What's the likely cause of this?

[Jurgen Schmidt]

I think this YouTube video highlights my symptoms best....

(Video is of me about to put her in the garage after a 37 mile trip)

https://youtu.be/byt-KSbh-o8

She only seems to do it when I'm stationary or approaching a stationary position, so for example pulling up to a junction, but she doesn't do it all the time though

Obviously, this can become a problem for me in traffic

Edited by Jurgen Schmidt on Thursday 21st July 22:27

[Milky400]

Stepper motor,

[Jurgen Schmidt]

Milky400 said:

Stepper motor,

Thanks. This has only just been replaced, as a probable cause, but the symptoms still persist

[mrzigazaga]

Jurgen Schmidt said:

Milky400 said:

Stepper motor,

Thanks. This has only just been replaced, as a probable cause, but the symptoms still persist

Hi.

I have a friend with a 5.0ltr HC Griff lump in his Wedge and he always re-calibrates the stepper motor with rover gauge whenever he replaces it..I believe this needs to be done after replacing...There is also ECU-Mate....Just a thought....Cheers...Ziga

[ChimpOnGas]

Jurgen Schmidt said:

Milky400 said:

Stepper motor,

Thanks. This has only just been replaced, as a probable cause, but the symptoms still persist

You need to consider the stepper motor is just a dumb unit controlled by the ECU which in turn is only trying to do the right thing with the stepper motor based on the information it's gathering from various engine sensors and the road speed sensor.

Once you've understood how the whole system works you'll quickly understand why just replacing the stepper motor failed to resolve the problem.

Personally I would start at the beginning, and that means making sure your base idle & throttle position sensor are correctly adjusted as per the book, there's an excellent and very complete guide here:

http://www.actproducts.co.uk/2011/lucas-14cux-fuel...

Once you've followed the base idle and TPS settings and you're confident these elements are as they should be you can then look at the ignition side. Ignition faults are super common on Chims & Griffs for a host of reasons and I cant stress enough every element needs to be in tip top condition to achieve that perfect idle.

Start by replacing the utterly inappropriate shrouded electrode and rated too cold NGK B7ECS with a set of NGK BPR6ES or better still NGK BPR6EIX iridium plugs, both will immediately clean up your idle nicely over the B7ECS chosen by TVR.

Next up is to delete those dreadful plug extenders which are probably the cause of 90% of all ignition faults on these cars, in addition to switching to the above plug types... deleting the plug extenders is one of the best things you can do to improve the reliability and performance of your ignition system. Just make sure you protect the ends of your HT leads properly as the manifolds on Chims and Griffs are such that protection of some sort is essential.

http://www.pistonheads.com/gassing/topic.asp?t=143...

Finally you need quality ignition leads, and if you want the best you absolutely must try a set of MSD Super Conductors.

Trust me, I've tested the lot on my LPG wasted spark Chimaera running 40kv MSD coil packs... and the only HT leads I'll entertain are MSD Super Conductors, if MSD Super Conductors can survive on my TVR, you can be sure they're the best you can get!

If after all the above your car does not idle super sweetly I will eat my hat, if it still presents the stalling issue you have a sensor fault (most likely), or an ECU fault (less likely). You can of course clear an ECU fault code by disconnecting and reconnecting the battery but you are much better off using Rover Gauge to try to identify the rout cause of the problem.

Good luck with it, whatever the situation all Chim and Grif owners should seriously consider the all ignition enhancements above.

You will definitely feel the difference

[andy43]

As above - check base idle's right (squish pipe flat, idle screw to adjust base idle to 525 rpm), and check throttle pot is telling the ecu your foot's off it (needs rovergauge, ecumate or a voltmeter to check it's giving the correct voltage). Make sure it's consistent and repeatedly gives the same or very close idle voltage. Or it could be a chinese stepper that may need an extra washer as the plunger bit is too long.
Another good guide here http://ecumate.com/docs/Ecumate%20inst.pdf

[FFMan]

bit left field this one but I had a problem that isn't so different

turned out to be the clip in the dizzy that stops the main dizzy shaft rising was bust, and every now and then the dizzy shaft would lift and knock the carbon brush in the cap up, thereby disconnecting the HT for a second. the near stall would allow the shaft to drop back into place. only happened at idle for some reason.

was a bugger to find and I can't claim the credit for finding it.

[Jurgen Schmidt]

Thanks for the suggestions guys!