I have a 1997 Disco I with an idling issue (4.0L Gas engine). This is a weirdissue to me. I'm pulling a P1179 fault code on occasion (I can clear it and it will go away for a while). The book says that the P1179 code is AMFR (Air Mass Flow Rate) Correction at Maximum Negative Value (also have seen is as: O2 sensor signal circuit slow switching from rich to lean, Bank 2 Sensor 1). I have monitored the two O2 sensors and I am getting signal from both (and they seem to be switching between Lean and Rich as they should.....). At cold start it idles fine most of the time. For warm start, it won't idle most of the time, but if I give it gas itseems torun fine. This issueis getting worse over time (meaning ishappening more often).When itfirst started happening, I could turn theignition off and wait a few minutes, then start the LR up again and it would run fine. Now it does not goaway until the engine cools down. Every once and a while it will idle too high (idles high then will drop down after sitting for~ 30 seconds).This problem also goes away if I turn off the ignition and wait few minutes then restart as well. I'm not sure if the two problems are related. Here's what I have done so far:

1) Replaced the fuel pump (needed to be replaced anyway)
2) Checked the full fuel electrical circuit (relays, cut off valve, etc..)
3) Cleaned the MAF (Mass Air Flow) sensor and connector
4) Cleaned the Stepper valve assembly and connector
5) Checked the TPS (Throttle Position Sensor) and cleaned it
6) Checked all vacuum lines
7) Cleaned Throttle body and linkages (also checked for looseness or binding)
8) Checked fuel rail pressure
9) Replaced the fuel filter
10) Replaced the air filter (using a K&N filter now)

I found some information on the web about this issue and the following causes have been listed for a P1179 code: Bad O2 sensor(s), bad MAF, leaking exhaust, vacuum leak, fuel pressure issues, bad valve, bad injector(s), and bad coil.

Sense this seems more of a warm start issue, I am not sure any of these apply.... the book also says that it could be the stepper. I also thought this might be aproblem with my ECU. Any ideas? I could really use some help here. My LR is almost not drivable due to this issue.

Thanks,
Tim

 

I was just read the service book and I did not realize that there are FOUR O2 senosrs (two before the CAT and two after). My OBD II program shows Bank 1 Sensor 1 and Bank 2 Sensor 1 Switching between lean and rich (1 to 0). However, Bank 1 Sensor 2 is between .1 and .2 and Bank 2 Sensor 2 is between 1 - .3. I am curious if anyone knows where each sensor corresponds to for the Banks and Sensor numbers.... It may be that I have a bad O2....

Thanks,
Tim