sudden, momentary loss of power

[fetyaddi]

Hi all ... My 96 Chimp suffers from random bouts of complete loss. I'll try and explain it as best I can, but I'm at a loss as to how to fix it. All help appreciated.
They happen randomly [any revs, any gear, any temp, any speed], and feel just like everything has shut down [ie: more severe than just taking my foot of the accelerator], although power is still coming through [lights/fuel pump still on].
The best way i can describe it is this; if I'm cruising at a steady 80, and it happens, the car speed will start to drop. If i put my foot down, power is restored immediately, and the car will accelerate with a jolt. If I dont move my foot at all, the car speed will drop to maybe 70 [a guess], then power will suddenly come back in, and the car will accelerate up to 80 again.

All in all, quite bizarre ... Any ideas ?

[Plotloss]

Did the car have less than a quarter of a tank in it when it happened?

Mine used to do this on left handers as speed when there was less than a quarter of a tank in it...

Something to do with the fact that the fuel outlet is front left so when you go around left handers all the fuel gets washed to the rear right.

[fetyaddi]

Nope ... I have plenty of fuel, and it happens on the flat [I do a lot of motorway driving]

It can also not happen for days [poss. weeks] at a time

[GreenV8s]

A worn throttle pot can cause exactly those symptoms. There are some other faults that could too, but the throttle pot would be my first guess.

[fetyaddi]

Is there an easy way for me to tell if that's it ... [translate this as "I'm stoopid - where's the throttle pot"] ?

[GreenV8s]

If you disconnect it, connect an analogue multimeter to measure the resistance, and move the throttle through the full range of positions, the resistance should change smoothly throughout the whole range. If it doesn't, it's faulty. This won't pick up all faults so you can't prove the pot is good, but sometimes you can prove it is bad (iyswim).

[soddy]

Could be the throttle pot but I would have thought that would be less noticeable than a 'total' loss of power ... sounds more like loss of spark or injector ... there is an injector signal feed off the negative coil post .. make sure that is not damaged or loose .. check all earth connections, straps and the injection system ones that bolt onto the inlet manifold .. could even be the distributor amplifier playing up.

[GreenV8S]

soddy said:

Could be the throttle pot but I would have thought that would be less noticeable than a 'total' loss of power

I can confirm that a knackered throttle pot can lead to a total loss of power (and consequent sudden engine braking) for several seconds at a time.

[chimtvr]

throttle potentiometer lives on the throttle body on the plenum (follow the throttle cable)on the opposite side to the cable a little black unit with three wires going off to a plug you cant check it with resistance very well you need a multimeter and back probe the plug (with it still plugged in and ign on) i cant remeber the colours but one wire should give +12v another should be a good - and the last should be at about .8v then as you pull the throttle back to full it should SMOOTHLY rise to 5v
hope this helps

[mrb_74]

I'm having the same prob too at the mo, but sometimes i'm brought to a complete standstill. It only happens when i'm on the motorway too, is that the same with you?

Its going into the garage tonight to be checked out so i'll let you know the diagnosis when they identify the problem!

[GreenV8S]

mrb_74 said:

I'm having the same prob too at the mo, but sometimes i'm brought to a complete standstill. It only happens when i'm on the motorway too, is that the same with you?

Does it tend to happen say 20 minutes into a journey, and miraculously fix itself after ten minutes or so? These are the initial symptoms of a failing fuel pump relay. If it is the relay, you'd also find that the fuel pump doesn't prime when you try to start the car. But on a motorway there'd be too much noise to hear that.

[wightman]

This problem is very very similar to mine. I would also be very interested to know if anyone has found a fix to their problem. I am going to change the leads for magnecor ones and fit new plugs as a start.

[victormeldrew]

Mine exhibited similar symptoms when the coil was on its way out. You could also check the condition of the leadfrom coil to dizzy, and problem there woule lead to total loss of sparks.

[Mr Jenks]

I recently experienced very similar sounding problems with mine, although it had no link to the temperature as it would hapen after an hour on the motorway, 20 yards from home on a frosty morning or in the middle of the M25 roadworks. The connector to the ignition amplifier was corroded and had contaminated the module itself. New connector, terminals and amplifier with no trouble for the last 3 months.
Now wait till i go out later, no prizes for guessing what is bound to happen.
Dave