marcodant

Ok the check eng light just showed up again.. I love trying to figure this out.. Learning lots

Ok
Paul or others.. I have a question. Now I get this code on my fault codes. Notice (add). on the bently it states ---The term "Add." = additive; applies only with engine running at idle speed. Does this mean that my car is running lean ONLY when at idle?? I get the same code for bank 1 also--17544 - Fuel Trim: Bank 1 (Add): System too Lean P1136
also what is the difference in

17544 - Fuel Trim: Bank 1 (Add): System too Lean
P1136 - 35-10 - - - Intermittent
and

17544 - Fuel Trim: Bank 1 (Add): System too Lean
P1136 - 35-00 - -

notice one has 35-10 at the end and the other 35-00... thanks guys

ttuling

Above idle, the problem may still exist but it doesn't cause the computer to adjust the mixture so much that it logs a fault. For example, a small vacuum leak that delivers a significant percentage of the air used by the engine at idle may not be significant at part throttle. (The fault codes happen when oxygen sensors report a fuel/air ratio that's too different from what the computer expected by reading the MAF and other sensors. The computer will adjust the fuel quantity to try to balance the mixture, and it may succeed, but if it has to adjust too far, that's a fault.)

The difference between the codes with 35-10 and 35-00 suffixes is that one is Intermittent.

Turns out I guessed wrong when I said a leaking EVAP valve would cause "too rich" codes only. Mine seems to have caused "too lean (mult.)" codes on both banks a few days ago, and 5V part of the Bentley says it can happen (for mult. codes only though -- strange). I guess the engine started breathing through the gas cap. There was also a large evap leak code a few days earlier. The valve's been changed for only a few days -- not declaring it fixed yet.

Tom

marcodant

what year do you have? did you get the same fault codes I did? Also the strange thing with mine it went away and now back...the car seems to idle ruff. all the measuring blocks are good according to bently. and both banks are faulting.. If you remember back I said I found a o2 sensor wires laying against the exhaust pipe. well that same o2 sensor seems to have a issues now.. sometimes the vag sees it and reads well other times no readings.. might have a open in the wiring. I will test it tonight...I am going to do the rectifer trick on it too..see link in tech section under Ga and o2 sensor modification.. I hope that also works. But I have a feeling I still have a vac leak someplace as well as that post cat o2 sensor that needs to be replace.According to the vag the evap tests good, the maf test good , the injectors check good, the o2 sensors test good, except the one that seems to have a issue every now and then. I followed all the steps in the bently and and hitting walls now. the only thing I have left to check is the fuel pump system. If you have any more Ideas please feel free to share. otherwise I will be playing again tonight looking for leaks and playing with that o2 sensor.

PaulW

If you don't find it tonight, just sit back and think about it for a few days, I bet you'll figure it out.

Nice detective work Sherlock! We would never know that you just got this car!

pw

ttuling

Mine's a 2001. It first gave a large EVAP leak code, not intermittent. Later it gave both banks mult. fuel trim too lean. Finally there was an evap flow incorrect. I never proved what was wrong, the problem would come and go -- it went from large leak to small leak to no leak by itself some time after I'd tightened the gas cap and had been working near the evap solenoid. Did various output and vacuum tests on the evap solenoid valve but it checked out at the time. Didn't replace it until the evap flow incorrect code. I hope that's what it really was, they're not cheap.

On your car, no new ideas beyond what you've stated. A vacuum leak wouldn't surprise me. It can't hurt to check fuel pressure, if you can get your hands on a gauge.

Are you meeting all the temperature etc. criteria for seeing the post cat oxygen sensor work? Maybe it's just cold or, if you're looking for an OK message, the test conditions haven't been met for self-testing on this driving cycle. Can you get it to say OK by generating a readiness code (not that I know this to work on your engine)? It seems odd that it doesn't cause a specific O2 sensor fault if it's dormant when it should be working. There are plenty of oxygen sensor fault codes, four or five to choose from for each sensor.

That rectifier thing -- nasty. You're on your own with that. No idea what new faults or emissions it might cause.

Tom

marcodant

yes I did get the car up to temp.. and yes all the measeruing blocks do get OK on them like they should according to benlty.. except the onc cat (sometimes) when that o2 sensor does not work.. But when it does I get a ok on that o2 sensor and then that cat test ok too. I get no evap errors or leaks showing up on the vag just those two codes and they usually show intermited. I will crawl around the car tonight and see if I can find anything else. this is a fun one.. buy the time I am doen figuring this one out I should open my own shop. LOL

marcodant

Ok update. That HO2 sensor (post cat) is shot for sure on bank 1. I did the fix suggested on the tech page and it works.. the o2 sensor now reads and so far no check engine light no faults. Still early but will keep a eye on it and keep you posted.. thanks for the help

Pearl 8

My 97 coded a lean condition both sides. Removed the center plastic cover found broken plastic Vac tee, replaced all tees, problem gone!!!! john

ttuling

I can't remember, did you swap that sensor with its counterpart on the other side?

It would be quite surprising if one bad oxygen sensor can cause lean faults on both banks. Let us know if this turns out to be the case.

Tom

marcodant

No I did not swap it (YET). But the rectifier did work on the one side. It will be interesting if it does effect both side. But the one thing I can confirm is that that fix did work for me on the bad sensor.. I will keep you posted. What a science experiment this is turning out.. I just hope when all is said and done that it will help someone else