Do 1126, 1128 and 1130 codes mean rich or lean?

[Dale_K]

My 2000 S Tiptronic lit the CEL a couple of weeks ago with the 1126 code. I looked over the engine and found a leaking oil fill tube and got it replaced at a local independent shop. The CEL came back on today after about 200 miles with 1126, 1128 and 1130 showing in my generic scanner.

Do those codes mean the motor is running rich or mean it's running lean? I'm a little confused because I've read some stuff that says it means it's running rich but everybody seems to give advice to check for vacuum leaks and that wouldn't make it run rich - just the opposite.

I don't hear any leaks after the oil fill tube was replaced. Before I could wiggle the tube around and hear a definite leak, now the replacement tube is mounted more solidly and no hissing. But if the codes mean the car is running rich I'm fighting a losing battle looking for intake leaks.

Assuming the MAF and O2 sensors are working OK, what could make the car run rich? The only things I could think of would be too much fuel pressure and (more farfetched) something in the fuel tank vent system that is feeding the intake gas vapors when it's not supposed to.

What's the best strategy... put on a new MAF and hope?

[RFM]

Here we go, the DME has reached its RICH threshold value (can NOT be MORE enriching) for both cylinder banks, which means that the engine runs TOO LEAN !!! Air leaks or MAF are plausible causes.

[Dale_K]

Thanks. The terminology can be confusing. Running rich vs can't enrich any further. The car's exhaust actually smells a little rich when I'm near it at idle although I know you can't really depend on smell (could be a clue though). Maybe I can find somebody with an exhaust gas analyzer. Then if the gas analyzer says rich while the car is saying it wants even more enrichment I guess that would point to the MAF or something else in the control/feedback loop.

I hate to throw parts at problems unless they're cheap parts.

[hucqym]

I am in the same boat as you (just P1133 also). The trouble is that my '01 boxster also wont start so doesnt give me a way to check further for leaks.

When you guys talk about oil filler tube leaks, are you really referring to the hard plastic tube located in the trunk? The only way I see that could leak is if it is cracked or the cap/seal isnt good. Both look good on mine.

The last time my engine was running, i could feel suction with the cap off so there does seem to be a leak somewhere.

Now if you are referring to the oil filler hose between this plastic tube and the lower hose going to the engine block or the PN- 996-107-254-03, then I find it hard to uninstall. The connection to the lower hose is fine but the connection to the filler tube is PITA. Cant reach from the top to the spring clamp nor does it look accessible from the wheel bay (havent tried). How do you guys do it?

[Dale_K]

I had a local shop replace the oil fill tube segment you mention. They charged me over $300 so maybe I should have attempted it myself. Sears sells hose clamp pliers that might work. They have a cable connected to the handle so you don't need to get the entire tool near the clamp. It cost $40 at my local Sears store. I don't know if a really bad leak in the accordian section will prevent the car from starting. Maybe you could cap off that section near the throttle body and temporarily eliminate the pipe for diagnostic purposes.

I ordered the Durametric ODB cable and software yesterday. I'll take some measurements of the existing MAF sensor readings and start a new thread to see if they look wrong. Too bad there's no way to temporarily test a known good MAF sensor and compare it to my old one. I also ordered the ODBII Porsche repair manual so that I can better understand the theory of operation and repair stategies. My luck will be that I'll buy a new $300 MAF sensor only to find out it produces the same results as my old one. But at least I will know that answer through actual measurement through the Durametric rather than guesswork.

Looking at the Porsche service manual yesterday I see there is a fitting on the fuel rail to connect a pressure gauge. Low fuel pressure could produce the same symptoms (DME trying to enrich beyond its maximum limit). I haven't looked into how much a fuel pressure testing gauge cost. The manual also says the cap for the fitting on the fuel rail must be replaced if you take it off and I don't have a new one.

[kbrandsma]

My 2000 S Tiptronic lit the CEL a couple of weeks ago with the 1126 code. I looked over the engine and found a leaking oil fill tube and got it replaced at a local independent shop. The CEL came back on today after about 200 miles with 1126, 1128 and 1130 showing in my generic scanner.

Do those codes mean the motor is running rich or mean it's running lean? I'm a little confused because I've read some stuff that says it means it's running rich but everybody seems to give advice to check for vacuum leaks and that wouldn't make it run rich - just the opposite.

I don't hear any leaks after the oil fill tube was replaced. Before I could wiggle the tube around and hear a definite leak, now the replacement tube is mounted more solidly and no hissing. But if the codes mean the car is running rich I'm fighting a losing battle looking for intake leaks.

Assuming the MAF and O2 sensors are working OK, what could make the car run rich? The only things I could think of would be too much fuel pressure and (more farfetched) something in the fuel tank vent system that is feeding the intake gas vapors when it's not supposed to.

What's the best strategy... put on a new MAF and hope?

I had 1128 and 1130 and replaced the MAF. That's about $200. I would conclude that is most likely the problem before replacing. What are your symptoms? Maybe clean the MAF first. How many miles? Mine was 100K before MAF went bad and the engine sputtered at about 5K usually in third gear. I found a good price at Autohaus for under $200 shipped at the suggestion of a "Contributing Member" on this Board.

Edited March 22, 2011 by kbrandsma

[Dale_K]

My car (103k miles 2000 S Tip) seems to be running perfectly. It runs very smoothly with no misfires at any rpm or load and has full power. Yet it continues to bring on the CEL with the running lean codes. Yes it very well could be the MAF sensor. I only wish there was some kind of test available to verify the accuracy of the old MAF sensor before spending the money. Not only because of the money but because true diagnostics appeals to me in kind of a scientific method approach.

I talked to the independent repair shop who did the oil fill tube replacement and asked their advice. They are willing to install a MAF sensor and allow me to return it and get my money back if the CEL comes back. It's kind of hard to turn that down, even though I could do the work myself pretty easily. I've already attempted cleaning with genuine MAF sensor cleaner.

I ordered the Durametric unit and the Porsche ODBII manual and should get them in a week or so. My plan is to obtain actual MAF sensor readings at idle, 1,000 2,000 and 3,000 rpm on the old sensor and compare them to the new sensor. This is actually going to cost me more than simply replacing the part based on logical guesswork but I'll have genuine data, which appeals to the inner scientist part of my mind.

I'm also going to visit a non-Porsche repair shop near me to see if I can find anyone who can run a smoke test on the intake system to find vacuum leaks. I'll do that first and fix anything before the sensor replacement.

[kbrandsma]

With 104 K on the speedmeter, replacing the MAF seems resonable to me. Not sure if you are the original owner or have all the old service records from previois owner but if the the MAF has never been replaced I would replace it. (Autohaus less than $200) shipped.) Easy DIY. What will your Indy charge? Anyone in your area that can exchange yours with theirs to determine? Just a thought.

Edited March 25, 2011 by kbrandsma

[Dale_K]

I should have mentioned that I have another problem that could be interrelated. I get a loud "wooooo" sound from the vicinity of the fuel filler occasionally under light throttle. The noise is definitely vacuum related because it goes away instantly if I move the gas pedal in either direction. It's possible that this might be the source of a vacuum leak sufficient to confuse the engine computer. I see from other threads this could be caused by the charcoal canister control valves. The Durametric system can activate the evaporative control system (I think) so I'm going to begin with that subsystem first. I can look at the fuel trim levels and see if they change after I fix the evap system. It's kind of hard with an old used car because you don't know the prior history and so many old interrelated components are involved.

[BoxsterTaff]

Dale - i replaced my fuel cap as a preventative measure with a new one when I had the fuel pump changed out (just like other seals, the rubber degrades with age). I think it was 12 bucks or something like that from Pelican Parts.

[Dale_K]

Yeah, I have a new cap on the way from Pelican right now. I found a foreign car shop in Hot Springs, AR that has a smoke system for finding intake leaks and I have an appointment for Thursday to have it checked. This will probably turn out to be the most expensive MAF sensor in history if they don't find a leak, lol. By the time I pay for the Durametric, the smoke test, the gas cap, the vent valve, the oil fill tube (already done), I'll be into this project for $1,000 and I still haven't bought the MAF sensor that everybody says I need.

[BoxsterTaff]

Well good luck, my 1126, 1128 and 1130 codes were solved by replacing the oil tube, MAF and a good clean! Last night i went for a 90min drive North of Dallas, and all the hard work was worth it! :jump:

[hucqym]

Well good luck, my 1126, 1128 and 1130 codes were solved by replacing the oil tube, MAF and a good clean! Last night i went for a 90min drive North of Dallas, and all the hard work was worth it! :jump:

I sure hope your problem is fixed but just a word of caution. When my AOS was gone and I got these codes, I cleaned MAF and cleared codes and it all ran fine for a while. CEL hadnt come up yet but I checked with my durametric kit and the codes had come back.

[Dale_K]

Yeah, I got over 350 miles before my CEL came back on after the oil fill tube was replaced. My generic code scanner won't display "pending" codes and the CEL sometimes doesn't get turned on by the computer until it sees the parameters wrong several drive cycles in a row. My local Porsche shop says they've never seen a MAF sensor successfully cleaned and totally clearing up the problem.

[wvicary]

Yeah, I got over 350 miles before my CEL came back on after the oil fill tube was replaced. My generic code scanner won't display "pending" codes and the CEL sometimes doesn't get turned on by the computer until it sees the parameters wrong several drive cycles in a row. My local Porsche shop says they've never seen a MAF sensor successfully cleaned and totally clearing up the problem.

I agree with your garage. I have cleaned many MAF sensors and it was temporary at best so I recommend just replacing the unit.

[hucqym]

Yeah, I got over 350 miles before my CEL came back on after the oil fill tube was replaced. My generic code scanner won't display "pending" codes and the CEL sometimes doesn't get turned on by the computer until it sees the parameters wrong several drive cycles in a row. My local Porsche shop says they've never seen a MAF sensor successfully cleaned and totally clearing up the problem.

I agree with your garage. I have cleaned many MAF sensors and it was temporary at best so I recommend just replacing the unit.

or the MAF may not be a problem at all (as in my case) so cleaning or replacing wont fix the problem.

If you have a durametric kit try reading actual MAF sensor values.

The OBD manual for DME7.2 specifes the following as expected readings

Switch ignition on: 0.9 to 1.1V

Start engine: approx 1.4V

[BoxsterTaff]

Yeah, I got over 350 miles before my CEL came back on after the oil fill tube was replaced. My generic code scanner won't display "pending" codes and the CEL sometimes doesn't get turned on by the computer until it sees the parameters wrong several drive cycles in a row. My local Porsche shop says they've never seen a MAF sensor successfully cleaned and totally clearing up the problem.

Sorry for the confusion - I installed a new MAF, the good clean was refering to the TB and intake system after the AOS was letting out........ So far the only CEL code i have thrown is a P0430 which is either a bad O2 or a bad Cat.....i'll get to that later!

[Dale_K]

OK, some progress today at the local foreign car shop in Hot Springs, AR. They hooked up their smoke testing machine for locating vacuum leaks and found a pretty big one on a line that exits the driver side intake manifold right behind the driver's back. The line turns left and runs about 6" then goes down to the bottom of the car and I think it goes forward at that point. The reason I don't know for sure is that I was in the car raised in the air wiggling the line while the 2 mechanics were underneath making sure they knew which one it was.

Looking at the shop manual and parts diagrams it must be the vacuum line to the brake booster. Possibly part # 996 355 577 42 for a 2000 S but I can't find a diagram in the parts catalog that specifically shows the hose from end-to-end. It would have to be a pretty long convoluted hose if it's one piece.

The main point of this post is how valuable the smoke testing tool is. I doubt a home mechanic would have found this leak and I know for sure that one Porsche shop didn't find it when they searched for leaks and didn't use a smoke machine. The line was rubbing against the chassis as it turned down from the top of the motor. The mechanic said he saw a small wisp of smoke and then when he wiggled the line it blew out smoke like crazy.

And although the full story isn't over until I get the line replaced and spend enough time with the car to know it's fixed for good, this also points out that jumping to a conclusion that it must be a bad MAF sensor might be expensive and frustrating. Not saying it still couldn't be a sensor but I'm glad I searched for the fundamental stuff first.