Re: [DML] Part Throttle "bucking"...

["Walter" <Whalt@xxxx>]

Eric,

> upon HEAVY
> acceleration - the problem does not exist.

This evidence should eliminate anything in the fuel tank -- pick-up screen,
suction hose, fuel pump, fuel filter.

> Nor does it exist during
> an idle or during level cruising (as long as you keep the lightest
> touch on the accelerator.

What happens when you don't keep pressure on the accelerator? The engine
runs rough? This makes me think that perhaps the problem is a dragging idle
speed motor. I have a spare in addition to the one on my car if you want to
swap them out and see.

> The problem does NOT exist when the engine is cold, or even cold-warm.

This evidence should eliminate anything to do with the Lambda system.

> But gets worse as the engine comes up to temperature.

This is really unusual, and I have never read of this before in the DML
archives.

> I believe I have it down to a specific area or circuit. I'm now left
> looking at a few components: The Control pressure Regulator, the cold
> start injector, or the (ugh) fuel distributor.

Since the problem is temperature related, it would seem natural to suspect
some part of the engine that is temperature sensitive. The most obvious one
left is the CPR. But usually the problems that I hear about on these are
only while the unit is cold. I suspect that your CPR may be stuck on a low
pressure output which has an inverse effect in the fuel distributor (making
the engine run too rich). It may be rich as it is warming up, but it is
designed to do this per se. But then after your engine is warm, the CPR may
be keeping the pressure too low when it should gradually increase. That is
just a theory.

It may also be that your cold start valve is leaking. This would make the
fuel mixture too rich also, but if it were leaking bad enough then it might
also cause a hot start problem which apparently you don't have.

The way to check both of these theories is with a fuel pressure gauge. What
may make this difficult is that you may need to drive the car in order to
demonstrate the problem. Doing this while having a fuel pressure gauge
temporarily mounted in the engine compartment isn't a very safe thing to do.

I have a fuel pressure gauge you can borrow. If you want to make an
afternoon of it, we can swap parts between our cars to find the problem. I
have a few extra copper crush washers, but not enough to swap out the fuel
distributor. (But that shouldn't be necessary). If you come up with a hand
full of crush washers, I have a spare fuel distributor which I'm curious to
test.

Walt Tampa, FL