Random Spluttering

[Darren Groves]

So over the winter period the Herald was completely rewired from scratch and the old Ford EDIS & Coil Pack were replaced with a VW Coil Pack. No major issues and the car has been driving absolutely fine except for a random splutter every now & then. Doesn't do it every journey, but it will do it on most, just for a few seconds and then rights itself and it will be fine for ages after. I've been kind of ignoring it a bit as it wasn't causing any major dramas, but thought I'd do some investigation.

As the only real change to the EFI setup was to the ignition side I swapped out everything that was new, HT Leads, Coil Pack & Plugs, but the problem was still there, so decided to buy the full license for MegaLogViewer to see if anything would show on there. The screen shot below @ 268 seconds shows the RPM & Spark Table with some odd spiky readings, tbh I don't really understand what I looking at totally, but certainly doesn't look right to me.....any ideas what this is telling me and what would cause this?

Thanks
Darren

 

[Nick Jones]

You are loosing your rpm signal briefly.  Suspect crank position sensor or its wiring.

Nick

[Darren Groves]

12 hours ago, Nick Jones said:

You are loosing your rpm signal briefly.  Suspect crank position sensor or its wiring.

Nick

I’d come to that conclusion, so good to have it confirmed.

Thanks
Darren

[Darren Groves]

New crank position sensor fitted and all is good with the world again....

 

[Nick Jones]

That's good.  Data logging is good for diagnostics - and not just on cars.

Nick

[rogerguzzi]

14 minutes ago, Darren Groves said:

New crank position sensor fitted and all is good with the world again....

 

Hello Darren

                      Was it a genuine Ford one that failed?

I had a similar problem last year when setting Microsquirt up one sensor would not let engine rev over 3500RPM

Roger

ps I have 3 now! when I get the new engine fitted and running I am going to try them all and bin any that are suspect(they are only about £10)

[Darren Groves]

Hi Roger,

It was supplied by Trigger Wheels, can’t recall who the manufacturer was, it was the one from my original Megasquirt installation, so probably done 15k miles or so. The original one supplied by TW was dead on arrival.

Will get another spare.

Darren

 

 

[Nick Jones]

The genuine Ford ones are pretty durable but do fail occasionally.  I remember a neighbour with CVH Sierra, which suffered the exact "random spluttering" you described for 18 months or so, resisting diagnosis by several garages.  Eventually it declared itself by flatly refusing to proceed one morning and the AA man diagnosed it.  This was before I'd starting messing with EFI, so although I'd figured out it had no spark I had no idea what to suggest next!.

I think the one on the Vitesse is my original Ford scrapyard rescue one from 2004 or so.  I bought a matching spare (Intermotor on the box) which ended up on the PI and was replaced in the spares box by another Intermotor one.

Nick