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

[JFP in PA]

Originally Posted by porschefan76

First, thank you both for responding so soon.



P1126 is the only code I get legitimately. When I ran with MAF disconnected I got some codes for the MAF, but not since reconnecting. Also have not gotten P1126 back since first time. No additional pending codes.



Great, as soon as it gets warm enough to mess with the plastic window, I'll pull the fuel rail and look at the injectors as I change them.

I guess Durametric tool does not divide further because I do not see FRAU or FRA0.

RKAT values of -2.4 indicates rich at idle and FRA 1.3 (positive) is lean above idle then correct? I was considering smoking the intake again but if it's over-rich at idle, likely unwarranted?

Anything else I should be checking? Thank you for your time!!

You may be seeing a lean situation because the one or more injectors are carboned up and not delivering a full pulse fuel volume.

[porschefan76]

Originally Posted by JFP in PA

You may be seeing a lean situation because the one or more injectors are carboned up and not delivering a full pulse fuel volume.

OK, this is kind of where I was going when I ordered the replacement fuel injectors, so hopefully, I get some progress there.

One more question, the -8.2 bank 1 camshaft deviation alone should not be enough to cause these hesitation issues etc, should they?

Thank you again.

[blue62]

Following your issue with interest.
Please post results once you have changed out the injectors.

[porschefan76]

Originally Posted by blue62

Following your issue with interest.
Please post results once you have changed out the injectors.

Will do. Thank you for your interest and help!

It looks like I might be able to get the top in to service mode this weekend, so hoping to get to the fuel injectors.

[Zzorro]

Originally Posted by blue62

Following your issue with interest.
Please post results once you have changed out the injectors.

Likewise.

My codes are clear after changing out all 4 O2 sensors, but still get lingering short periods of bogging, or lack of power. Have never stalled.

[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

[porschefan76]

Wow, this community is awesome. Thank you all for continuing to follow along and helping. I've currently got my heater running in my garage trying to break it into the 50's so I can get some work done today.

Originally Posted by Zzorro

Likewise.

My codes are clear after changing out all 4 O2 sensors, but still get lingering short periods of bogging, or lack of power. Have never stalled.

I've got my Durametric data and it appears that my pre-cat O2 sensors are working as intended. I'm fairly certain my post-cat are working properly as well, as they maintain a steady mV reading at idle, but they do change as the revs change. So, I haven't considered changing those yet, but might be something I'll do if it's recommended. Again, I've got my data and plots if anyone wants to dig in, but this is not my profession, so I only know what I've read about this data/plots.

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

I actually make reference to your video in my OP. They were very helpful and helped clarify things when I checked for fuel pump volume and fuel regulator pressure checks, so thank you! I was really hoping my problem was fuel pressure as it has a tendency to backfire into the intake and lope similar to your car in the video when it's cold, but not when warmed up.

I'm really hoping replacing the fuel injectors gives some results, because after that, I'm not even sure which animal to chase next. As I mentioned above, my bank 1 camshaft deviation is out of spec, but not enough to throw a code, so I am not sure if that is contributing to the issue or not.

[porschefan76]

Hello all, just an update. I was able to get the temp up in the garage and got to work. The P1126 CEL that started all of this was for bank 2, so I started there. It took a little longer than I anticipated, so I only got bank 2 fuel injectors replaced. I'll do bank 1 when I get some warm weather again.

Unfortunately, there was no real change to the idle/throttle condition. Upon first start the engine still responds very poorly to throttle input. Backing down the driveway, response improves slightly, but not much. I left the engine top cover off for the first 5 minute drive so I could monitor for leaking fuel at stop signs. With that cover off, I can clearly hear swooshing noises when I crack the throttle, especially on blips. At one point, when I was first pulling away from the driveway, I could even hear a whistling noise, so I'm convinced this must be a vacuum leak. Another run at the intake smoker when the weather gets warmer.

Anyway, in frustration, I took a quick (and annoyingly shaky) video with my phone to listen to in an attempt to locate the noise. It appears to me to be coming from the vicinity of the throttle body. I've decided to upload the video and post a link in this thread in case anyone wanted to take a listen and see if it sparks any thoughts on further troubleshooting.

(truly sorry for how bad this video is. I might make a more patient attempt soon)

I think I may get a unidirectional microphone I can move around the engine and listen while a buddy hits the throttle as well, to see if i can really narrow it down. I have avoided using the "spray carb cleaner" step the whole time, but I might do that tomorrow in the area where the infamous J-tube connects to the plenum.

So, I guess right now, my question to you folks is, "Do you think the sounds in the video I linked indicate a vacuum leak?" Please feel free to let me know what it could be if it does not sound like a vacuum leak as well. As usual, thank you for your time!

[blue62]

you have a interesting situation there.
Backfiring into the intake would indicate a vacuum leak
The sound in your video sounds somewhat like a vacuum leak.
But on the other hand your low RPM fuel trims (RKAT) are negative values indicating a rich condition at idle. Vacuum leaks cause lean conditions at idle. Your mid to upper range fuel trims look to be positive values which you would expect under load at mid to upper RPM range. Adding fuel under increased engine load.
Porsche and or Durametric expresses fuel trims in a manner that I am not very familiar with so I could be off on what I think I see.

What are your pre cat o2 sensors doing at idle and again at say 3000 RPM???
If fuel trims are going negative at low RPM I would expect the O2 sensors to be showing a rich condition. Voltage above .500 mil volts then dropping as RPM increases and fuel trims go positive.
The sound in your video also (to me) sounds a little like a possible exhaust restriction.
Any chance the Cats are plugging up??

Don't know if I have helped or added confusion
But those are my thoughts