[s-cars] Low boost / Heavy load stumble

[Walsh, Edward]

Seems like there have been a bunch of questions on this subject, so I'll
throw my hat in the ring as well.

My MTM 1+ S6 will miss at times (usually under hard boost/heavy load in
gears 3/4/5). When the engine does this, the ECU will dial back boost and
the car accelerates like a Taurus.... Then all of a sudden, the motor
"clears its throat" and there is a noticeable jolt of power as boost
rebounds.  I does sounds and feel as if the plug connectors are not making
good contact or as if there has water in the spark plug cavity (There is
definitely not a problem with plugs, connectors or water. I had a 92 S4 with
a broken spark plug connector and it would stumble and miss off and on
boost, the S6 will only miss with heavy throttle). Gentle acceleration never
causes any missing. Peak boost in 2nd gear will sometimes spike to 22psi,
but boost at highway speeds in 5th gear undulates a bunch (boost will hit
18, then back to 15, then slowly to 20). The car also surges a lot at lower
boost levels (bypass OK). Overall Power is also off.
Plugs and connectors are new (plugs nice and tight). Car just passed
emissions and (I kid you not) pulled down a Zero PPM in every category. Car
has no codes. I am thinking weak MAF (I use stock paper filter) or Coils or
some other ignition related failure.... Any ideas where I can look/test?
Thank you, Ed





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