[urq] Running problems caused by "leaning out" 83 urq.

Buchholz, Steven Steven.Buchholz at kla-tencor.com
Tue Aug 29 20:46:30 EDT 2006

The CPR (WUR) pressure specs are documented in the IST Maintenance &
Adjustments doc ... probably the Bentley as well.  I read that with the
engine warm and hoses connected the control pressure should be 3.4 to
3.8 bar ... so I doubt being 0.1 bar over spec will cause a problem.
1.0bar when cold seems to be a bit low, but not too different than 1.25
bar as shown on the chart.  

What do you see the duty cycle do as the engine warms?  Does it show the
ECU trying to richen the mixture (duty cycle increasing)?

Are you sure that you have the correct fuel distributor for the car?

It would be helpful for you to better describe a few things ... based on
your description the car should idle just fine as the engine warms, it
just sputters and such under throttle ... correct?  I'd also like to
know how you prove that the "ECM checks out" ... are you meaning that
the duty cycle operates as described in the IST?  Have you tried
tripping the WOT switch while the engine is sputtering?  How about the
Idle and WOT switches at this time?  

Is the system pressure between 5.2 and 6 bar per the IST?

Steve B
San Jose, CA (USA)
> The regulated fuel pressure is 1 bar cold and 3.9 bars when hot; when
> the car passes 2.00 bars we get lean out and the car will not run
> without stumbling and spluttering. Mixture is too lean. By
> the electrical regulator of the warm up plug, we can extend the
> time of the engine before the regulated pressure is too high for the
> engine to run properly. The heat of the engine then comes into play,
> the ambient temperature will cause the regulator to warm up.
> We know that this is not an O2 sensor problem, as the car reached
> running temperature, the ECM is checks out; fuel pressures are OK,
> injectors are new, the sensor plate in the distributor rises and falls
> correctly.
> Has anyone any idea why the we would get lean out when we pass 2.00
> of pressure? The car will run fine during the warm up phase of say 2
> minutes with the connection made to the warm up plug, or 20 minutes
> it unplugged.

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