speedtrapped

Another code! No bashing, just looking for help
I got car back from protosport last Friday, and John was awesome. I was chasing p1126/28 codes, as threads I have posted stated this is everything done to the car in last 600 miles:
New MAF
New plugs
New 997 coil packs
New oil cap seal
Vac leaks none
Exhaust leak found and repaired
Pressure tested, passed.
John was second mechanic on car, had her for week, drove her over 100 miles, and I drove her 60 up there and 60 back(I had taken picture of scan, and CEL light- but cleared codes. John was scratching head...the p1126/28 never came back. I drove the car another 300 miles since, today on way home idle skipped a little 5 miles after startup CEL....durametric scan, p1133 Porsche fault code 358!!!
2 things, car drives awesome, and strong...I am not posting to bash, just looking for some input.
Iirc macster suggested on renn list to replace O2's when I listed what was
done and codes kept coming back.
Any ideas? I just want own her for a solid month w/o a code.
Tia

911SLOW

P1133

358 Oxygen Sensing Adaptation, Lower Load Range,
Bank 2 - Below Limit

Diagnosis conditions
• Oxygen sensing system active
• Time elapsed after engine start-up: 250 to 350 seconds (USA)
• Time elapsed after engine start-up: 302 to 402 seconds (RoW)
• Engine temperature greater than 60 °C

Possible fault cause
♦ Incorrect signal from MAF sensor
♦ Fuel pressure too high
♦ Fuel injector leaking


Check:

1 Check signal from MAF sensor
♦ Connect special tool 9637 Measure voltage at pin III/23 and ground. Switch on the ignition. The correct reading should be 0.9 to 1.1 V
♦ Start the engine approx. The correct reading should be 1.4 V. If not, replace MAF sensor.

2 Check fuel pressure

3 Check fuel pressure regulator, vacuum connection and fuel return line.
correct pressure 0.4 - 0.6 bar

4 Check fuel injectors for leaks




358 Oxygen Sensing Adaptation, Lower Load Range,
Bank 2 - Above Limit

Diagnosis conditions
• Oxygen sensing system active
• Time elapsed after engine start-up: 250 to 350 seconds (USA)
• Time elapsed after engine start-up: 302 to 402 seconds (RoW)
• Engine temperature greater than 60 °C


Possible fault cause
♦ Incorrect signal from MAF sensor
♦ Intake air system leaking
♦ Fuel pressure too low
♦ Volume supply of fuel pump too low
♦ Fuel injectors fouled

Check:

1 Check signal from MAF sensor
♦ Connect special tool 9637 Measure voltage at pin III/23 and ground. Switch on the ignition. The correct reading should be 0.9 to 1.1 V
♦ Start the engine approx. The correct reading should be 1.4 V. If not, replace MAF sensor.

2 Check exhaust system for leaks

3 Check for air leaks in intake air system

4 Check fuel pressure

5 Check volume supply of fuel pump

6 Fuel injectors fouled only If preceding Check Points were
negative, the fuel injectors may be fouled
♦ Clean fuel injectors (ultrasonic cleaning device) or replace them

speedtrapped

ok, that's pretty comprehensive...the MAF has only 600 miles on it....the exhaust leak was found and fixed. I will check fuel pressure, maybe the split hose? Ty for the information.

Macster

I haven't gone back and looked at the older thread, but I do not think I would have recommended replacing the O2 sensors. The error codes P1126/P1128 do not point to O2 sensors but to intake system leaking, fuel pressure too low, fuel injectors contaminated, or volume supply of the fuel pump too low.

911SLOW posted a comprehensive list of things to dig into regarding the current error code and I have nothing to add to that.

Sincerely,

Macster.

speedtrapped

Macster, sorry for this miss quote...it was wross996tt. either way, I either blew a MAF 600 miles in(I do have the EVOM box with a new oilless paper filter), both JA Autowerks and John from protosport, checked vac lines, pressure tested, even exhaust leak fixed. chase, chase chase...thankfully car runs great it seems to happen only on cold start, at least the last 3x i got CEL, happened right after cold start up

Macster

One thing that comes to mind -- it is a long shot -- is that the aftermarket air filter/air box (even if the filter is oil-less) may result in turbulent air flow past the MAF and as a result the MAF comes up with analog/digital nonsense.

I do know not what is involved, but you might consider going back to the stock air filter/air box and see if the behavior appears.

Sincerely,

Macster.

speedtrapped

Funny u mention, John and Todd knighton think the evom screws up the MAF. Yes, I had an ad for wtb, so I will keep looking for a stock box. I tried logging MAF tonight, but there are 3 dif MAF values. I think the hot film one is the relevant one? Also, what is appropriate reading?, idle? 2k,3k,4k,5k.... I need to find open road, and do a 3rd gear wot pull for log and post.

wross996tt

Actually this is my quote Although you neglected to communicate all of your "upgrades". It is always difficult to diagnose when the poster only tells part of the story. I suggest losing the EVOMs air box. I blew 3 MAFs in a week until I switched that box out FWIW.

speedtrapped

thanks for input guys. Still looking for stock 996tt air box, to swap out EVOM

Macster

Sorry, but all I've had to view is the OBD2 MAF reading which is grams of air per second. (A 16-bit value with each bit worth 0.01 g/s. 65535 = 655.35 g/s)

What I was told to look at is the adaptation values, the short term (and long term) fuel trims.

The problem with the trims is as I vaguely remember it -- it has been some time since I had any need to look at these -- is they (the short term trims anyhow) can appear a bit goofy and by goofy I mean varying quite a bit -- normally.

For instance clearing the error codes (which resets the long term trims to their defaults (0)) and then starting the engine and looking at the short term trims one sees the short term trims going 'rail to rail' (nearly +10% to -10% (anything more can trigger a CEL) as the DME seeks to relearn the ideal fueling which then gets transferred into the long term fuel trims.

I have only had one MAF go bad and I do not recall now how I confirmed this was bad. It involved -- IIRC -- monitoring both the MAF reading and the short term trims.

After typing the above, I seem to recall a clue the MAF was suspect was while the air flow reading remained rather reasonable, the short term trims were all over the map, so to speak. The adaptation values supplied by the MAF/DME based on a failing MAF were wrong and wrong not in a flat line sense but just goofy wrong. I do not recall now if I tried disconnecting the MAF but I do recall remembering I had the original MAF set aside (which was replaced when I misdiagnosed it as being bad when in fact the real problem turned out to be an oil filler tube cap leak problem) and I used this to replace the suspected MAF.

Fortunately for me the original MAF not only worked but that the symptoms went away (and have remained away now for 70K or more miles) confirmed the MAF was bad.

Sincerely,

Macster.