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

[CLAG500 at aol.com]

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