Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing 3.9 v8 cuts out at bottom of a hill

No misfire. I had a look at the throttle body and maf earlier and it all looks pretty clean, from what I could see in the idle control valve hole that’s pretty clean but I haven’t sprayed any cleaner in.

One thing that’s vaguely confusing me, it may be a red herring and I can’t find an answer on google, is that of the stepper motor fix articles I’ve looked at there is no washer on them. The original in my car had a metal washer and the Lucas a slightly thicker fibre one. Has anyone else got a washer on there’s, and if not could the additional distance out be a part of the prob?

Is this +8 new to you and this problem has been from when you first drove it or was it running OK and then started? If it was running OK and has now just started then the washer won't be the issue, my Stepper Motor has the fiber washer.

I am still leaning towards the Road Speed Sensor not working correctly.

Now you have confirmed that the issue occurs when 'on the flat' my money remains on the speed sensor. If you connect notebook PC and RoverGauge to the diagnostic socket and go out for a drive you should see the road speed indicated under the 'Tune' tab.

I would change the MAF just because it looks clean doesn't mean anything. I had a similar problem on an Alfa Spider, cleaned the MAF no change, changed the MAF and all good.

Well all fingers crossed the problem may be solved, the base idle was way out, and I’m guessing because the car came from a flat part of the UK, unlike the steep hills here i. Cornwall, the stopping on over run had never been an issue.

Two test drives now, tonight’s was particularly pleasurable in the evening sun, and all seems good.

Thanks for all the comments everyone, I genuinely have enjoyed the learning process this opportunity gave me.

Glad to hear things are looking "normal". So what was it idling at, and what procedure did you follow to reset the base idle?

Very simple to do.

Locate the Allen bolt adjuster on the top of the throttle body.

Get the car warm then whilst on tickover clamp the hose on the right that goes from the throttle body to the plenium chamber.

At this stage the car might cut out, like mine barely idle, or if it sits nicely at 600rpm it’s ok.

If you need to adjust make sure you have a pen and paper to note your adjustments so that if it all goes wrong you can return to original setting.

I used a T handle Allen so I could accurately measure half turns which to open the air screw is anti-clockwise. Mine was three half turns.

Apparently you need to watch for the fan kicking in as this affects the rpm when you are trying to set it.

Hope that makes sense.

Reduced idle speed when fan kicks in would be down to the increased alternator load as it attempts to match the current drain from fan motor.

Photo? Interested in this. Thanks

Good to know you got this sorted out Gavin, and that you can roar about in your "new" V8 with confidence. Good write up too..