Running too rich & cuts out at idle

[minirace]

I have a 94 430, a great car but recently started running rough and cuts out when I slow down to idle. It appears to be running very rich, I have cleaned stepper and butterfly. Done all sensor & ECU checks as per Steve Heath Bible, all as should be except airflow meter reading 3000 rpm at 1500. Could this be the fault or do you have any ideas.

Thanks

[jigs]

Check your fuel injection relays are operating. Then try resetting the ECU.

[minirace]

Jigs, thanks for the reply, what and where are the fuel injection relays.

[jigs]

They are the two Bosch metal 5 pin relays in the loose loom that sits on top of your battery in the passenger footwell.

[Big Al.]

jigs said:

They are the two Bosch metal 5 pin relays in the loose loom that sits on top of your battery in the passenger footwell.

jigs, aren't they the one with the red cross on them?

[shpub]

If the fuel injection relays are not working there is no fuel pump and no fuel pressure. That means the car will not start or run very lean. Usually that means not starting at all. That is the opposite of the damp/wet spark plugs that were reported and the funny misfire.

[jigs]

Big Al - yes they have a red X on them and cost about £18 each - Land Rover part.

Shpub - sorry to disagree but - last year I had a problem with one of the Bosch 5-pin relays which meant that power was not going to the Air Flow Meter therefore making the engine run very rich at all times. Caused similar problems to those described - could be something totally different of course.

Worth checking out - swop the two relays over and see if that makes any difference.

>> Edited by jigs on Tuesday 14th October 10:44

[shpub]

Fair point but no power to the AFM would cause the ECU to record a fault code 12 and I would also expect to see other more catastrophic failures as they supply power to the other parts of the fuel injection system. e.g. injector banks and ECU. No power to the injectors is pretty terminal.

[jigs]

No - only power cut to AFM - injectors , etc all functioned - had me puzzled for a while.

If you check the fuel injection wiring diagram you'll see that this is possible.

Lesson - expect the unexpected.

>> Edited by jigs on Tuesday 14th October 11:06

[shpub]

Just checked them and the only way the AFM could be powered off on its own through a faulty relay is if the internal link inside the relay was broken so that the power out to the AFM was O/C while the second power out to the injectors was OK.

As the two power out connections are usually the same bit of folded metal, it was a pretty strange fault as these usually fail completely O/C with no power. Either the internal electronics dies or the contacts die and make both output pins O/C.

No wonder you were stumped. As you say expect the unexpected.

[jigs]

Yeah - only TVRs and women can be so perverse - don't you just love them - both.

[minirace]

THanks for your argument, suprisingly the relay that you are talking above seems to have got wet in the foot well as it has rusted, I replaced it with an old one which Mole Valley replaced a few years ago, so maybe that one is faulty too. I will order a replacement and let you know. THanks again.

>> Edited by minirace on Wednesday 15th October 20:21