P1126 and low rpm hesitation - all troubleshooting listed- Help greatly appreciated! - 986 Forum - The Community for Porsche Boxster & Cayman Owners

ike84 · 02-25-2021, 11:35 AM

Hey fan, glad to hear you're making progress. I could be wrong but I think that p1126 is a lean condition? Your negative fuel trim would support that. If you've got new injectors and good pressure then I would suspect a small leak. I know you said you smoked it but as we all know small leaks can be a pita for even the best to find.

Somebody else chime in on this, I don't wanna steer you wrong.

Sent from my POCOPHONE F1 using Tapatalk

blue62 · 02-25-2021, 01:13 PM

Porschefan: Have you looked at the freeze frame info when the p1126 code triggers???
Could be a clue in that info.
I know you have smoke tested it and that the code is for just the one bank but the p1126 code is most often associated with some form of vacuum leak!!

blue62 · 02-25-2021, 01:31 PM

Quote:

Originally Posted by ike84

Hey fan, glad to hear you're making progress. I could be wrong but I think that p1126 is a lean condition? Your negative fuel trim would support that. If you've got new injectors and good pressure then I would suspect a small leak. I know you said you smoked it but as we all know small leaks can be a pita for even the best to find.

Somebody else chime in on this, I don't wanna steer you wrong.

Sent from my POCOPHONE F1 using Tapatalk

Yes a vacuum leak of some sort has been my thought from the beginning.
Faulty injectors, Faulty O2 sensors, Or a Faulty MAF sensor can all cause a lean situation.
Porschefan has replaced or proven all those things good so I am still betting on a vacuum leak of some kind.

porschefan76 · 02-25-2021, 02:27 PM

Quote:

Originally Posted by blue62

Yes a vacuum leak of some sort has been my thought from the beginning.
Faulty injectors, Faulty O2 sensors, Or a Faulty MAF sensor can all cause a lean situation.
Porschefan has replaced or proven all those things good so I am still betting on a vacuum leak of some kind.

I am truly hoping this turns out to be vacuum! I will get that smoke machine back on the intake ASAP (weather/plastic window ugg). Thanks again!

Gilles · 02-25-2021, 03:41 PM

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

porschefan76 · 02-25-2021, 04:48 PM

Quote:

Originally Posted by Gilles

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

Hi Gilles. Having just replaced all of my fuel injectors, on the fuel rail side, I think you'd have a fuel leak (pressurized fuel rail). On the intake manifold side, I suppose you would have an vacuum leak, yes.

If you have to replace your injectors or o-rings, I used a small amount of the recommended white lithium grease on all of the o-rings and it really made everything go back together nicely and prevents the o-rings from twisting upon insertion. Thanks!

Gilles · 02-25-2021, 06:13 PM

Thanks for the tip!

porschefan76 · 02-26-2021, 07:16 AM

Quote:

Originally Posted by Gilles

Thanks for the tip!

No problem! Good luck! Bank 1 injectors are worlds easier to replace than Bank 2 due to tight working quarters with respect to the fuel return line nut.

porschefan76 · 02-25-2021, 02:25 PM

Quote:

Originally Posted by ike84

Hey fan, glad to hear you're making progress. I could be wrong but I think that p1126 is a lean condition? Your negative fuel trim would support that. If you've got new injectors and good pressure then I would suspect a small leak. I know you said you smoked it but as we all know small leaks can be a pita for even the best to find.

Somebody else chime in on this, I don't wanna steer you wrong.

Sent from my POCOPHONE F1 using Tapatalk

Hey Ike! Thanks for following up! Yes, I've had some progress, and it's driving much better, thankfully. I finally experienced those "smiles per gallon" again yesterday. I did notice a SLIGHT hesitation coming back on the gas in third gear yesterday while being slightly aggressive on an empty stretch and corner, but otherwise much improved.

I am honestly not sure one way or the other if it a lean or rich code. I have this excerpt from the Porsche/Bosch DME code list:

Quote:

In above, being "below limit" can go one of two ways in my mind. If it's referring to the fuel trim being below limit, that would indicate a rich condition to me, because fuel trim would be subtracting from the injector time. If it's an O2 sensor that is below limit, to me that means lean because below .45mV is lean and above .45 mV is rich, unless I've got that reversed. The fact that Banks 1&2 RKAT are negative seems to support rich at idle to me as well, as RKAT is "range 1" so far as I can tell, which includes idle.

Other news and updates, I just had some warm temps in the garage, so I vacuum tested the power brake booster line and it held vacuum. I also started the car, pulled the vacuum hose from the fuel pressure regulator (rpms surged) and pulled about 10 psi of vacuum (over Porsche specification, I wonder if this means anything?). So the intake vacuum appears intact, if not high. That said, once outdoor temps are above 55F, I'll be smoking the intake again to look for leaks.

Anyway, if anything jumps out at anyone, please let me know. I need some next troubleshooting steps.