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

[Ben Swann]

Subject: Re: [urq] hesitation, bucking on takeoff - not resolved yet!
I thought maybe someone on the regular quattro list might have dome ideas on this.


I am still chasing this problem - '83 UrQ bucking/violent hesitation and no power when accelerating in first and second gear/from a standstill.  Since the problem began here is what I have done to no avail:

1.  Checked airfow plate level and adjusted as it appeared a little high - nope.  Then compared the plate movement to others and noticed it seemed to be binding a little, and did not bounce when dropped.  I replaced with another that moved freely.  Still no improvement to my surprise.

2.  Ran fuel pressure tests as I had been suspecting control pressure too high.  Tried 3 different WUR/CPR units and am using the one which most closely matches desired pressure range and operation according to IST doc.  Pressure when cool 65degF is about 23 PSI and warms up within 5 min to 55 PSI where it levels off.  This seems to correspond with the IST range of 1.5 Bar - 4 Bar. The diagram in IST document.however does not map temp and may not be right.  I noticed the pressure range to be somewhat higher than for CIS in NA coupe.  The problem occured in the same way regardless - other regulator range was 22-45 PSI ( WUR from 2.2l NA Coupe) is the one that was in the car when problem began.  The engine had been running fine for awhile with this regulator, and the problem occured due to no equipment changes.

3.  At this point I pulled the injectors.  All seemed to have a marginal or bad spray pattern, so I broke down and replaced them.  I was sure this would be it, since when I tested them, the injectors came on abruptly/sporadically and dribbled. peed sideways or a stright stream.  Yet after installing them - new injectors and seals, the engine bucks as bad as ever.  The spray pattern was much better and looked like it should.  At this point I am getting rather frustrated.

4. Adjusted duty cycle - have been doing this whenever changing something.  Duty cycle can be adjusted to near 50%, but does not always ocillate around 50%.  Duty cycle does range from 5%-95% under varying conditions, or if I enrich or enlean by adjustment.  Still I decided to swap out the ECU.  Still no improvement.

This problem occurs when the car is warmed up, mostly after having driven, shutdown and restarted, but will happen when driven then hitting traffic.  Car just bucks like crazy when put in gear and given throttle.  Once the car get going, it drives fine, but in lower gears just does not want to go without major hesitation.

5.  Other things replaced in last 6 months/6000 miles:
Distributor Cap, rotor,  spark plugs and wires, new coil(done after problem began). O2 sensor new.  All grounds are clean and good connections to battery.  I continually check for leaks and most of the vacuum lines have been replaced.

6. Fuel pump and filters were new about 2 years ago when I brought the car back from the dead.  Recently changed pre filter and continue to not some accumulation of residue getting caught by pre-filter.  Pressure is good and if anything on the high side - pegs my fuel gauge which stops at 60.  Id guess system pressure is around 90 - using NG pump.  Did not test flow, but nothing to indicate there is a fuel delivey problem - perhaps I need to double check.  Does not make sense that the car seems to have full power at speed, yet not enough to get out of it own way when starting from a standstill.

So presently I'm at a loss as to what is going on - everything I check or change seems to make no difference.

Ben
----- Original Message ----- 
  From: DGraber460 at aol.com 
  To: benswann at comcast.net ; urq at audifans.com 
  Sent: Saturday, September 24, 2005 8:47 PM
  Subject: Re: [urq] hesitation, bucking on takeoff


  In a message dated 9/23/2005 8:05:25 P.M. Mountain Daylight Time, benswann at comcast.net writes:
    This problem has gotten progressively worse on my '83.  Earlier this summer she was running great with no problems except the occasional hard start. Now, particualarly after warm and mostly after shutting down and starting 
    after 15 min. or so, the car bucks and hesitates like crazy on takoff, mostly in first gear, if I double clutch it enough to get some momentum going and shift into a higher gear it'll pull fine and then seems fine at higher speed or cruising.  It has gotten really annoying as often won't get out of its own way when taking off at a stoplight.

    I know it is not the fuel pump cutting out.  O2 sensor has been replaced and attempt at adjusting the mixture make no difference.  The ignition components are new, incl. coil.

    I suspect control pressure, as this happens after it is good and warm. Sometime is hard to start and stalls out after starting fine and then want stay running without giving the particular magic footwork to the throttle. 
    I had recently cleaned airflow sensor and filter, and all was right and it ran good until it started doing this.

    Really strange as it seems to have full power once going over about 7 MPH but off the line bucks like crazy.

    Any ideas or BTDT.

    Thanks,

    Ben