Your Thoughts Welcome ..... Engine Revs Playing-up

[bob12]

Shortly after the 1990 745 (B200F LH2.4 with cold start injector) got its MOT a month ago it has started to play-up!!

Basically it starts OK but, then shortly after the engine idle revs (800/900) fall off and the engine will stall if the accelerator pedal is not used to keep the revs up. It's not easy to do stationary or coming to a stop as the revs seems to race away uncontrollably. All a bit of a pain!! Once driving the car responds just fine.

The code showing is 2-3-1. i.e. Self adjusting Lambda-sond not operating. Faults C1 (air leaks intake system with itemised checks to be done) and/or D1-6 (all associated with the fuel pump/pressure regulator and fuel lines).

I suspect that non-regular use is part of the cause as the V70 is now the car of choice! The fuel pump is OK.

At just under 150K from new I have never given much thought to the injection etc systems. I have to be frank the area of the throtttle body (TB) was looking rather rough/gummed up even from the outside at the intake pipe from the MAF at the TB. My principle has always been if it ain't broke don't fix it!! The plugs and leads/dissy/ rotor/ etc are all looking in need of some tlc as well having been in for some considerable years .... maybe the rotor and dissy 20!!

I am in the process of stripping out the lot and cleaning everything up having removed the TB today (not a pretty sight!). As the TB is off I shall then move on to the PCV system and all pipe work before turning my attention to refurbishing the other side of the ignition system on the engine.

However, today on removing the TB I was surprised to find a small puddle of petrol in the lowest point of the inlet manifold casting just inside where the TB is bolted. Ooooh, that's not good I thought! The car was last driven a couple of miles about 24 hours before.

Although I haven't considered the matter further or tested the fuel pressure regulator on the end of the fuel rail it looks like the rubber air pipe goes into the manifold near the TB intake. I am wondering if the fuel pressure regulator has finally given up/perforated and is the source of the petrol?

I have not yet considered the Idle Air Valve but that will be released to get to the plastic crankcase ventilation oil separator. I seem to recall there are tests that can be done out of the car to check it is opening and closing.

I would welcome any thoughts that might help me sort this 'little' niggle out.

Cheers, Bob