The V8 Owners Forum -

Afternoon All,
I have just got my Landie back on the road, running a Thor version of our favourite engine. I.e. the one with a bunch of bananas for an intake manifold.

I have had the ECU sorted by Mark Adams to run in 'standalone' mode, and I have to say that even before I get it rolling roaded, it pulls pretty well. 0-60 is going to be about 7 seconds which I think is perfectly acceptable.

It is connected via a Helix 9.5" clutch to an R380 transmission, LT230 transfer and Range Rover axles. All standard stuff.

Now, it usually idles perfectly, but sometimes, when approaching a junction for example, it 'stumbles', but catches itself. Sometimes, it just conks out.

This should be impossible with fuel injection!!

I have tried a different idle speed control valve, and a different MAF, to no noticeable effect.

There are no adjustments I can make.

I am trying to get hold of Mark but haven't succeeded yet...

Anybody got any ideas on what might cause this? Or what I can test?

Thanks,

Chris.

From what you have said I would be looking further into the idle speed control valve. This is based on the engine is working Ok in other situations and only starts to play up in situations where the idle speed control valve comes into play.

Garry

I'd check the fuel pressure is correct, and the regulator working correctly. When on a trailing throttle, it will have set the pressure to the lowest due to the high vacuum. Has the engine still got cats and lambda sensors?

I am pretty sure the Idle Speed Control Valve is good. It's very free. On that design, it's rotary, so if you spin the body back and forth quickly, the valve moves nice and freely. I also changed it anyway.

I can measure fuel pressure, however this is the full fat Thor system so it has an in-tank pump / pressure regulator. There is no separate regulator or return pipe. The pump just gets 12V, and pumps, so it has no way of knowing engine demand. I am pretty sure it doesn't vary with engine load as I can't see a mechanism to do that!

It does have 2 lambda sensors and 2 cats. The cats are after the lambda sensors though, so they won't affect things.

I notice it is slightly rich I think as the tailpipe is black on the inside. I would have expected it to be clean still.

Chris.

I dunno the Thor (Bosch?) injection well, but would expect a single rail system to have the pressure controlled electronically?

As mentioned - in the Thor system the regulator is built into the fuel pump in the tank so the pressure remains constant and is not controlled electronically.

Not sure about a Thor system, but if I had this problem on a Hotwire system I would check the road speed sensor.

It's where a wideband sensor and readout would come in handy - to see what the mixture is doing when the problem occurs.