[urq] hesitation, bucking on takeoff - not resolved yet!

[Ben Swann]

I have done all of this.  Don't think the air temp sensor comes into play unless under boost.

I agree, it seems electrical at this point.  As if the fuel pump were stalling or ignition cutting out.  These "cuts" are very fast dropouts.  i don't seem to have the problem when cruising or even accelerating at speed.  It happens when I am taking off from a stop and accelerating.  Once the car get some momentum, I don't even notice any hesitation.  Wierd!

The fuel pump is relayed with a hot only 2' from the battery, so i don't think it is losing power.  It is possible that it may be jamming up with something.  I looked, listened and felt earlier, but obesrved nothing suspect.  The pump is nearly new.  Also, I have the pump jumpered on with the key via relay so even ignition primary (overboost cutout) won't stop it.

I need to find out where the positive feed to the ignition is, as that may be the culprit.  I always make sure the connections on things are clean - grounds, coil terminals, etc.  And this car has had a fairly throrough going over already before the problem and now again as I'm troubleshooting.

I have not observed the tach bouncing, but have not made an effort to look for this - I suspect that since this happens so quickly, it will be hard to see, but I plan to watch for this in the AM.

Ben
  ----- Original Message ----- 
  From: DGraber460 at aol.com 
  To: benswann at comcast.net ; urq at audifans.com 
  Cc: quattro at audifans.com 
  Sent: Wednesday, October 19, 2005 9:17 PM
  Subject: Re: [urq] hesitation, bucking on takeoff - not resolved yet!


  This has got be electrical. Even if the fuel is cutting off it has to be an electrical issue shutting it down.
  In my recent encounters (and continuing) with my recently acquired Black Beast, the 3 things that made significant improvements were
  1) Wire brush and renew the ground for ECU at rear of intake manifold
  2) Wire brush and renew the ground connector at the front pole of the coil (and the ground at the coil base.
  3) Wire brush and renew the connector at Air temp sensor
  (I used Caig magic goo on all of these.)

  With these _very mildly_ corroded, my car would not take any boost over ~3800 RPM. It would buck and cutout being almost as you say "undriveable" at those RPM.  

  I don't think any of these will solve your issue except the air temp sensor. If that is not perfect, bad things will happen with Mr. ECU.
  If you have ever gone up with anyone getting air time for an instrument rated pilots license it gives you a great concept of what our ECU's life is like. The ECU is flying absolutely blind, and needs perfect information from every sensor or it will give a totally bogus output.
  Does the tach needle bounce when this is happening? If so, that points to spark issues.
  I never did solve the bi-annual bucking/cut out/die on the road issue of my now murdered URQ. During those episodes the tach would bounce violently as the car bucked and backfired and finally quit altogether. After shutting ignition off and "rebooting" the computer it would run fine for another 6 months or so.

  Good luck and keep us posted.

  Dennis Graber
  Denver