[urq] Intermittent stumble

Brandon Rogers brogers at terrix.com
Wed Apr 5 17:18:30 EDT 2006

so is this behavior abnormal for you?  Could it just be the  fuel system is 
trying to "catch up" to the sudden closing/opening of the airplate?

Seems my WX motor behaved like this pretty often - as in consistently 

I know - not much consolation to you....

'84 ur
----- 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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