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westonben

3.9 Bad Idle

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Ben

:blink:

Before you do anything else, try this:

Grub around in your drivers foot well (drop the pannel under the steering wheel down) and find the diagnostic socket which the dealer uses to pug the fault code reader into. It is is often taped or cable tied onto the loom. If you can't find it let me know and I will photograph mine and post it.

It will have three wires going into it and a blanking plug inserted into the socket.

The blanking plug will in turn have a single wire coming out of it which is taken back to the wiring side of the socket. If this plug/socket and jumper lead arrangement is not properly connected (in effect cross connecting two of the three wires properly), your engine will exhibit all the symptoms you are describing and run like a bag of the proverbial at idle. This is because the ECU thinks it has a fault code reader attached - and doesn't - which screws up the high / low logic inputs to two of the pins into the ECU.

You may find that some plonker in the garage hasn't replaced this blanking plug properly last time they pluged in the fault code reader!

Then strip down the plug and socket and clean up any surface corrosion on the surface of the pins with a fine emery paper. Crimp the female connectors slightly to ensure a good connection. Reassemble and reconnect. Disconnect the battery for 30 seconds. Reconnect battery and restart.

Very simple but not a lot of people know about this one. I would do all this anyway however because it may be that you have this fault intermittently which is compounding something else and making that difficult to diagnose.

Alistair

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Grub around in your drivers foot well (drop the pannel under the steering wheel down) and find the diagnostic socket which the dealer uses to pug the fault code reader into. It is is often taped or cable tied onto the loom. If you can't find it let me know and I will photograph mine and post it.

Alistair,

Thanks, will take a look at this. Can you identify which is the socket you are referring to from my picture? Is it the orange one?

Thanks

Ben

DSCF4031.JPG

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This is why I always go for a diesel motor.

Less things to go wrong and thus infinately more reliable.

Ah but when things go wrong on a petrol engine they can usually be home serviced and don't often cost £450 (diesel injection pump) or £250 (turbo) ;)

After a brief foray into diesel ownership I am now going back to petrol because there is less on a petrol engine that I can't diagnose/fix - even within my very limited budget... (and I also happen to have one on the drive so it's effectively free)

Back on-topic - the orange thing taped to the loom is the tune resistor, but I am afraid that I can't help with the fault-code reader connector. There is reference to 17EM FAULT CODE DISPLAY UNIT - RR2814h-l in the manual, with the following information:

1990 model year vehicles have a fault code display unit which is located underneath the right hand front seat, adjacent to the EFI ECU. The unit will display the relevant fault code, in addition to the EFI warning light being illuminated.

But mine doesn't have the display unit so I don't know where it would be plugged in. I'll have a look around the wires when it gets light.

Roger

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Very simple but not a lot of people know about this one.

Although it does form part of a LR Service Bulletin for this carp idling problem. :rolleyes:

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I did have the Air Mass tuned just last week (by Bosch) but I guess the ECU is adaptive and I never drove it long enough with the new sensor on before getting it tuned?? Either that or they just didn't know the correct target setttings??

With no O2 sensors it'd be a good trick if your ECU could self-tune to any useful degree with no feedback :huh: and since I've got my pessimist hat on, I doubt the diagnostics plug is going to yield any information you couldn't find by doing some simple tests yourself. The problem with diagnostics is the system has to know it's faulty, more often than not diagnostics leads you the wrong way by reporting unrelated symptoms to the actual fault.

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Ben.

The diagnostic plug is white. That orange one is the tune resistor...but I have to agree with Fridge though.

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