Hesitation and Potentiometer

Suffolk GameServer LAN suffolk.associates@verizon.net
Tue, 30 Jul 2002 01:54:52 -0400

BTDT Potentiometer.  I learned from Huw's post here that the values change
when lifting the air plate.
Here's what I do know.
VW 5cyl fuel distrub's in junk yards ~$40 are a match.
Potentiometer: dealer item except the WHOLE fuel distrib is $300 and the
only way to get it I've been told by the DEALER.

With a ohmmeter: the resistance should be ~300 ohms.  If it climbs to higher
numbers or blinks (infinity or open loop) it is no good.  You can test junk
yard one's like this.  I did.  First one was bad I bought the second good

Also just for kicks, the 5 cyl and 4 cyl ponten... worked but I matched
apples to apples on the repair.

Mine plugged at 189K during a trip to FLA ~3000 miles.
I slammed on the brakes to avoid a wreck in SC and It never ran right after.
 Fuel filter was So plugged it looked like a coffee can (full of grinds)
(changed in JAX) after N.O run bucking and running ehhhhh.  Mechanic was
stumped.  I even drove around with his $300 test equipment measuring fuel
pressure around town.  Pressure never changed but the problem was
intermittent until it came on HARD!

Two weeks and 1200 miles later diagnosis:
The potentiometer was plugged by dirt.

This device keeps pressure on both sides (upper and lower)of the fuel
distrib equal.  Therefore the car runs normal.
Plug it and car runs ehhhhhh. hesitates.  Clear up by always comes back to

Your fuel goes thru these:
Tank, Fuel filter under car in 4000Q into the potentiometer then the fuel
- so clean these in order too..............-

So if you want a well running car change the fuel filter every once and a

I drove from NC to MA (three days) bucking and hesitation that I actually
could go no faster than 25MPH in many stretches of road.
The throttle had a sweet spot I had to find to get it to run constant. 25
MPH or 60 MPH.
Move gas pedal and car crapped out.  (remember the fuel pressure equal

My car bucked and backfired so badly that when I got home to Mass the rear
bumper cover was MELTED from the excessive backfiring!
And in NC I could only start it by Starting fluid spray in the rubber intake
boot AFTER the potentiometer ( fuel distributor air flow plate )

Hope this helps,  If I knew then what I researched to know
-Scott in BOSTON
400K 4000Q sitting for one year and just bought cap and rotor for it to run
it again!
turbo candidate

> Plugs, wires, distributor etc have been verified to be in fine shape. WOT
> switch and idle switch have been respectively fixed and verified OK. Does
> my car have a throttle position sensor which could be FUBAR?

Yes, as prev. posted, you have a potentiometer on the side of the fuel
dist that tracks the air plate.

3 terminals, on side is 5 volts, one is ground.  Either measure the
voltage in the middle the key on, very carefully, or disconnect it and
measure the resistance from the middle  pin to on of the others - it is
very low, I think, just a few ohms from pin 1 to 3 total.

You should see a steady, smooth change over the range while lifting the
air plate.