Dr House Part Deux

[Lupo222]

Ok, I'm starting a new thread for this because its reached a whole new level for me.

As some of you know, car was running like dog crap. dropping idle and literally stalling, sputtering and jerking and bucking at cruising speed, regardless of warm or cold.

Threw a P2197 and P0171 code (both o2 sensor related on bank 2 and indicate a lean system).

Bank 2 O2 sensor stays around .001 volts compared to .8- on bank 1. Short term fuel trims stay around .9

Replaced both o2 sensors. still having problems on bank 2.

I did have a wideband installed a few months ago, and it doesn't work. There were wires pulled from under the dash. Not sure if there are any o2 related wires under there that could be lose or damaged?

Also, I replaced the valve covers and the VCT grommets may not be seated properly (i swear they were/are) but a carb cleaner vacuum test reveals no deviations in idle anywhere in the engine bay. Vacuum still reads -12 in at idle.

A/C wasn't blowing strong before but when i replaced the o2 sensors (i disconnected the battery) it got stronger. still not 100% but definitely stronger.

Question:
Do you think its electrical? If so, how do I troubleshoot this? I don't even know where the o2 harness runs.

Any other ideas? I've searched and it seems there aren't really too many threads with my predicament (maybe they just didn't datalog it the way i did?) and it seems the answer for most of them is vacuum, a bad MAF, or something TB/CAI related. If it were MAF/TB/CAI/Vacuum related, would that cause the low volts on just bank 2? Seems electrical...

Oh and if you'd like to see my datalogs, PM me and I'll email them to you. Lito and I are troubleshooting but, as tuning is his job, he's busy with other customers as well, and his diagnosis is check the wiring, something I'm not the least bit comfortable doing w/o someone to guide me, either physically or just walking me through it.

 

[one eyed willy]

Has the tranny been removed for any reason, asking because the 02 sensor wires can get pinched when reinstalling.

 

[Lupo222]

no, a new motor was put in a year or so ago and the car has run fine since then.

 

[one eyed willy]

I would take a look back there, you have some strange things going on and I'd say you have a good chance it is pinched and the wires are just now starting the wear out? It's worth checking, get a small mirror and stick it right behind your blower , and point it down towards the top of the tranny.

 

[Lupo222]

will do. keep the suggestions coming

can we rule out the vacuum leaks/maf issues due to the volts of just one o2 sensor?

 

[one eyed willy]

Do you remember what you did when all the problems started?

 

[Lupo222]

no, not really. i got it tuned, the shop that i rented the dyno from also did the wideband and i had them try to fix it. it got cold and it started acting funny. got progressively worse so i datalogged it and we came to this. total time about 6 months

dyno'd in August, couldn't drive Sept-November (surgery) and it started around late November.

 

[Alfiedagr8]

Give us both long and short term fuel trims as this is the total fuel corrections factor. How many Miles since the work was done? Have u done a compression check and compare bank to bank.


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[Lupo222]

Ill email you over the logs today. The engine swap is a year + old and the dyno/wideband was done in August.

Ill give you a call this evening. Appreciate the time!

 

[chandlern]

Had similar issues with mine idle, stalling, and o2 codes on one bank. It all started after I washed it, went through everything when I got it home and found nothing, went to work for 2 months so I had my buddy drop it off at BBR, after some trouble shooting....fuel filter had a hole in it....

 

[Lupo222]

i just don't know if a fuel filter would cause the volts to that o2 sensor to be that low...or maybe im not understanding the datalog properly

 

[Swarzkopf]

Low O2 sensor volts usually means one of two things:

1. The O2 sensor is bad or the wiring is damaged.
2. The engine is running really lean.

Honestly, my opinion is that step one for you right now is to get the wideband O2 working. On a boosted car, it's probably one of the two most vital diagnostic sensors you have (up there with your knock sensors, in my mind).

Once you get your wideband working, you can look at your actual idle, cruise, and WOT AFR. If your idle is a lot leaner then 14.7, you can basically assume that your factory narrowband O2 sensors are working and you have a fueling issue. If your idle is right at or pretty close to 14.7, you can assume that you have an electrical or other issue with one or both of your factory narrowband O2 sensors.

 

[Lupo222]

narrow band is downstream right? these are the upstream o2 sensors i believe that are faulty. although, it just b2o2 so could that include the narrowband??

^ if thats the case, maybe they put the A/F ratio sensor in the narrowband THINKING it was turned off but lito didn't turn em off? hmmmm

 

[one eyed willy]

all your factory sensors are narrowband.....they only read plus or minus, your wideband would have to be aftermarket and reads from 10-20

 

[Lupo222]

oh ok...so again, do u think the rear one missing could be the culprit in the case that it isn't turned off in the tune??

 

[Swarzkopf]

narrow band is downstream right? these are the upstream o2 sensors i believe that are faulty. although, it just b2o2 so could that include the narrowband??

^ if thats the case, maybe they put the A/F ratio sensor in the narrowband THINKING it was turned off but lito didn't turn em off? hmmmm

Upstream O2 sensors are narrowband O2 sensors that read in volts, between ~100 and 950 or so. They rapidly switch from high (800-900) to low (100-200) at 14.7 (stoich) AFR. This 'switching' indicates proper O2 sensor operation and proper idle and cruiser/light throttle AFR.

The upstream O2 sensors are used by the PCM to 'trim' fueling during idle, cruise, and light throttle where stoich is commanded.

The rear O2 sensors are used to determine if the catalytic converters are functional. While they can influence AFR at start up, generally speaking they do not modify AFR or any other engine run parameters to the extent that the upstream (front) O2 sensors do.

Get the wideband installed. You're honestly wasting time blindly guessing at stuff when you could have a much better picture of what's actually happening with the wideband in place.

 

[chandlern]

Low O2 sensor volts usually means one of two things:

1. The O2 sensor is bad or the wiring is damaged.
2. The engine is running really lean.

Like he said, either o2 issues or she is actually running lean and o2 is doing what its supposed to...in my case the filter was drawing air into the fuel system and leaning out, I wasn't able to tell because it wouldn't run long enough for me to even check the wideband at idle. Though its throwing codes, that doesnt mean its definitely an electrical gremlin that may just be where you're seeing the results of something else. Fuel, air, spark are the basics and since i bought my first mustang those are always the first areas I check when I run into issues. Just my $.02

 

[ummduh]

will do. keep the suggestions coming

can we rule out the vacuum leaks/maf issues due to the volts of just one o2 sensor?

No, you could easily have one bank of the engine leaking vacuum due to say a mis-seated intake or blown out gaskets(among others), and the other bank could be just fine.

 

[Lupo222]

well it appears that the wiring from the sensor back to the pcm is bad...the sensor is getting proper voltage. they're gonna check the wiring back and i may need a new pcm. any advice on buying one?

 

[one eyed willy]

Did you ever look at the top of the tranny to see if the wires were pinched there?