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VW Polo dies accelerating

I recently took my 1991 1.3 Polo to my local (non VW) garage as it had begun to overheat after a very brief run. I drove the car to the garage (about one mile) and, despite the short distance, the car was driving fine. I was informed the overheating was 'just due to a loose connection' for which I was not charged. On leaving the garage the car began losing power under acceleration (particularly in first gear), resulting in me having to drop down gears and/or attempt to drive at a consistent rev level. Dropping down or decelerating resulted in the car picking back up again. In addition, moving off from a standing start was almost impossible resulting in me having to slip the clutch whilst maintaining consistent revs. Despite this on a couple of occasions it just stalled. I took the car straight back whereby the mechanic drove the car and agreed something was amiss.

I have now been informed the problem is 'probably the ECU'. The car was sent to a local electrical auto specialist who could find nothing wrong with any electrics other than to suggest the above. The car has recently had a new distributor (circa 12 months ago) which I am told has tested OK as have the other likely mechanical 'culprits' (I write this as someone with little knowledge of engines). The garage has suggested they source a second hand ECU assuming they can find one to match to check if this is the problem.

Aside from the overheating - which only happened once and was not severe - the car is generally solid and had been running perfect prior to taking it in. From a layman's point of view it appears that the problem has resulted from something which changed whilst in the garage but I'm willing to accept it may just be a co-incidence. I'm happy to stump up =A350 for a second hand ECU but would appreciate your views on the likelihood of this being the problem. Finally, I drove the car back from the garage prior to the weekend and it was performing better than when I first reported the problem - although it wasn't great it didn't come close to stalling.

I appreciate, even as a layman, that it could be a number of things. However, would an ECU problem result in varying performance or would you expect to see the same'ish problems whenever it's driven? I've had the car for many years so if you need any more info please ask.

Many thanks

Reply to
mark.leason
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There's lots of things it could be. The ECU would be way down my list. Things to check/have checked:

  • Distributor- especially the hall sender. Quite a common failure. I think the bearings get a bit of play in, and then the vanes in it hit the hall sender.
  • Fuel pump/fuel filter

  • ignition amplifier

  • Distributor cap, HT leads and plugs

  • Fuel injection unit (I'm guessing this is single-point, not multi-point injection)

  • Have the timing checked. It shouldn't have got disturbed, but I've seen a few come back from garages with it way out of wack.

How well does the car idle? Is it smooth and even, and just lacking in power when you try to accelerate?

Any obvious loose wires?

Reply to
Chris Bartram

Or air leaks.

Reply to
Duncan Wood

Thanks Chris

I'm not a mechanic by any means but I was sceptical of the ECU. Re your question the car idles OK. It's only under acceleration that it struggles. I started it on the drive the other day and I struggled to get it moving (on a flat road) without it dying on me. I managed to slip the clutch enough to the point that I could eventually release it fully and then coax it up a bit. When I bought it back from the garage it was fine pulling away other than the odd judder but then it started dying again under acceleration. Not sure if that helps but in summary it's not consistent. The only consistent thing seems to be that if you 'floor it' it has the reverse effect!

Reply to
mark.leason

It happens that snipped-for-privacy@tesco.net formulated :

I would try a new fuel filter then perhaps a new coil or ignition module. A filter can block itself up quite quickly, especially with a tank of dirty fuel.

Does the exhaust note sound normal? Might be the internals of the CAT breaking up and obstructing the flow.

ECU would also be at the very bottom of my list.

Reply to
Harry Bloomfield

I'd say its not the ECU but that the ECU has sensed a fault and gone into limp home mode.

Reply to
Chinese Cracker

A very good point. Polos of that age have a weak point where the fuel filler meets the main tank. Like many VW cars of the time the filler is in the wheelarch and takes a bashing. Unlike other VWs, it's one piece with the tank. Anyway, it rusts. Usually it leaks, but there could be a load of rust and s**te in the fuel. I've never looked where the fuel filter is on a 1991 car- SWMBO had a Polo but it was a bit older, and pre fuel injection.

Reply to
Chris Bartram

Thanks all. I'm going to find an independent VW dealer - I'm not sure a main dealer will be worth the cost given how much the car's worth - and I'll be armed with a bit more knowledge. It certainly drives like it's starving of fuel so thanks for that.

Reply to
mark.leason

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