Check Engine Light - P1124 and P1126

[GoodJohnny]

OK, I have undergone quite an adventure with my Boxster and wanted to share my experience and results of a viable solution to this problem of Lean Run at Idle. I am trying to be detailed here, so please excuse the length of this post.

First off, I have access to SnapOn Scanner and Emissions Smoke Tester, as well as a facility with multiple vehicle lifts… these did help a lot. Also have Durametric product. All these are definite advantages, the two former more than the latter as my previous laptop was a dinosaur. I WOULD NOT HAVE BEEN ABLE TO DIAGNOSE THIS WITHOUT SMOKE MACHINE.

Symptoms and Codes:
P1124 and P1126 - when the engine detects a lean run condition at idle and enriches the fuel mixture to maximum to compensate.
I also had a verified bad Mass Air Flow Sensor. But that's not really germane to this discussion.
My symptoms were, initially, backfiring through the intake.

Work Done:
It was time to replace the upstream O2 sensors anyway so I did that. The new ones read much faster on the scanner.
I hooked up the smoke machine and first leak was vacuum line from rubber intake boot (bank 2) to fuel pressure regulator. Fixed that.
Then the opposite side rubber intake boot connection and hoses on bank 1 side were leaking. Fixed that.
Changed fuel filter, clogged. Checked fuel pressure, perfect. Checked pressure regulator operation, perfect.
Wasn’t until I had all these leaks fixed that I found Oil Separator leaking. Replaced that and J-tube.
Smoked the care again… smoke poured from spark plug tubes, cylinders 4-6. At this point, I was becoming frustrated. Cylinders 5-6, removed coils and cleaned outer surface with brake clean. Applied neat a uniform coat of black RTV silicone. After setting up, no more smoke there.
Smoked car the last time. Cylinder 4, pouring smoke. The same RTV trick didn’t work. I removed coil and where the sealing rings are on the coil boot, inserted high temp o-rings. This sealed the air leak.

Finally:
I know this is some serious jerry-rigging. But until I reach a magic mileage number or the engine goes poof, not rebuilding this car. It runs far too well and my enrichment readings are acceptable. I have 155,000 miles on this Boxster, 27,000 in the last 11 months. I drive it like it was meant to be driven and have, until now, only performed routine maintenance.

[bar10dah]

Great info. Thanks!

Anyone know of a cheap hobbyist smoke machine/tester? All I see online are commercial ones.

[GoodJohnny]

Originally Posted by bar10dah

Great info. Thanks!

Anyone know of a cheap hobbyist smoke machine/tester? All I see online are commercial ones.

Not that I'm aware. I have the Blue Point one, sold by SnapOn, at my disposal, as well as the coolant refilling device. Excellent tools.

[GoodJohnny]

Little note... Boxster blew front seal out of water pump. One more unto the breach, dear friends
No matter what, I still believe these are the finest automobiles in the world and nothing will alter that

[Bala]

Originally Posted by bar10dah

Great info. Thanks!

Anyone know of a cheap hobbyist smoke machine/tester? All I see online are commercial ones.

I'm planning a bottle of scotch and some cigars with friends if I ever have to do this. Will not spend 1k on a smoke machine!

[bar10dah]

Originally Posted by GoodJohnny

Not that I'm aware. I have the Blue Point one, sold by SnapOn, at my disposal, as well as the coolant refilling device. Excellent tools.

Hmm, maybe it's time to visit with GoodJohnny up in SC. I'll bring my Boxster and a case of beer...

[Bala]

Originally Posted by GoodJohnny

OK, I have undergone quite an adventure with my Boxster and wanted to share my experience and results of a viable solution to this problem of Lean Run at Idle. I am trying to be detailed here, so please excuse the length of this post.

First off, I have access to SnapOn Scanner and Emissions Smoke Tester, as well as a facility with multiple vehicle lifts… these did help a lot. Also have Durametric product. All these are definite advantages, the two former more than the latter as my previous laptop was a dinosaur. I WOULD NOT HAVE BEEN ABLE TO DIAGNOSE THIS WITHOUT SMOKE MACHINE.

Symptoms and Codes:
P1124 and P1126 - when the engine detects a lean run condition at idle and enriches the fuel mixture to maximum to compensate.
I also had a verified bad Mass Air Flow Sensor. But that's not really germane to this discussion.
My symptoms were, initially, backfiring through the intake.

Work Done:
It was time to replace the upstream O2 sensors anyway so I did that. The new ones read much faster on the scanner.
I hooked up the smoke machine and first leak was vacuum line from rubber intake boot (bank 2) to fuel pressure regulator. Fixed that.
Then the opposite side rubber intake boot connection and hoses on bank 1 side were leaking. Fixed that.
Changed fuel filter, clogged. Checked fuel pressure, perfect. Checked pressure regulator operation, perfect.
Wasn’t until I had all these leaks fixed that I found Oil Separator leaking. Replaced that and J-tube.
Smoked the care again… smoke poured from spark plug tubes, cylinders 4-6. At this point, I was becoming frustrated. Cylinders 5-6, removed coils and cleaned outer surface with brake clean. Applied neat a uniform coat of black RTV silicone. After setting up, no more smoke there.
Smoked car the last time. Cylinder 4, pouring smoke. The same RTV trick didn’t work. I removed coil and where the sealing rings are on the coil boot, inserted high temp o-rings. This sealed the air leak.

Finally:
I know this is some serious jerry-rigging. But until I reach a magic mileage number or the engine goes poof, not rebuilding this car. It runs far too well and my enrichment readings are acceptable. I have 155,000 miles on this Boxster, 27,000 in the last 11 months. I drive it like it was meant to be driven and have, until now, only performed routine maintenance.

Nice write up. Thanks.

I replaced my sparkplug tubes+seals, coil tubes, fuel filter, air filter, 2 precat O2s, cleaned throttle body. I did notice my AOS had a little oil. Not sure if it warrants a change but it has ridden for 90k so will be doing it in a couple days. I also noticed my rubber intake boot nipple had a crack. Ordered both sides for replacement. One stupid thing I did was clean the MAF with electronic cleaner. Was a long day and didn't even realize until I drove the next day. Trying to retrace my steps as to why the poor per4formance I found I used the wrong one. Instead of throwing the MAF out I used a qtip with MAF spray and wiped it lightly on the diode and that did the trick.

The car drive like a bat out of hell but my idle goes to 1100 when I come to a stop. I also have P0507-Idle air control system exceeds limit value. I'm attributing this to air leak and specifically to the boots where the vacuum tube connects. Hopefully the replacement will take care of that.

Now a few questions: how did you fix your boot/vacuum line issue. Did you Durametric "Ready status" show fail for any area prior and after the work done?