Re: quattro-digest V3 #753

[Alex Kowalski <akowalsk@shrike.depaul.edu>]

Robert Riley wrote:
> 
> >The car began running poorly about a week ago, missing, poor starting,
> >stalling at idle, etc.
> Check your fuel pressure using a guage.  You MAY have a failing fuel pump.
> The pumps in my cars have usually gone out at about 100k but I had one
> that went earlier.  It was very frustrating due to the fact that sometime
> the car would run fine, and then just stop dead at the most inconvienient
> places (middle of intersection, rail road crossing, etc.)
> At other times it would just sputter along with poor acceleration and
> lousy idle.  This caused some fualt codes to be registered, but they were
> not true indicators of the problem.  For example the code said O2 sensor,
> but this was just caused by the ECU trying to keep the motor running.
> Good luck!


Yeah.  I have to say it sounds like a fuel pressure problem to me also.  
Who knows what's causing it:  Fuel pump is a possibility, as well as a 
bad check valve on the FP.  Bad fuel-pressure accumulator, a bad  spring 
inside the fuel distributor, perhaps.  Maybe even the fuel distributor 
proper (i.e., differential pressure regulator or some other, 
non-electronically regulated system within) system is bad. I was informed 
by my mechanic that even if the differential pressure regulator was not 
working properly, the car should run, albeit roughly.  Have the system 
pressure-checked while the engine runs through its cycle from cold to 
hot.  If the pressure doesn't fall in normal range at all times, 
something is not working properly.  Maybe this is the fuel pump.  Also, I 
liked the suggestion to check for sediment in the tank.  I don't know if 
your car is like mine, but the '84 4KQ has a small plastic fuel filter 
upstream of the fuel pump but downstream of the gas tank. Mine got 
clogged by sediment and prevented fuel from getting to the pump in the 
first place.  Maybe this is the problem.  If your car is getting spark 
and air, it's not getting fuel in the right quantity and 
pressure. Please describe more.  Sitting in neutral, can you get the 
engine to rev with <very slight> throttle openings, as this doesn't 
require much extra fuel, but if you press harder you get a stumble?  If 
this is so, you can almost guarantee this is a fuel problem.

Before everything else, check the ignition coil as per the instructions 
in the Haynes manual for your car.  It lists the proper resistance values 
to determine if the coil is OK.  It might be shot. You should be able to 
find one inexpensively.  

Best Wishes,

Alex Kowalski

'84 4KQ