BAD stumble/hesitation

[Jason Puckett]

Speaking of fuel pressure problems...
  ok, so I've had this hesitation problem for a while in my '93.  Had to replace several things to get the old girl to pass emissions.  After replacing EGR/BPT it got somewhat better.  After having the dealer do a decarbon service, throttle body cleaning and me re-installing the stock intake the hesitation got MUCH worse.
   
  There are two scenarios when it appears.
  1.   Driving on the freeway - cruising at 70ish in 5th 3300 rpm - almost exactly every minute it starts to stumble, like the car is coughing....cough, cough, cough...for about 3-4 seconds, then it stops.  1 minute later...cough, cough, cough...stops...  No noise when it does this, just cuts in and out.  It will do this regularly all the way home.  Doesn't matter if the A/C is on or off.
   
  2.   Under pretty heavy acceleration...usually in 4th gear - like when entering the freeway - around 4K rpm with about 85% throttle it feels suddenly like I"ve hit a brick wall - BAD stumble...like the car is choking.  It will stop if I give it full throttle for a few seconds.
  I can re-create the situation by downshifting from 5th to 4th and giving it more throttle, I'll accelerate up till I hit the 4K rpm mark, then it stumbles again.  If I just keep the throttle at the same spot around 85% in 4th the car will actually begin to lose speed, it accelerates up to that then starts slowing down even though the rpms still read 4K.
   
  I am thinking it may be a fuel pressure problem or maybe ignition problem?  Could this be the MAF ground problem?
   
  What's so wierd is how predictable it is.  When it does the stumble while cruising you can almost set your watch by it, its so regular.
   
  HELP!
   
  Thanks
  Jason Puckett
  '93 Ruby Pearl SE-R
  '91 Super White Maxima
   

       
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