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

[Thatcher Hubbard]

I would suggest that since all of the work you've done to your fuel system
seems to have made little difference that you should check the ignition. You
mentioned that you replaced your coil, have you checked the ignition control
unit?

On 10/19/05, Pasqualoni, James E <james.pasqualoni at gs.com> wrote:
>
> On Wednesday, October 19, 2005 12:53 PM, Ben Swanndered:
>
> 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
>
> ----------------------------------------------
>
> Ben,
>
> Have you tested the throttle position sensor and WOT switch? Try
> unplugging
> it and running closed loop for a while to see if this makes a difference?
> Strange symptoms...
>
> HTH,
> Jim
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