Audi 80 1.8s 1986 intermittent lack of power problem

Hi,
I have a 1986 Audi 80 Sport 1.8 injection engine, as of last year it has had a very intermittent problem.
The problem is that the engine seems to have absolutely no power if
you put your foot to the floor it just has no grunt. I've had to pull over when it has happened on motorways and when you get off the throttle it manages to stall itself it has so little power. We suspect it could be a fuel supply problem as there is no miss-firing, that i would expect with a spark plug problem. We've gone though and check all the fuel pump connections but they all seem ok. The strange thing is that is is a very intermittent problem it happened once a year ago, about 1.5 months ago and 1 week ago. The only slight pattern is that it has been running for a bit in stop start traffic, the problem then occurs a little while after getting going again. All the dials are normal and it is not running very hot.
Once you stop the car and re-start it it is fine, although it can start the cycle again after a few miles but not every time. The fuel take is not running on dregs either but as we thought it was a fuel supply problem we did top it up with high octane fuel after each occurrence as it was fine after that, but that could also be as it was stopped for a little while too.
We've also tried disconnecting the vacuum tube that changing the timing at higher revs to see if it was that but it made no difference.
Does anyone have any ideas for experienced this problem in the past?
Many Thanks,
Richard
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Fuel Pump Relay?
Not sure of common problems on the A80, but on my A100 the joints on the relay pcb were cracked. Resoldered.... and had no problems since....
G.
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Could there be a loose baffle in the exhaust? I had one in my Passat and it literally killed all power when it closed off the exhaust flow.
Someone already mentioned Fuel pump relay Bad or loose fuse in the fuse box. It is usually an unmarked fuse that some people think is a spare fuse. I have seen many Audis where they had been removed but the owners wondered why they engine was having problems and the shops could not find the problem. 8^o Oxygen Sensor wiring Bad Ign Distributor Rotor. I ONLY use Bosch rotors!!!! Weak ign coil Clogged strainer filter to the fuel pump, if so equipped.
OR.................................... Debris in gas tank that floats over to the pickup causing a no-fuel problem. When you turn the engine off the vacuum is released and that debris gets released. Maybe an inner foil from a Gas Treatment bottle.
JMHO and some ideas! ;-)
--
later,
(One out of many daves)
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dave AKA vwdoc1 wrote:

I would suspect the debris in the tank that Dave suggested. Some of the Audi's from that time had a plastic coating in the tanks that degraded over time and caused this type of condition.
Open the tank when it is low on fuel and clean any particles with a rag.
Another fix that Audi suggested was to cut the pre-filter off the fuel pump which causes the debris to be caught in the fuel filter. Change the fuel filter several times in the if a performance problem occurs and then the problem should not occur again.
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On Jul 4, 5:24 am, TonyJ <"tonyjnospam at nospam visi.com"> wrote:

Thanks for your suggestions guys,. I changed the fuel filter a few weeks ago which didn't instantly solve the problem, unless as you say it is getting clogged up again. I really hope its not debris in the fuel tank though as if they have got into the injection system then i would suspect it would have wrecked it by now.and make the problem much more regular. Unfortunately i don't think there is a way into the fuel tank, its a sealed plastic unit so i am not sure how i would get inside i can try looking in but i don't think i will see much.
As for the fuel pump relay that was our first thought but its very strange for it to be such an intermittent problem with a relay like that.
Thanks for all your ideas though i will look into as many as i can.
Richard
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On my '83 Audi 4000S I have a pre-filter before the fuel pump AND a fuel filter (2 filters). I thought your '86 would also have a pre-filter but you say you changed it or are you saying you only changed the main fuel filter? I usually can hear an external fuel pump strain as it can not get supplied with enough fuel. It gets louder and whines noticeably.
You look inside of the fuel tank CAREFULLY (explosive gasses) with a mirror through the sending unit hole. This would be a rare problem but when you rule out all other theories..............(Sherlock Holmes) My Audi A4 AND my '83 both required fuel pump relays for either starting issues or dying out issues. The relay was a cheap test which was well worth it since I HATE to be stuck with a non-running vehicle. <g>
SO CHANGE THIS FIRST!
JMHO
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(One out of many daves)
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