1998 Idle/check Engine

[andypalmer]

I have a 1998 Explorer 4.0 SOHC with 71k. Since the onset of winter it has started idling oddly. It will idle around 700rpm, as it should, but will occasionally dip to around 500-600 and feel like its about to stall. Also at normal idle there is sometimes a shudder which becomes more noticable when put into drive. I also have the check engine light.

The codes read out were:

P1131 Heated O2 sensor 11 sensor indicates lean

P1151 Heated O2 sensor 21 sensor indicates lean

P0171 System too lean (bank 1)

P0172 System too rich (bank 1)

P0175 System too rich (bank 2)

It has been suggested it may be both O2 sensors, sticking stepper motors or possibly contamination in the manifold.

Anyone cured this before? Any suggestions as I have just had a major service, engine flush, brake pads, fan and auxiliary drive belt tensioner done and would prefer not to throw any more money down the drain?

 

[dynamite196]

looks like an intake gasket leak

 

[Howard]

Those are the classic symptoms of a lower intake gasket lead. Do a search on OOM12. Its a fairly straight forward job just take your time and don't drop anything down the inlet ports.
http://www.explorerforum.com/forums/showpost.php?p=487634&postcount=33

 

[andypalmer]

How would I confirm this and/or rule out other possibilities? I don't really want to throw money and parts at the problem without a fair degree of confidence.

 

[Howard]

Well I look at this logically. It is very unlikely for both O2 sensors to fail at the same time. The system cannot be weak and rich at the same time. The parts for the kit are very cheap and if you do it yourself the job is a no brainier. I've had the self same problem with those very codes. OOM12 fixed mine a treat. I believe the test is to spray butane gas around the lower manifold and if the idle evens out then there is your leak. Not very keen on spraying inflammable products near an engine. Also does the idle improve with a hot engine. It is also worth doing just to improve the timing chain tensioner with the revised version found in the kit. So you may kill two birds with one stone.

 

[andypalmer]

The idle does not really improve with a hot engine, still drops a little and still has the occasional shudder through the brake pedal.

 

[andypalmer]

Also the code for one bank being too rich is throwing me. I had the codes cleared a day before these appeared to eliminate any old codes. The previous codes were the same for both O2 sensors and BOTH banks lean and rich. Would this suggest a different fault or just overcompensation from the lean condition? I am also considering a sticking IAC.

 

[Howard]

I think the rich code is simply the system pumping fuel in to compensate for the lean condition. Cleaning the IAC cannot hurt and may help.

 

[andypalmer]

Is the revised tensionner for the front or back ie does the engine need to be removed? Pain if it does.

 

[Howard]

Neither tensioner needs the engine removed but the revised one in the kit is for the front as per the install instructions in this post http://www.explorerforum.com/forums/showpost.php?p=487634&postcount=33 . The front one is normally the one that goes and only requires that the inlet manifold be removed hence the new 'O' rings in the kit.

 

[andypalmer]

What would you suggest would confirm categorically that it is the manifold as I don't want to waste too much money if it is not the problem? Would the O-rings be visibly shrunk/worn? Would there be an audible vaccuum leak from this area? I am not confident in doing it myself so would obviously need to pay labour charges, probably around 4 hours?

 

[floydr007]

I need to get my lower intake manifold o-rings replaced, as well. I was curious if any of you had a shop do the whole 00M12 for you, and if so, how much did it cost? I just want to know a reasonable time estimate for a shop for this job (both the o-rings and the tensioner), and how much is the actual kit from Ford? Thanks a lot.

 

[steve6534]

What would you suggest would confirm categorically that it is the manifold as I don't want to waste too much money if it is not the problem? Would the O-rings be visibly shrunk/worn? Would there be an audible vaccuum leak from this area? I am not confident in doing it myself so would obviously need to pay labour charges, probably around 4 hours?

I would try the "propane enrichment" test. When the engine is cold start it up and move an unlit propane torch near the intake manifold areas. If there is a noticeable vacuum leak the idle speed should change as the propane is drawn in the manifold and burned in the cylinders.

 

[andypalmer]

Well, it seems it is the inlet manifold. Just deciding wether to get it done or sell the truck. As UK Ford dealers are useless with Explorers does anyone know the part number for the kit and the recommended extra washer if I do decide to go ahead with it?

 

[b0_n_jen]

P1131 Error Code

1997 Explorer 4.0 SOHC

About 1 month ago my check engine light came on. I had the codes read, and came up with P0174 & P0171. I did some research on this excellent sight and concluded that it was the upper and lower manifold gaskets. I got the kit from my local Ford dealer and replaced both the upper and lower gaskets. And they needed it by the looks of the old ones.
Problem solved, no more check engine light, untill today. Check Engine light is back on. Had code checked and now am getting a P1311, bad 02 sensor.
At $51 dollars each I don't want to change both of them. Is there a way to tell which one it is?
Any help or comments appreciated.

Thanks