[s-cars] Saga continues: Miss not from bad WGFV - Could it be the MAF?

[Walsh, Edward]

Chad,

Yes I have a boost gauge.

The boost fluctuation is slow, but when the needle does move, it is a quick
movement.  It really looks/feels like the ECU is adding and taking boost.
If I floor it in 5th, the boost will shoot right up to 17PSI or so and then
slowly creep up to 20 and may back down a PSI or 2 on the way there.  If I
keep my foot in it long enough, I may see 20.5.  This behavior is very
different than my 2 previous S cars (both with MTM1+).  With those cars, I
would floor it in 5th and the boost would rocket to 22-23 and slowly back
off as RPMs increased.

One thing I haven't check is the Ground Strap.... Where would that be?

Thanks, Ed

-----Original Message-----
From: CLAG500 at aol.com [mailto:CLAG500 at aol.com]
Sent: Thursday, April 10, 2003 3:16 PM
To: Walsh, Edward; s-car-list at audifans.com
Subject: Re: [s-cars] Saga continues: Miss not from bad WGFV - Could it
be the MAF?


Ed,

  Don't let this thread die. I have had the same problem off and on since I
did my MTM 1+. I think you have done well to rule some things out. The last
time my stumble went away I had cleaned the connectors and tightened the
ground strap. I had also unplugged the MAF and plugged it back in. The
stumble came back and I wasn't able to get it to go away by cleaning the MAF
plug. I would like to try some contact enhancer but have been spending so
much on bearings and the tool to do them that I don't feel like spending $60
for 5ml of Stabilant. It would be great to finally solve this though. Do you
have a boost guage? I know I can see the stumble as a flutter on the needle
way before I can feel it. When it goes away the needle is very steady. It
also seems like it is running very lean when the stumble is occuring. Keep
investigating. Hopefully one of us will figure it out.

Chad Tobin

In a message dated 4/10/2003 1:03:48 PM Eastern Standard Time,
edward.walsh at agedwards.com writes:

> I realize this thread is getting old, but WTF,  I need da boost.  The WGFV
> is OK, so here is where we, err , I stand:
>
> 95 S6 with 83k
>
> - Plug connectors all have 5K ohm resistance
> - Plugs are good
> - ECU is good
> - WGFV is good
> - Coil pack is good
> - Idle is smooth
> - New O2 Sensor
> - Turbo is quiet
> - Waste Gate is not torn, slides smoothly up and down with no play
> - Power is smooth until about 1 bar
> - Miss is subtle, but prevents boost from hitting 22-23 (MTM 1+) in all
but
> gears, boost fluctuates from 17-20.5 in 5th gear
> - Miss is worst when accelerating hard on the Hway, after coasting in
heavy
> vacuum for a while (like slowing for traffic on a 2 lane road,
downshifting
> from 5th to 4th, then overtaking on the left - big stumbles/brown pants)
> - Miss is most apparent when engine is COOL
> - Motor will over boost to 28+ PSI if floored at low RPM (<2,500) in 3/4/5
> gear.  When boost is that high, the motor makes a different, very rapid
> "thumping" noise.  ECU will sometimes bring boost down to safe levels, but
> sometimes it won't, and only my right foot prevents a grenade.
>
> Everything in the ignition system checks out.  Boost plumbing seems fine.
> Could the MAF be throwing bad values to the ECU under high boost? (I use
> paper filters)  Is there a test procedure for the MAF?
> Could a bad MAF
> cause the mentioned symptoms?
>
> Thanks for any/all advice,
>
> Ed


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