[urq] Intermittent stumble

[Eric Renneisen]

Could it be a sticky metering plate like Ingo found last year?  The
relevant post is below.

Eric R.

> I decided to look at the airflow metering plate again, 
> which I initially thought was binding, and compared it 
> with another that I had just recently bought.  What I 
> discovered was that it was not sticking against the 
> venturi wall, but rather that the pin that rests on the 
> leaf spring had actually worn a hole in it!  On decel, 
> it would essentially stick, the pin lodging itself into 
> the hole, choking off air and fuel.  It would not 
> restart unless I turned the CO screw to richen the 
> mixture, which would apparently plop the plate up again.  
> Some pics:
> 
> As seen from below (air filter side): 
> http://www.dtwaudi.com/album_pic.php?pic_id=2093
> 
> And from above with mtereing plate removed: 
> http://www.dtwaudi.com/album_pic.php?pic_id=2094
> 
> 
> I highly recommend anyone who has similar sysmptons look 
> at theirs by taking off their igloo, removing the air 
> metering  plate (10mm bolt) and inspecting the "rest" 
> area for wear or wear-thru.  
> 
> Ingo (tired but glad I finally found the problem)

----- Original Message ----- 
From: "spot.ontheroad" <spot.ontheroad at virgin.net>
To: <urq at audifans.com>
Sent: Wednesday, April 05, 2006 1:44 PM
Subject: [urq] Intermittent stumble


> Hello guys. Any ideas what may be causing the following symptom?
>
> Engine at normal operating temperature
> Accellerate hard and it pulls like a train.
> Air fuel gauge suggests rich mixture under accelleration. All is well.

> Lift off the pedal to change up a gear and accellerate and the air 
> fuel gauge shows lean mixture and she stumbles and doesn't want to go.

> Lift off the pedal and take it easy for a few yards and accellerate 
> again and mixture is rich again and she pulls as she should. If I stay

> on the gas and hold it in a gear it remains rich as it should do which

> suggests to me the fuel supply per se is OK (*) It's making full boost

> as normal (according to the tell tale on my test boost gauge) but I am

> not sure if it is doing so after the upshift in the lean patch because

> of course the tell tale has hit max boost from the accelleration in 
> the previous gear. And I can't drive, watch the A/F and reset the 
> boost gauge between changes. A couple of weeks ago I believed it was a

> simple fuel supply problem and changed the filter but it made no 
> difference. The pump is not noisy .
> The pre-filter sediment trap is clean but does have a bubble or two 
> bobbing around when the engine is running but I can't see this should
make 
> any difference.
> I have not found any air leaks on the intake side. The engine stumbles
if 
> the dipstick is removed while idling suggesting no air leaks. Mixture
at 
> idle is bobbing between lean and stoich as I would expect.
>
> The engine is  2168cc WR
> CR = 7.02
> 1bar wg spring and zener diode
>
> I'm sure it's fuel related despite my comments at (*)
>
> Any suggestions gratefully received. Many thanks in advance. Look 
> forward
> to hearing from you.
>
> Keith
>
> '87WR
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