Club 80-90 Forums

WHY DO THEY FAIL AT THE START OF YOUR HOLIBOBS??!??.
20 Mins from home and the van died. Flashing glowplug light and total loss of power. Van limped very slowly clear of the dual carriageway. Will restart. Idles fast (1200 ish)and won't rev/no power. Glowplug light starts flashing again after 20 or 30 secs.
Had a fiddle with as many wiring connectors as I can see while waiting for recovery.
No surprise the cheap elms interface and phone doesn't spot any error codes.

Any bright ideas?

Sorry not a mechanic but taken from another forum, disconnect positive lead from battery for 10mins.
Also check brake light bulbs and wiring from alternator to ecu for damages.

When you say it won't rev do you mean when you press the throttle nothing happens? If so, that coupled with the 1200rpm idle indicates a fault with the throttle pedal. If I disconnect mine it revs high, thats what the MSA/EDC15/12 ecus do in response to a faulty throttle system.

Get yourself a copy of vag com lite (the free one) and read back the 'block' associated with throttle pedal feedback. It will tell you a lot about what is going on.

Dave.

I'll 2nd to what Dave's said

I'd left my throttle pot disconnected the other day after working on the radiator, started the van up and it was idling at 1200rpm,glow plug flashing and obviously no response from the throttle pedal

Switched off, plugged the cable back in and everything back to normal

Where is your throttle pot fitted and is there any damaged cables around?

Thanks chaps. Really helpful confirmation. suspected this or something related to air intake sensor but didn't want to bias the replies. Throttle pot is in the engine bay. Unplugged and replugged on the roadside but didn't try disconnecting the battery. Revs start to shoot v high (3k ish) for a fraction of a second after turning the key before they drop back to 1200. Might this be an invalid signal (chafed wire shorting??) rather than no signal.
I've got a few days to plan my next step as we somehow crammed 2 babies and 10 days worth of holiday stuff into a countryman - camping was only penciled in for a couple of nights of the break so no disaster.
I'm thinking maybe get a pot from a breakers to quickly eliminate the pot itself as the culprit.
Cheers again guys.
Jim

back home from hols now and have connected up with VAG com lite to read off the codes,
the throttle pot has an implausable signal intermittent code against it, however checking the value reaching the ecu from the measurment blocks it smoothly transitions from 0-100% as the pedal is depressed, pointing the finger of suspicion at....
00741 – Brake Pedal Monitoring....
Looking at the measurement group 6 block 2 i have 1-1-1 with brake pedal pressed and 1-1-0 with brake pedal released. am i correct that these fields are clutch sensor, brake sensor, brake light & that the middle 1 means the ecu thinks the brakes are being applied & cuts engine to idle.

Had the exact same fault on ours today. I couldn't read the fault codes and so a Google search on the symptoms threw this thread up.

Unfortunately the thread starter didn't come back with his solution, but using the useful information above, I cured our problem.

It turned out to be a bad connection between the potentiometer and the ECU.

Hope this helps others.

The 3 pedal switch inputs which must be wired correctly for the TDI to function as designed are F & F47, the two brake switch inputs which must switch at precisely the same time, and F36 the clutch switch input. The measuring block values with no pedals pressed should be all zeros, and should transition to 1 with the pedal pressed.

The inputs must be wired as follows:

F - brake lamp 'hot' side, the ECU will see earth though the bulb, changing to '12v' with the brake pedal pressed.
F47 - wired though a normally closed switch (pedal not pressed) to either sensor ground on early TDI's, or 12v (eg. current supply relay output) on late TDI's (check the wiring diagram).
F36 - wired the same as F47.

F & F47 are mandatory and will typically result in limp mode if incorrect. F36 is highly recommended, as the ECU uses this to provide smoother gear changes. It is mandatory if cruise-control is enabled.

That is all.