[s-cars] Need time for S4, help me fix my 200!

[Rich Assarabowski]

Went through the car again today, pulled the turbo hoses, sprayed ether
on vacuum lines and injectors, no leaks apparent.  Pulled the O2 sensor
from the 200 and instlled it in the S4 (they have identical ones, what
luck!), works fine in the S4, no problem, so I put it back into the 200.
Pulled out the airbox, replaced the air filter, checked the lines to the
carbon canister and decel valve, everything looks fine.  Plugged line to
decel valve to make sure it's no leaking, no difference.

The clue to this puzzle is that when the engine is cold, it runs
perfectly for a minute or so before it starts breaking up.  Even though
there are no fault codes displayed, could it be some kind of electrical
thermal problem (distributor, coil)?  A scope would tell for sure.
There's still a chance the injectors are faulty, even though they looked
good when cold, I hate to spring for 5 new injectors to find out,
though...   I've pretty much ruled out a vacuum leak at this point.

-- Rich Assarabowski


>From: Charlie Smith [mailto:charlie at elektro.cmhnet.org]
>Sent: Sunday, September 29, 2002 5:04 PM
>To: Rich Assarabowski
>Cc: Audi S Car List
>Subject: Re: [s-cars] Need time for S4, help me fix my 200!
>
>
>Earlier, Rich Assarabowski wrote:
>
> Not strictly S-car related, but the sooner I fix this one the more
> time I'll have for the S4!
>
> My 1990 200q suddently started running poorly.  Engine runs fine when
> cold for about the first minute, then idle becomes very rough,
> stumbles at the slightest application of the throttle and has very
> little power, car is barely driveable.
>
>>Make sure you don't have an air leak after the air flow sensor
(flapper plate assembly), before the throttle body.
>>
>>On the 5kCSTQ the blowby hose which goes from the lower left side of
>>the block up to the intake manifold is prone to develop a split on the
backside - and it causes similar symptoms.  But, >>since your idle is
fine I assume the leak in in the intake before the throttle body.
>>
>>If your O2 sensor system is working OK, it should correctly richen the
mixture to compensate for the leak ...  After
>>you've held the throttle steady for a second or so.  If the problem
diminishes after a second or two
>>of steady state throttle, this also points to an intake system air
leak. The symptom "stumbles at the slightest
>>application of the throttle" sounds
>>like this is what's happening.
>>
>>    - Charlie