heyy, no worries. Would hate you to rely on a battery disconnect, though.

 

OK, took the car to the dealer on Monday. Explained car runs great, check engine goes on or off sometimes for several days, sometimes on one day off for a week. They "smoke" checked for vacuum leaks and said there were none. They cleaned the injectors and changed the fuel filter, road tested and cleared the codes (P0171 & P0174). When I started the car to leave the dealer the light was on. It was off when I took it in. Had to leave it.
Then they replaced the MAFS and called me today to pick it up saying everything was OK now. Started the car to leave the dealer and the light was on again.
Does anybody have any ideas?

 

Hi fogeyo, don't worry, jagv8 isn't annoyed with you. Look at it him this way: He's an intense passionate diagnostician who's usually a step or two ahead, otherwise a very giving person. He's helped many here sort through issues in a logical manner. At this juncture he firmly believes the least painful measure in regards to time and money is for a certified Jag tech to take the riegns. However, it seems even that step has born little fruit. Has anyone analyzed the four O2 sensors for faults? I recently had the check engine light go on and off a few times. The code was for a faulty O2 sensor. Before I could replace it the light went out.

 

Sorry, I came in on this thread on its later posts and now after reading earlier entries realize there had been suggestions of faulty O2 sensors.

 

I am not sure what you have going on but my best guess is that it is a vacuum leak and engine operating temperature has a lot to do with the timing of your codes appearing. I am going to send you a few links that might help http://www.gusglikas.com/images/Auto...od%20Latch.pdf My car is not like yours (3.0) but wanted you to know what I had and how I found it. I used 2 cans of the TB cleaner to find and a lot of guidance and patience. This is a procedure that might help you get started in identifying your problem http://www.gusglikas.com/AutoRepairTroubleShooting.htm This is not an answer to your problem but it might help you find it. Please let us know what you find, we want to help.

 

Thanks all. Gus something I saw on your reply......If the problem was corrected and they road tested for a short time and parked it after clearing the codes until I picked it up your comment was this has to be learned and it won't just go to 0 directly. Does this mean it has to go through several driving cycles until the values return to a normal level meaning the light can still come on and the codes still show up for "X" period of time? Hope this is clear enough!

 

Not sure that is what I said; however, it is possible but highly unlikely. On the most part after a repair and the codes are cleared you will not see that code until it is broken again. I could agree with the theory that you had two problems and only one was found and fixed. Do you know what they found/repaired the first time?

 

First time they cleaned the fuel injectors and changed the fuel filter. Second time they changed the MAFS. The light came back on after each.

 

Have you given the car enough time to learn your conditions? IE how you drive, the fuel in your area, your air density, altitude?

I left mine alone and after 100 miles it sorted itself out. I can bet you money if a hard reset is done and codes cleared to P1000 aka not ready my P0171 and P0174 lean banks will return until it learns conditions.

You haven't mentioned the obvious what octane are you using? Clear the codes if you can with less then a 1/4 tank drop a bottle of 104+ octane booster fill up with a relaible fuel IE chevron or BP sunoco 91 or greater to induce a rich condition and monitor the pending codes.

You can manipulate our ecu's via the fuel. Trust me I know for the dyno run I was able to achieve a solid lambda aka 14.5 afr I data logged one of the pulls it didn't pull timing and ran like a scalded ape. Sure my whp is kinda low at 318. But it was less then ideal conditions with 120 degree AIT temps. But somehow pulled 341 foot lbs of torque which is pretty on par for stock.

Anyways back on track what's up with your fuel?

 

The place to read about codes (like how long for one to flag up) is the workshop manual (ebay about $10).

The ideas about them and OBD are all over the net but there's plenty to grasp - not a small subject.

Dyno & WOT - car runs OL (open loop) which is not how it runs most of the time. In CL (closed loop) it uses the O2 (and other) sensors, which better be working.

After a battery disconnect you should not get lean (or rich) codes. But with a modded car, I guess many values are not what the PCM expects so MAYBE that's why. You'd want to watch fuel trims at idle and again at about 2500-3000rpm.

Cleaning injectors can't hurt, apart from smallish cost. Changing fuel filter, MAF, whatever.... can mean no-one watched the OBD values to see what's happening. The fuel filter's cheap but the MAF's expensive!!

 

I agree with Jagv8, you should get an Elm27 obd2 tool datalog the car and perhaps post it up maybe we can help out a little better. Fuel trims, timing advance, reading the vacuum sensor can help figure out what's going on.

 

The car is still at the dealer. It has been a full week now. After the first two 'repairs" that did nothing they are saying they smoke tested again and found a leak in the pipe from the EGR to the intake manifold and they are replacing it now. Does that sound like it could be the cause? Does anyone know ballpark what that would cost? They couldn't geive me an answer yet. Since they took the time to take the new MAFS off and put the original back on I am concerned when they total the bill they will include that charge which should not be done.Thanks

 

hmm, I might have the same leak. I might have to take it in to the dealer.