Rev counter gone crazy and juddering

Recently, when driving the engine judders, wants to stop and the rev counter goes up & down like a yo-yo. Like as if the car wants to cut out.

I hit the accelerator and the revs stabilise after some more juddering. Used to do it when cold but now when warm.

Any ideas? HT Leads? Lift pump filter?

check the earth from the rocker cover, chase it back through the loom as its prone to cracking and if thats not on the dials go mental

Checked the earth on the rocker cover. Looked loose/weak so re-made the connection. But the rev counter still drops.

Don't think it was the earth connection.

Getting worse now. Does it at standstill……

Turn the car ON. Rev the car to around 2000, hold it there and suddenly the revs drop, engine wants to cut out, then suddenly the revs pick up to 2000 again for a little while and then the revs drop again (repeats itself). If I don't hold the accelerator pedal then the engine stops. I need to hold the accelerator pedal for the rev's to pick up again.

Sounds like the fuel is momentarily cutting off? Checked the dizzy and looks clean. CIS faulty? Think the rev counter is OK, the rev counter is a sign of another problem…….

if the rev counter doesnt seem to match what the engine is doing it could be a faulty hall sensor in the dizzy

I had the same problem I replaced the ignition coil (12v) cleaned all the terminals and it hasn't done it since.

vw_mk1, I'm having exactly the same problem.  I took it to a VW specialist who said the mixture was 'horrendously' weak.  They corrected it and it seemd fine.  However I'd had a mobile krypton-tuner around 6 weeks earlier, so I questioned how it could have got so far out-of-whack so soon - they couldn't give me an answer.

I've had it back 2 weeks now and driven it twice - guess what, problem has returned!

Suggest we keep each other in the loop.

Hey Minty - I'm on the case this week. Was fitting a new water pump over the weekend.

List of things I'm gona try;

1. Connect fuel pump to ignition live. Will prove if the fuel pump is cutting out.
2. Clean the 3 pin connector contacts near the dizzy. Aparently the red/white wire goes to the rev cntr.
3. Fit a new ignition coil.
4. …..

Mine only started to do it when the rainy season started. Was fine all summer. Hoping its damp leading to corrosion on contacts somewhere.

3) no it doesn't, the dizzy wires go to the TCI-H unit. the rev counter wire is the red/black to the coil. Worth cleaning dizzy plug tho as if the hall sensor or wiring fails this is the kinda thing that will happen.

worth cleaning up the rev counter connection too, as this feed also triggers the fuel pump relay.

Did the following;

1. cleaned 3 pin contact on dizzy…. no difference
2. cleaned dizzy internals…..no difference
3. cleaned TCI unit contacts and replaced the HT lead from coil to dizzy… WORKS now.

coil lead to dizzy looked dodgey. Had corrosion.

awesome