P1126 and low rpm hesitation - all troubleshooting listed- Help greatly appreciated!

[porschefan76]

Hello all! I think I have some positive news. I want to thank each and every person who chimed in with ideas and helped me through this. I pulled a few posts that I'll quote below, and then get on with what's new!

Post #3

Originally Posted by JFP in PA

I'd start pulling the fuel injectors, looking at the tips for carbon fouling.

RKAT is the adaptation value near idle.
FRA is the adaptation value under load and further divided into FRAU (lower load range ) and FRAO (higher load range) ranges (perhaps the durametric doesn't display these divisions).

The RKAT values near idle are used to change the length of the injector pulse to account for deviations from ideality (ie intake leaks) to maintain the proper O2 sensor reading. The RKAT value is an additive factor and can deviate by +/- 4.5%. The FRA value is a multiplicative factor and can deviate by 1.32 to 0.70. The positive values or values greater than 1 increase the injector pulse length to account for a lean mixture, and negative values and values less than 1 are to compensate for a rich mixture.

Post #10

Originally Posted by Brian Minson

I had a 2001 986 as well with the same issue and ran thru all those fixes as well. Have you REPLACED the MAF?? Just an idea.

Here is the 986 DIY playlist of videos I did on my car's issues.

https://www.youtube.com/playlist?list=PLbBMHPz04qDW2lbqUZ4p2yWK9joftSOEO

Brian
HTTP://986Brotherhood.com

Post #31

Originally Posted by blue62

Agree your P1126 is another issue.
Perhaps some form of vacuum leak.
Or MAF sensor but there are ways to test it.

Post #57

Originally Posted by ike84

I just realized that I said something that doesn't make sense and I am now far more confused. 1126 is lean, but negative fuel trim is the car pulling fuel out. I typed that earlier in a rush and didn't realize what I had said.

But that was the original reason I recommended changing the o2 sensors in the first place - things are pointing to a lean condition but the sensors are reading rich and hence the ecu is pulling fuel.

I'm not sure I'm helping at this point lol. This seems really screwy to me though and I'm not sure I can explain it any further at this point. Sorry dude . I would still check for leaks if you've had every off recently but the continued 1126 when sensors are detecting rich and pulling fuel back has got me thoroughly confused.

Sent from my POCOPHONE F1 using Tapatalk

Post #53

Originally Posted by Gilles

just curious, could a Dry fuel injector Seal could cause a vacuum leak..?
.

OK, so the one thing I have not done since replacing the fuel injectors (first BIG change) was unplug the MAF and see what happens. I know, major oversight on my part in retrospect, right?

I found 3 posts of people with P0107 & P1126 at the same time. In all three cases, a new MAF ended up being the fix. So, I unplugged the MAF this morning. Bank 1 & 2 RKAT 0.0 and FRA 0.99 (I don't think they adapt without a MAF) and O2 sensors looking good the whole test drive, she drove like a bat out of hell and wailed like a banshee the way I remembered. Intake funkiness on throttle is gone and oddly enough, some top end noises (valves, chains?) that had me guessing disappeared as well. I've got a new MAF on order and it'll be here Saturday.

So, what I *think* happened was a combination of things. I think I had a leaking bottom o-ring and/or fouling on one of the Bank 1 fuel injectors, because all of the sputtering and intake back firing ceased after they were replaced. I also think I had a failed MAF due to the K&N air filter that I had been meaning to replace but didn't until I had issues. The bad injector had the car sputtering and popping and the bad MAF had us chasing our tail on rich at idle.

I unplugged the MAF before changing the fuel injectors, so I didn't get any change because of injector issues and after changing the injectors, because my MAF appeared to be functioning in Durametric, I never took it back out of the loop.

I will report back on Saturday after I drive it and capture data with the new MAF in, but I'm cautiously optimistic. Regarding the P0107, the ambient pressure sensor is reporting 1010 hPa in Durametric, which corresponds with 1 bar, so that looks to be functioning properly. Right now, the car has codes P0102 and a code for intake air temperature sensor (both are MAF codes, as expected). At the end of the day, I think the only parts changed prematurely may have been the upstream Bosch O2 sensors, but at like $40 each, I will not be complaining!!!

A very sincere thank you again to all of you!!

[ike84]

Originally Posted by porschefan76

Hello all! I think I have some positive news. I want to thank each and every person who chimed in with ideas and helped me through this. I pulled a few posts that I'll quote below, and then get on with what's new!

Post #3


Post #10



Post #31



Post #57



Post #53



OK, so the one thing I have not done since replacing the fuel injectors (first BIG change) was unplug the MAF and see what happens. I know, major oversight on my part in retrospect, right?

I found 3 posts of people with P0107 & P1126 at the same time. In all three cases, a new MAF ended up being the fix. So, I unplugged the MAF this morning. Bank 1 & 2 RKAT 0.0 and FRA 0.99 (I don't think they adapt without a MAF) and O2 sensors looking good the whole test drive, she drove like a bat of hell and wailed like a banshee the way I remembered. Intake funkiness on throttle is gone and oddly enough, some top end noises (valves, chains?) that had me guessing disappeared as well. I've got a new MAF on order and it'll be here Saturday.

So, what I *think* happened was a combination of things. I think I had a leaking bottom o-ring and/or fouling on one of the Bank 1 fuel injectors, because all of the sputtering and intake back firing ceased after they were replaced. I also think I had a failed MAF due to the K&N air filter that I had been meaning to replace but didn't until I had issues. The bad injector had the car sputtering and popping and the bad MAF had us chasing our tail on rich at idle.

I unplugged the MAF before changing the fuel injectors, so I didn't get any change because of injector issues and after changing the injectors, because my MAF appeared to be functioning in Durametric, I never took it back out of the loop.

I will report back on Saturday after I drive it and capture data with the new MAF in, but I'm cautiously optimistic. Regarding the P0107, the ambient pressure sensor is reporting 1010 hPa in Durametric, which corresponds with 1 bar, so that looks to be functioning properly. Right now, the car has codes P0102 and a code for intake air temperature sensor (both are MAF codes, as expected). At the end of the day, I think the only parts changed prematurely may have been the upstream Bosch O2 sensors, but at like $40 each, I will not be complaining!!!

A very sincere thank you again to all of you!!

If you're ever in the lake cumberland area I owe ya a beer!

Congrats on (hopefully) getting it figured out. Let us know what happens!

Sent from my POCOPHONE F1 using Tapatalk

[porschefan76]

Originally Posted by ike84

If you're ever in the lake cumberland area I owe ya a beer!

Congrats on (hopefully) getting it figured out. Let us know what happens!

Sent from my POCOPHONE F1 using Tapatalk

Hey Ike! Haha, if I'm ever in the Lake Cumberland area, I OWE YOU A BEER!

Will post update as soon as the new MAF is in!

[blue62]

Originally Posted by porschefan76

Hello all! I think I have some positive news. I want to thank each and every person who chimed in with ideas and helped me through this. I pulled a few posts that I'll quote below, and then get on with what's new!

Post #3


Post #10



Post #31



Post #57



Post #53



OK, so the one thing I have not done since replacing the fuel injectors (first BIG change) was unplug the MAF and see what happens. I know, major oversight on my part in retrospect, right?

I found 3 posts of people with P0107 & P1126 at the same time. In all three cases, a new MAF ended up being the fix. So, I unplugged the MAF this morning. Bank 1 & 2 RKAT 0.0 and FRA 0.99 (I don't think they adapt without a MAF) and O2 sensors looking good the whole test drive, she drove like a bat of hell and wailed like a banshee the way I remembered. Intake funkiness on throttle is gone and oddly enough, some top end noises (valves, chains?) that had me guessing disappeared as well. I've got a new MAF on order and it'll be here Saturday.

So, what I *think* happened was a combination of things. I think I had a leaking bottom o-ring and/or fouling on one of the Bank 1 fuel injectors, because all of the sputtering and intake back firing ceased after they were replaced. I also think I had a failed MAF due to the K&N air filter that I had been meaning to replace but didn't until I had issues. The bad injector had the car sputtering and popping and the bad MAF had us chasing our tail on rich at idle.

I unplugged the MAF before changing the fuel injectors, so I didn't get any change because of injector issues and after changing the injectors, because my MAF appeared to be functioning in Durametric, I never took it back out of the loop.

I will report back on Saturday after I drive it and capture data with the new MAF in, but I'm cautiously optimistic. Regarding the P0107, the ambient pressure sensor is reporting 1010 hPa in Durametric, which corresponds with 1 bar, so that looks to be functioning properly. Right now, the car has codes P0102 and a code for intake air temperature sensor (both are MAF codes, as expected). At the end of the day, I think the only parts changed prematurely may have been the upstream Bosch O2 sensors, but at like $40 each, I will not be complaining!!!

A very sincere thank you again to all of you!!

My understanding of unplugging the MAF sensor is that the DME reverts to a default fuel map in open loop mode so there is no closed loop type fuel correction.
Also this default fuel map is on the rich side so if you have a vacuum leak and you unplug the MAF the car tends to run very well. Not to say your issue is not MAF related could very well be. Will be interesting to hear the outcome after you install the new MAF. I hope you ordered a Bosch MAF these cars don't seem to do well on after market MAF sensors.
Also if your running a K&N filter that is the oil type they destroy MAF sensors

[porschefan76]

Originally Posted by blue62

My understanding of unplugging the MAF sensor is that the DME reverts to a default fuel map in open loop mode so there is no closed loop type fuel correction.
Also this default fuel map is on the rich side so if you have a vacuum leak and you unplug the MAF the car tends to run very well. Not to say your issue is not MAF related could very well be. Will be interesting to hear the outcome after you install the new MAF. I hope you ordered a Bosch MAF these cars don't seem to do well on after market MAF sensors.
Also if your running a K&N filter that is the oil type they destroy MAF sensors

Hey blue62! Yes, I agree, although I'm not sure it's running rich, as the RKAT is 0.0 and the FRA .99 and STFT look like they're operating properly going +/- 5% throughout the test drive. I'm really hoping it's the MAF as the negative RKAT values (rich at idle) just don't make sense and I have taken each vacuum hose off of the reservoir and tested with my hand pump and they've passed. I've still yet to fully test the EVAP system (vacuum etc) but the Evap Valve under the bank 2 air intake appears to be functioning properly. Beyond that though, no testing has been completed on fuel canister/hoses etc. I'll post as soon as I get the new MAF in and a test drive/data.

EDIT: Forgot to mention, yes, it's the Bosch replacement MAF and the K&N filter is in a landfill somewhere these days. Replaced with OEM air filter.

[porschefan76]

Ok, I think I'm going to call this the end for now. I installed the new MAF sensor and took a test drive. Wow, what a difference, driving much better than without the MAF. I did not reset the codes (P0102 and P0112, both for MAF) as I was thinking they'll reset themselves after a couple of drive cycles like other codes. Is this true for the MAF codes or should I just reset them?

I took some data samples as well. Bank 1 RKAT is -0.17 & FRA is 1.00. Bank 2 RKAT is -0.20 and FRA is also 1.00. O2 sensors all looked like they were doing their thing! Very excited, but I only did roughly 20 mile test drive tonight because:



Out of the frying pan and into the fire HAHA It doesn't look like it's been leaking for long, and it is a very small leak. I got my borescope out and I think it's a crack in the tank at the usual spot underneath:



Sorry about the poor focus but it's essentially a point-and-shoot 1080p borescope. Tank, cap & sending unit are ordered and should be arriving mid-week, so I guess that's the next project for now. Once that's replaced, I'll put some miles on the car with the new MAF and verify I do not get the codes back. I'll post back after a few hundred miles. Thanks all for all of the help!