First let me say I like dealing with AB, there stuff is alway on my door step in 24 hours. But before you go with the 02 sensors from AB, there was a post last week or so from someone who went thru 3 sets of those 02 sensors.
They end up returning them and going with NOS ones from British Parts of Utah in order to there truck right.
Amazon is also a good place you can find NOS ones from $60-$80 ea. if you do a search on 02 sensors you will probably find postings simular to the one from last week.

 

OK, new MAF unit is in and truck seems to start a bit easier. No longer get the P0171 / P0174, but still have the P0150, but says pending...

Anyway, I still want to clear off the passenger side O2 connector, as it is covered with oil. I want to then tighten down the valve covers, as they are leaking oil like a sieve....

Almost there...

 

This is really getting crazy. Put in two new front (precat) O2 sensors from AB, and now getting P0134 - no O2 circuit.

Also, the truck is misfiring like crazy,,,all sorts of cylinder misfires.

When I unconnect the MAF sensor, it runs good with no cylinder misfires...I get codes like no intake temp and no MAF input, and still the P0134 no O2 circuit...also seems to start right up when warm (haven't tried cold yet)

I will return the MAF sensor. The old MAF sensor is also no better....misfires everywhere.

Any ideas? How bad is operating the truck without a MAF Sensor? At least it runs well...

 

I have repurchased the supposedly correct O2 sensors from the British Parts of Utah ...I don't understand how AB can be selling O2 sensors that won't work on my model Disco 2.

I will also try another MAF from BP of Utah too...the new one I installed was off eBay from Chandler motorsport and supposedly was good to go...

 

Do you have a scanner that can display data? What are the MAF and o2's reporting cold, warm, when running "better" and while missfiring?

 

Yes, I have a laptop based scanner that will track that data. I can try to log that info tomorrow.

With my luck, it will not missfire if I track it....

 

Hello all,

Ok I ran my USB OBD II Scanner (scantool.net) and system was cleared of all previous codes.

I was in garage, with AC on (its hot out today) and idle:

Eng RPM - 739
Calc Load Value - 5.5% - 16% (varies with Throttle)
Timing Adv Cyl #1 - 11.5 degree - 13 degree (varies)
Airflow - 1.2#/min (varies with throttle)
Fuel System #1 - Closed Loop
Fuel System #2 - Closed Loop
Short Term Fuel Trim Bank 1 - -1.6% to +.8% (varies)
Long Term Fuel Trim Bank 1 - +14.8%
Short Term Fuel Trim Bank 2 - +.8% to 3%
Long Term Fuel Trim Bank 2 - +14.8%
Intake air - 140F
Coolant Temp - 199F
O2 sen 1 Bank 1 - .07V to .725V (varies)
O2 sen 2 Bank 1 - .75 (somewhat steady)
O2 sen 1 Bank 2 - .1V to .75V (varies)
O2 sen 2 Bank 2 - .4V to .75V (somewhat steady

I took an easy drive around the block and following codes appeared (but no misfires)
P0134
P0171
P0174

Next, I throttled it up to 4000 - 5000rpm and misfired like crazy, and got the following additional codes:
P0103 (MAF High Input)
P0301 (cylinder #1 Misfire)
P0303 (cylinder #3 Misfire)
P0305 (cylinder #5 Misfire)
P0307 (cylinder #7 Misfire)
P1300 (MAF something or other)
Pending P1510 (manufacturer specific)
Pending P1551 (manufacturer specific)

I think the P1510 / 1551 is IAC related. I sprayed some contact cleaner into the IAC connection yesterday and this could be loose...I will check...

 

OK, got the Bosch O2 sensors and MAF from BP of Utah. I also replaced the 1, 3, 5, and 7 spark plugs (the other four will be replaced shortly). The Truck runs great now, with zero misfires. Even when I jump on the throttle, it runs fine.

Although does throw a P0171 / P0174 "Pending". Does the computer need to 'learn" the new MAF and O2 sensors?

 

Changed the other side of plugs. Runs fine, but still has code P0171 / P0174. I can clear them all day and still will come back.

Don't seem to have any vacuum leaks anywhere either...

Read that gas with 10% ethanol can trigger the Lean codes...I am quite sure the BP I go to has ethanol, but I always get premium...

Also read of a required reset of the ECU after new O2 sensors and MAF??

 

OK...maybe some good news. I took off the IAC and it was caked with crud. But one thing I noticed is the plunger was locked in a position that left a gap for the air to pass (and bypass the throttle butterfly valve). Anyway, I spayed a full can of carb cleaner inside of it and it came loose - it bounced around like a bobblehead. I put everything back together and she started right up...this was a good sign to me as it usually took me two to three cranks to get her to turn over. Anyway, plugged in the OBD II and cleared the P0171 / P0174 faults.

I went to the sensors while idling, and read that the Short Term Fuel trim was mostly in negative for both banks, and the Long Term trim was 24.8 (used to be around 15). I think this means more gas, which is good. Also noticed that all four O2 sensors were reading a hell of a lot closer to .75V than before. A few .1V here and there when changing throttle patterns (shifting gears, or coming off a stop), but before cleaning the IAC, the O2 voltages were a lot more unstable. Again, good news here...I will reserve total victory until I go a few hundred miles with no SES lights...

But now that got me thinking, if the IAC was stuck letting air bypass the throttle body, you could get a lean condition, as the computer may use the Throttle position sensor to meter flow and not the MAF. If the IAC is mainly used on startup, when working properly, the mass flow rate from the MAF and Throttle position sensor should match, correct?

I feel like I am talking to myself here (no-one has posted a reply for a while), but maybe someone is reading this and can get some use and some direction...I will post back after a while...