Discovery I Issue

[hoberock]

I have a 1997 Disco I with the 4.0L engine. It has an idling issue. Some days it idles too high and others it idles too low. If is idles OK on a cold start (rarely will it idle too low on cold start), sometimes it will idle too low if I restart it warm. If it idles too high on cold start (idles too high, but once I am stopped, it will idle down), I can turn off the ignition briefly, restart, and it will go away. I also get a P1179 code on occasion (AMFR Correction At Maximum Negative Value). Here's what I have done so far:

- Replaced Fuel pump
- Check Fuel pressure on Fuel Rail (~35 psi)
- Cleaned MAF sensor
- Cleaned Throttle Body
- Cleaned IACV (Idle Air Control Valve)
- Cleaned Valve Cover tube into Throttle body
- Electrically Checked the TPS (Throttle Position Sensor)
- Checked both O2 senors 1 (both Banks) for switching
- Checked both O2 senors 2 (boht banks) = Not sure of the behavior for these
- Checked fuel pump electrical circuit
- Cleaned Throttle assembly and checked for binding
- Cleaned all electrical connectors (TPS, IACV, MAF, etc..)

A P1179 fault indicates that the system is getting too much air and the ECM can not add enough fuel (with in limits) to compensate. I am not sure if that is related to my idling high and low issue. The Rover has about 130K miles on it and I am not sure if any of the O2 sensors have been replaced in the past (bought the Rover a few years ago used). However, I am pretty sure this is not a problem with my O2 sensors. I checked the vacuum system for leaks and did not see any. The IACV seems to be opening and closing but I am not sure if it is opening to the proper number of steps. Any help here would be greatly appreciated. I have posted on other boards, but have just gotten the "regular responses" (replace your O2 sensors, clean everything in sight, check you fuel pump, etc..). Nothing too useful or that has come close to helping. Hopefully, someone on this board can help me out. Thanks!!

[RoverChic]

There is a very good possibility that you need to have the ECU re-mapped, depending on how long the system was running with the deteriorating fuel pump. Hence the random idle problems.

I had P1179 as well on the D1, I changed out the MAFS as well as the Air Filter and cleared the codes. This resolved the P1179.

I did however have to have the fuel pump replaced. Because I let the fuel pump and the fuel system die out rather than address the issue immediately, the rover became accustomed to running on a less than ideal fuel system. Therefore when I replaced the pump, the ECU was "confused" thereby needing to be re-mapped. This can only be done at the dealer or by any shop that owns a RoverCom. The idle was VERY high in all gears, around 2500 RPM's. It was suppose to re-map itself however that never came to fruition.

HTH!

[beavis4g63t]

Do you have a leak after the maf?

[hoberock]

Thanks RoverChic for the input. I disonnected the battery for a while to try to clear any resident learnings in the ECM, but that did not help. Also, the problem did not start up immediately after the fuel pump was repalced (~2 months after the pump was replaced.

beavis4g63t, no leaks after the MAF that I could find. I used starter fluid and sprayed around the MAF, hoses, and intake assembly looking for a idle up if there was leak. No leak was found. I also visually inspected all hoses. To test the leak theory, I created a leak by removing the hose clamp on the exit side of the MAF and let air into the intake (after the MAF). This caused the engine to idle down, however, I had to create a big leak to get this behavior. This also does not explain the high idling issue.

Any more ideas?? I currently suspect the MAF and/or the ECM. I am trying to get a hold of an extra ECM and MAF to swap them out to see if this helps (anyone have an extra one or both of these so I can try this??).

Thanks

[beavis4g63t]

Check the wiring wherever you can. Someone local to you should have some parts for you to swap. Try dweb because they get more traffic.

[RoverChic]

Originally Posted by beavis4g63t

Check the wiring wherever you can. Someone local to you should have some parts for you to swap. Try dweb because they get more traffic.

Yes search through the archives on DWEB. There is an actual thread that says P1179, I believe it was started by Jamie. Has lots of good information!

[fivespddisco]

mel is that you?

[Disco]

Check all pipes and hoses, from the Air Flow Meter to the Plenum chamber, for leaks or splits. If there's no problem there, you may need to investigate your electrical system.

[rovermech]

Doing everything youve done, You might and try to find somebody with Autologic computer or WDS at a dealership and have the adaptions reset. I had do do this on a 98 a while back hat sounds like it was doing the same thing.

[RoverChic]

Originally Posted by rovermech

Doing everything youve done, You might and try to find somebody with Autologic computer or WDS at a dealership and have the adaptions reset. I had do do this on a 98 a while back hat sounds like it was doing the same thing.

Thank you! I forgot what it was called now (Reset adaptations). But I had to have the same thing done on my 1998 after the fuel pump...Get it hooked up to RovaCom to see what is going on! Let us know what you find out!


Hi Justin! Yes, it's Mel!

[300bhp/ton]

Every idle issue I've come across on any vehicle has always been a sensor type problem. I'd try swapping the mass air flow, and as you already said trying another ECU might be worth while. Is there not any chance of getting one from a breakers to try on a sale or return basis? I've done it loads of times here in the UK for various vehciles.

[afirover]

is their any chance that you have an injector stuck open ?????

[RoverJoe]

Bump!

Hey Hobrock.. let me know if you work this out.. I too am having the exact same situation, too a tee!

Best of luck.

[afirover]

same thing happend to ovis 1

did some stuff over the years
replaced throttle cable
installed a BIG spring on the throtle mech
but found the plunium was rubbing on the flapper and alowing the truck to act nuts

if you put it in drive once you get it started doesit do ok untill you shift back into park when the revs go up up up this is what we had

removed the plunium and filled it down allso look for side to side movment on the "flapper"

hope this helps

[Elemental]

I didnt see it mentioned. Did you check your PCV hoses on the valve covers going to the plenium?