hesitation / bog down

[urq]

No MC engines came with a bypass valve from the factory.  I second Steve's
suggestion (was about to post it myself) ... there's a "decel" valve that
bypasses the CIS' airflow metering plate to shut off the fuel on
deceleration, if it stays open too long you get no fuel for your intake air.
An MC that dies when decelerating, say at a stop light can be due to a
sticky ISV as well, but that will not cause a bogging down.

Steve Buchholz

-----Original Message-----
From: quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com] On
Behalf Of Andrew Dickinson
Sent: Friday, December 11, 2009 12:07 PM
To: hayes myers; Brett Dikeman; quattro at audifans.com
Subject: Re: hesitation / bog down

Sounds like a vac leak to me... like Bret said, a BPV is essentially a 
closed loop around the compressor.  leave it open all the time and boost 
bleeds off.  gives a similar problem to AF that leaking vac hoses do.
----- Original Message ----- 
From: "hayes myers" <hayesmyers at gmail.com>
To: "Brett Dikeman" <brett.dikeman at gmail.com>; <quattro at audifans.com>
Sent: Friday, December 11, 2009 2:46 PM
Subject: Re: hesitation / bog down


> Sounds lke i should have a Mityvac. .. I don't think i hae a bypass valve
> but could check. (turns out there was a cut-in on MC2 midstream of 91 
> which
> may make this tricker to figure out.)I did buy a bypass valve (ala Ben
> Swann) but haven't hooked it up yet...could be that it is time. I was
> thinking maybe clogged injectors (had run couple of tanks with injector
> cleaner in the mix)..or perhaps a dying fuel pump.  I'll see if i can't
> follow the checks you indicate below and see what's what.  So begins the
> deeper learning of CIS methinks.
>
> Thanks Brett!
> Hayes
>
> On Fri, Dec 11, 2009 at 2:36 PM, Brett Dikeman 
> <brett.dikeman at gmail.com>wrote:
>
>> On Fri, Dec 11, 2009 at 1:41 PM, hayes myers <hayesmyers at gmail.com> 
>> wrote:
>>
>> >  let off and revs fall off like it's going to die.
>>
>> Classic signs of bypass valve failure, at least on the 20v's; the dead
>> giveaway is when the report is of the engine idle dipping or engine
>> dying coming off a freeway exit ramp.  It's almost always the cause
>> for that exact symptom.  Don't the late 10v MC2s have bypass valves
>> too?
>>
>> If you've got a mityvac, disconnect the control line from the intake
>> manifold and apply vacuum.  The problem can be either the control line
>> cracking, or the valve diaphragm tearing.  It's a $50-ish part, so
>> definitely test before you replace.
>>
>> If the valve is fine (or you don't have one)- maybe check that the
>> metering plate moves smoothly?
>>
>> Oh, also, is the ISV clean and working smoothly?  If it's gummed up,
>> it can stick in a position where it is almost completely closed.
>>
>> Brett
>>
> _______________________________________________
> quattro mailing list
> http://www.audifans.com/mailman/listinfo/quattro
> http://www.audifans.com/kb/List_information 

_______________________________________________
quattro mailing list
http://www.audifans.com/mailman/listinfo/quattro
http://www.audifans.com/kb/List_information