

I assume both O2 sensors are good because they were both replaced last year. I suppose it could be a fried wire but nothing looks out of the ordinary. The car runs just fine - perfect AFRs in boost and out and at idle which is why I don't think it's actually any of the sensors or fried wires. I cleaned the MAF today but it didn't look dirty at all. Also, I have no cats so it can't be that My next step is to check the spark plugs when it isn't raining. I know you said you replaced the coils and that fixed your problem so maybe that's it? I have noticed that whenever I touch my coils (mostly by accident) when the car is running I will get shocked - should they be doing this (seems like a bad ground) or could this indicate them going bad? I was also told it could be a clogged injector - how could I tell this? My AFRs overall are fine but I supposed one cylinder (as indicated by the CEL) could be running lean.

 

[FunkyBuddha]

With a clogged injector, I'm going to assume that your car will run like s*** and your AFR's will be all over the place.

No, my coils don't shock me when I touch them. The connection from the plug wires to your coils might be loose, or bad.

It's not bad timing as your car would shake constantly.

Only thing I could think of, with limited knowledge, are the:

plug wires
coils
spark plugs

I think I created a thread a while back with kind of similar issues. I posted a pic of what my old plugs looked like. It was bad. LOL

EDIT:

After doing some more reading...I just realized I got this code when I installed a header in my p5 back in the day. I didn't put the Non-fouler trick to the o2 sensor. The code disappears after a few hundred kilometers then comes back. I "fixed" it when I put the Mazda Mp3 ecu in the p5. I heard that the ignition timing is advanced in the mp3 ecu. That could've fixed the CEL code. So..most likely anything ignition wise you should check.

Also leaks in the vacuum or boost side especially near the intake manifold. And don't forget the PCV valve

 

[magnumP5]

Alright so what ties the sparkplugs wires and connections in with the Air/Fuel system? I ask because I just went out and inspected all my spark plugs and they look fine (see pictures below). However, I plugged everything back in nice and snuggly and started the car and poof - no CEL. I thought the only way to get rid of the CEL was to disconnect the battery? Definitely disconnected the MAF this morning and it didn't clear. So is it safe to assume the plugs and/or wires were the culprit?

Sparkplug pictures: left to right is passenger's side to driver's side.

 

[FunkyBuddha]

they look fine.

I know the basic gist of things, but I dont' wanna provide you with wrong information to your question.

basically in point form:

-air comes in pass the MAF
-MAF sees air, tells car to put in xx amount of fuel
-car tells the coil packs to provide xx amount of spark and when (ignition timing)
-exhaust gasses pass out the manifold and cat and passes the O2 sensors
-O2 sensors sees right temperature, sends data back to car
-and repeat

I dunno if this is correct or If I'm missing anything. So depending on what fails, the components of a motor are all related to each other.

So if any of the parts in that system/circuit fail, you will see pretty much the same symptoms, and behaviors. You might get a diff. code for each failing part, but as a general rule, check the parts that are related to each other.

I have a feeling the CEL might come on again so just keep an eye on it. That's what happened to me as well. I put in new plugs, started car, no CEL. Drove it for 10 minutes..CEL came on again. Hope it all works out well.

 

[magnumP5]

^^^ Yeah I know how the whole air/fuel/ignition/metering system works I was just confused as to why, after unplugging only the spark plugs and wires was the CEL cleared when I had other things such as the O2 sensors and MAF disconnected this morning. So far probably about 15-20 miles driven without the CEL coming back. No where near a complete drive cycle but I can't help but be optimistic. I do remember when I first saw the CEL the car was idling at 16:1 but after I blipped the throttle it went back to normal. So far no crazy idle has occurred again but I'm keeping my eyes peeled. I've even done some hard runs to see if everything is alright. The car seems to idle a little better but that is probably just my perception now that the CEL is gone.

 

[FunkyBuddha]

^^^ Yeah I know how the whole air/fuel/ignition/metering system works I was just confused as to why, after unplugging only the spark plugs and wires was the CEL cleared when I had other things such as the O2 sensors and MAF disconnected this morning. So far probably about 15-20 miles driven without the CEL coming back. No where near a complete drive cycle but I can't help but be optimistic. I do remember when I first saw the CEL the car was idling at 16:1 but after I blipped the throttle it went back to normal. So far no crazy idle has occurred again but I'm keeping my eyes peeled. I've even done some hard runs to see if everything is alright. The car seems to idle a little better but that is probably just my perception now that the CEL is gone.

Sweet. Good luck. Maybe it was just some loose connection or something.