Audi 100 2.2 - Poor running when hot?

Retrorides · 21-03-17, 01:42 PM

Hi All,

I am suffering issues with my 1987 Audi 100CD 2.2 Saloon. When I bought it the car had not been used for 10 years and so it was treated to a fuel tank drain, removal, fuel pump replacement, new fuel lines and fuel filter amongst brakes etc for the MOT.

The result now is the Audi is fine when cold and runs well but as soon as it gets warm it suffers from hestitant running and stalling. Swicth it off and turn on and it will go again a few feet but leave until cold and the problem has gone??

I have replaced the new fuel pump with yet another new fuel pump and bypassed the accumulator but still the tank pump is buzzing despite having half a tank of fuel (although it only buzzes when warm)

In additon it has had a full service with new leads, distributor and rotor, plugs, air filter another fuel filter, camb belt and vacum hoses?

I am running out of things to try now? If you have any ideas or can recommend someone who can look at the injector pump it would be appreciated? I am new to Audi's and always remember these when I was growing up and love it when it runs well.

Hopefully someone can help?

Thanks

maxustaxus · 22-03-17, 07:43 PM

Hello,

I wonder, have you checked the Digital Idle Stabilizer? I am not sure how this is done, but I guess it is possible that a problem with this unit is being disguised while the engine is cold because of the cold start system. But when it is warm then the hunting and poor idle is on show.

I am not too sure about C3s, so this is just a thought.

Ringmaster · 22-03-17, 08:21 PM

Try removing the Idle Stabilization Valve, sprays loads of carb cleaner into it and refit.

It may work.

Retrorides · 22-03-17, 09:38 PM

Thank you both very much for the tips. So far the sensors have been checked with a multi-meter and it seems to point back at the fuel pump again? I shall definitely check out the items mentioned and maybe try and return the second pump I purchased and installed last week.

Best.

ovalking · 22-03-17, 11:04 PM

The buzzing fuel pump seems a bit odd. Mine makes more of a whine, and you can't hear it when engine running.
I wonder if it is under excessive load for some reason. Have you done a fuel delivery test? I don't recall the litres/min figures but it's a lot.
Maybe it's the power to the pump that's the problem. Any buzzing when the fuel pump relay is bypassed? (Position 10 in the fuse box).

Retrorides · 27-03-17, 12:43 PM

Hi,

Thanks for the tips on the fuel pump relay. After some further checking the fuel in the tank is looking orange again so the fuel tank has been removed and is with a company being refurbished. I just hope they manage to get it sorted and I am waiting for them to call me today.

The only other item I need are the rubber damper/bushes that hold the fuel pump in place. These have perished teriibly so does nayone have an idea of where a new set could be bought (3 in total)?

Thanks again :0)

22-03-17, 07:43 PM	#2
maxustaxus Grown up member Join Date: Mar 2010 Posts: 198	Hello, I wonder, have you checked the Digital Idle Stabilizer? I am not sure how this is done, but I guess it is possible that a problem with this unit is being disguised while the engine is cold because of the cold start system. But when it is warm then the hunting and poor idle is on show. I am not too sure about C3s, so this is just a thought.

22-03-17, 08:21 PM	#3
Ringmaster Senior Member Classic Audi Club Member Join Date: Apr 2008 Posts: 1,326	Try removing the Idle Stabilization Valve, sprays loads of carb cleaner into it and refit. It may work.

22-03-17, 09:38 PM	#4
Retrorides Newbie! Join Date: Mar 2017 Posts: 11	Thank you both very much for the tips. So far the sensors have been checked with a multi-meter and it seems to point back at the fuel pump again? I shall definitely check out the items mentioned and maybe try and return the second pump I purchased and installed last week. Best.

22-03-17, 11:04 PM	#5
ovalking Grown up member Classic Audi Club Member Join Date: May 2009 Location: Ipswich Posts: 270	The buzzing fuel pump seems a bit odd. Mine makes more of a whine, and you can't hear it when engine running. I wonder if it is under excessive load for some reason. Have you done a fuel delivery test? I don't recall the litres/min figures but it's a lot. Maybe it's the power to the pump that's the problem. Any buzzing when the fuel pump relay is bypassed? (Position 10 in the fuse box).

27-03-17, 12:43 PM	#6
Retrorides Newbie! Join Date: Mar 2017 Posts: 11	Hi, Thanks for the tips on the fuel pump relay. After some further checking the fuel in the tank is looking orange again so the fuel tank has been removed and is with a company being refurbished. I just hope they manage to get it sorted and I am waiting for them to call me today. The only other item I need are the rubber damper/bushes that hold the fuel pump in place. These have perished teriibly so does nayone have an idea of where a new set could be bought (3 in total)? Thanks again :0)