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Idles ok - then cuts out

Scamper

Scamper

New member
Hi, now that my ABS ECU has been replaced (ebay bargain) on my 90 C4 it seems that another fault has taken over as my main reason for not driving the car.....
Over the last couple of days I have experienced a slight hesitation on part throttle and then yesterday whilst on the motorway (lane 1 thankfully) a complete loss of power and engine shutdown - twice in 30 miles. Bit scary, but once the lights all came on I could bump/restart the car and get back home.

Now, i have cleaned the ISV and AFM (does the afm need to be resealed after opening??), tied off the wiring harness as per the STB, the O2 sensor is bypassed so is not connected (was running fine like this before).
Could the ABS ecu be causing this??? I am inclined to think not...but not sure.
Any other quick tests I could perform to isolate a faulty component?

Maybe the car is having a mid life crisis having just gone through 100K!!!
 
if its a hard cut-out (rather than a spluttering slow death) do you have an immobiliser?.. could be its on its way out; i've had two fail on me in similar ways in the last 5yrs (neither time on a porsche) and so am overly suspicious of the bloody things whenever something like this happens [;)]
 
smallspeed - its a sudden cut out. Very abrupt, no coughing or spluttering. it does have an immobiliser fitted with one of those proximity fobs to disarm the system.... I will have a look, thanks
 
just had a look at the coils;
unplugged the coil towards the front of the car - car started and ran fine

unplugged the coil towards the rear of the car - car started but ran rough

is this an indication of a bad coil? should the car run equally well on either coil if one is unplugged??

ETA i have replaced the distributor belt a while back and its fine
 
yes would seem to suggest something odd - the car should be the same - sounds like a bad plug/lead. Possible it is the coil - I can't recall if there is room to switch the leads so the coils swap. If that was the case then it would be easy to spot if it is coil or other.
 
my guess would be the immobiliser too for a sudden complete shutdown of everything. Only other possibility is the ignition switch and connector.

If its misfiring on one coil it would suggest a plug or injector at fault
Don't know anything about these beasts but I would start the car and then on idle remove one spark plug lead at a time (insulated pliers) and then put it back on the plug.The one that has no effect on the engine speed has a fault associated with the lead/injector/plug etc
 
Dodgy DME relay leading to the fuel pump being cut off? I know this is more associated with the car not starting at all but might be worth a look at?
 
as I understand the problem Steve it is a complete shut down of all electrics as if you had switched off the ignition key whilst driving along.
 
Steve, I have a spare DME and swapped them over...no difference.

I can hear some clicking in the engine bay on the left hand side as you look in, so I am thinking its ignition related i.e. bad coils, ignition lead.

it was serviced 1500 miles ago so i dont think its the plugs.
 
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