Bank 1 lean, Bank 2 lean.

[PPro]

Autozone guy who pulled the code said leaky vaccum hose. Friendly mechanic said MAF...

Any other input? I understand it could be a number of things, what all should I check/replace? Please explain well, I'm still learning where everything is under the hood.

Thanks

 

[Eneurb]

If it's a 4.0 SOHC, the upper plenum seals are likely leaking. Also check for a dirty MAF sensor. Don't start replacing things as you can likely run up a bill for your guesses that would cost you more than a diagnosis at a garage.

 

[PPro]

I plan to clean the MAF soon. Is there a way to fix leaky plenum seals?

The guy at autozone reset the CEL and it hasnt come on since, does that mean that it no longer detects the problem, or that resetting it 'ignores' it? If it just ignored the problem I wont have a way of knowing what was the actual cause of the code...

Oh, yes it is the 4.0 SOHC.

 

[BuffaloXplorer]

No, it won't ignore it, and eventually it'll come back. I'd agree that you've got a vacuum issue. As far as fixin the plenum seal, i'm not sure...

To clean the MAF, just open up the airbox and spray the filaments with electric parts cleaner (liquid, not canned air). Some say to use a q-tip but i'd be afraid of breaking the filaments...

 

[Eneurb]

You can remove the 2 tamper-proof T20 screws that the sensor to the housing. I like to use a fine paint brush to clean them, you don't normally need to use any type of chemical. If you are to use a chemical, do not use anything chloronated like brake clean, as it can crack the ceramic coating. If the intake seals are leaking, they would need to be replaced.

 

[TPLYNCH]

PPro - search for 00M12 and 01M01. The intake manifold o-rings on the SOHC engines were defective and leaked. Most common symptom is rough idle at cold startup.

 

[PPro]

Thanks TPLYNCH- I just cleaned the IAC hoping it would cure my rough idle (which it didnt.)

Hopefully that will help.

 

[BMWU]

00m12

I had the exact same problem codes. Thanks to the info on this board I ended up at my Ford Dealer and they performed the 00M12 owner notification repairs. It was only done yesterday, but everything seems to be great.

The mechanic said it is still reading a little thin, which may be caused by a dirty MAF sensor. I was shocked when the did not recommend replacing, a stealership telling a client to wait and see on something they can make money on? This may be a first.


I will probably try cleaning the MAF myself.

 

[expospt98]

Is it hard to replace the seals? I got a 98 4.0 sohc w/ the same problem. Is it something i can do myself?

 

[rdecker83]

Well I don’t know if I’m right but I believe Bank 1 refers to the side cylinder No.1 is on the engine and Bank 2 referrers to the side cylinder No. 2 is on of the engine and if you are getting a Lean condition your O2 (oxygen)sensor is detecting a lean condition so first would check for vacuum leaks, then I would replace both of the O2 sensors, now you didn’t specify if the were the sensors before or after the catalytic converter. Sense the EFI system is detecting a lean condition you are getting air flowing into the engine past the MAF sensor (False Air), on thing I would check for is a stuck open PCV valve, I have see them trip computer codes before. Also check around the throttle body for vacuum lines, I believe the Purge Hose for the EVAP system flows in there so you could have a faulty EVAP solond (stuck open). But i have never seen a faulty intake manfold gasket before. I hope this information helps you.

 

[Eneurb]

Bank 1 is cylinder 1-3 (passenger side), bank 2 is 4-6 (drivers side).