Calling Crasher-I'm desperate now!

[bobfrankish]

Hi Crasher, yes, I have tried unplugging various sensors when I first started having the fault, and the only one that stopped the engine was the G28. Anyhow there is a bit of an update...Today I decided to hook the scope up to the coil trigger wire (green/red) from the ECU to see whether the pulses altered in any way before the engine cuts out. I ran the engine at 2000 rpm for over half an hour, temp. gauge showed normal after about 8 minutes, no problems whatsoever. As soon as I let the engine drop back to idle, the engine began to idle roughly then judder and cut out as per usual. It refused to restart as usual, but the coil pulses are definitely there when the engine is being cranked. The fact is, I have been searching for this fault by letting the engine idle until everything gets nice and hot, then it cuts out. Maybe the fault is only at idle?

[Crasher]

Monitor the voltage to the fuel pump under the rear seat where it plugs in to the fuel delivery unit.

[bobfrankish]

Voltage on fuel pump stays constant around 13.4V with engine idling, drops to 0 when engine cuts out, and is around 10.5 with engine cranking but not starting. Hard to tell if it dropped immediately before engine cuts, but I don't think it did. Like you say Crasher, it would be good to run at about 2000 rpm so that there is some rundown when the engine cuts, but it does not seem to want to cut out if I wedge the throttle at 2000. All I can tell you is, just before it cuts it goes very lumpy and if you try to pick revs up again by blipping the throttle it jolts and cuts. It's also smelly, like rich mixture when you are cranking it and it is not firing. If you fully open throttle it will occasionally fire but won't run.

[bobfrankish]

Just as an aside, I have read an old thread which says that the throttle body settings are lost if the battery is disconnected, I regularly disconnect the battery for a couple of reasons, surely this cannot cause any major issues?

[mickeybo]

You posted up If you bridge out 2 relays you can eliminate trigger signals for both. Can you elaborate more on this please

[Crasher]

If you jump the 30 and 87 points of the relay you eliminate the relay itself and it’s trigger signal from the ECU. Not setting the TB adaptation can cause erratic stalling but not bad starting after; setting the TB in basic settings 098 is not difficult. Try running the engine with the lap top set in basic settings 099 which shuts down the lambda correction routine so eliminating the lambda correction system.

[Crasher]

I don’t know if it was me who closed this my mistake… I was a good way down number 2

[bobfrankish]

OK Crasher. Just found a thread going back to 2012 posted by dixie180. EXACTLY the same issue as me, unfortunately nothing ever posted to say he resolved it. You replied to him a few times. Anyway I have e-mailed him just for the hell of it, maybe I will get a reply, we'll see.

[Crasher]

Did you log a few Chanel’s to see what the signals such as RPM and ECU voltage did as it cut?

[bobfrankish]

Unfortunately, I only have VCDS Lite shareware (free) version which seems to have limitations as to what channels it can display. It only allows you to monitor measuring blocks 1 to 8. I can see RPM but not ECU voltage. However, if it is ECU supply voltage you are talking about, then that is the same electrical connection as the supply to the MAF sensor which I have monitored when the engine cuts and it stays constant at 14V or thereabouts with no fluctuation. Did you have a look at that old thread I mentioned? One of your replies says that you once had a car in your workshop doing the same thing and you never managed to get to the bottom of it! I'm sure the RPM will drop before it cuts as you can definitely hear the tickover go lumpy and falter just before it cuts. Weather not too bad today, so I am going to look at possible causes of it not firing straight away once it has cut. The other day, I took plug No.1 out, shorted body to engine block and looked for a spark whilst the engine was cranking and I could not see one. Maybe I was wrong, because I have made a good connection to the coil trigger input and there are definitely good strong pulses present whilst cranking, so there should be spark.