idle's and then dies

[adyw]

Gents,
I have had an issue with the Griff today and I need an opinion before I start buying expensive new parts.
The Car 97 500
warm or cold, idles at 1000rpm then suddenly dies and stops.
First thoughts stepper motor, Has been removed and cleaned, no effect.
Second, idle speed screw in plenum adjusted, no effect
Third as the bible says reset the ECU, so unplugged, no effect

Finaly started the car and then unplugged the stepper motor electrical connection, It's running fine. A little high idle 1100rpm, but apart from that fine.

So the question is am I right in thinking new stepper motor ?
I have compared it to a friends stepper and I believe the motor valve part is further out on mine than his, So could it be defective.

Advice please

[GreenV8S]

adyw said:

warm or cold, idles at 1000rpm then suddenly dies and stops.

Does the fuel pump stop before or after the engine dies?

Stick a passive strobe light on #1 HT lead and see if the spark dies before the engine stops.

Similarly put a test lamp (or NOID diagnostic light if you want to be posh) across one of the injectors and see if the injector signal stops before the engine dies.

You can completely eliminate the stepper motor from the equation by unplugging it while the engine is idling steadily, but from these symptoms I don't see any reason to suspect the stepper motor has anything to do with it.

[adyw]

Thanks,
will do, I have a strob for the HT leads.

[adyw]

Right tryed that,
Spark seems to stop as engine does,
It runs fine from cold for around 5 minutes and then it begins,
I did check the stepper again and it must be moving at it has extended.
But runs fine with out the stepper connected, well thats what I thought, I've just also run it with the stepper disconnectd and it also suddenly stopped.

HELP no idea now

[GreenV8S]

adyw said:

Spark seems to stop as engine does,
It runs fine from cold for around 5 minutes and then it begins,

If the spark stops before the engine then that explains why the engine is cutting. The most likely suspects are ignition amp, coil, dizzy pickup. The easiest way to test the amp is by substitution.

[spend]

I read of a test somewhere, that described testing the amp by flicking the rotor arm, think I posted a link...

Dave

[GreenV8S]

spend said:

I read of a test somewhere, that described testing the amp by flicking the rotor arm, think I posted a link...

Dave

I can see the theory, but how effective would this be at diagnosing an intermittent problem that only happens when it's hot?

[adyw]

I don't think the spark is failing before the engine, is almost together, well as best as I can tell, The rotor arm and dixxy cap and coil are all relativly new

[spend]

GreenV8S said:

spend said:

I read of a test somewhere, that described testing the amp by flicking the rotor arm, think I posted a link...

Dave

I can see the theory, but how effective would this be at diagnosing an intermittent problem that only happens when it's hot?

I think the measurements (V / R) specced when it was sharged??? Agreed though, I keep a spare just in case

Dave

[GreenV8S]

adyw said:

I don't think the spark is failing before the engine, is almost together, well as best as I can tell, The rotor arm and dixxy cap and coil are all relativly new

If the spark fails, the engine will stop immediately. The point is that if the spark continues while the engine is spinning down, you know the spark isn't the cause.

[adyw]

right,
tried new coil same effect gets to around 60'c and then cuts out
One thing to note from stone cold start, it semi starts e.g splutters at 600rpm plus a high pitch wissle through exhausts and then stops, Second start lots of right foot start fine. I am starting to think fuel pump ?
I recently took the tank out and had it cleaned ( I had a leak)so I know there is no slime in the tank, plus also had to replace the fuel pump relay as it went.
Could be fuel pump ?

[Fat Griff]

Try looking for any induction hosing thats lose or perished, there is also a vacumn pipe underneth the plenum/throttle linkage that could of dropped off. Try disconneting the afm see if it run's any different. Otherwise borrow somebody's ignition see if it runs better! Good luck!

[adyw]

Got a ECU fault reader on hire, it is telling me code 45 which is offside lamba sesor out of rang, So I though fuel, So let her get cold and took cylinder 1 and 8 spark plugs out and they are black as black can get, So Spoke to Dulfords and they agree with me it is over fueling, new sensor required.
The fault has got better, it now runs longer without stalling, but it does struggle, 1000rpm and then get dragged down to 800rpm exhaust wissles and then it kicks up again, but sometimes it just drops completly.