85 4kq power hesitation when cold (FAQ)

ben swann benswann at comcast.net
Mon Mar 10 11:24:03 EST 2003

Here we go again...one for FAQ.

After performing the routine maint. - Air Filter change and clean air
sensor plate/fuel distributor assemble and throttle body - while at it,
a good time to check injector pattern (not necessary unless you have
ruled out other things).

Replace/check ign. cap/rotor/plugs.

Check/replace all vacuum lines.

Basically a general, yet thourough cleaning and going over things.  OK -

Now that we have gotten all that out of the way, you can get to the
things that drive you crazy:

O2 sensor - can cause this problem.  I recently disconnected one and
the problem went away, allowing me to adjust so car could be driven
until replacement.  O2 sensor was throwing the mixture off.

My bet would be on: Fuel Injectioon Thermo-sensor located on bottom of
cooling neck.  This has been culprit on every one of these cars I have
seen - at least 5 in the last year at Ben's DIY home of neglected AUDIs.
You can test to see if good, or just buy one from
Rod at thepartsconnection.com and cut to the chase.  They have MTBF of
about 130 kmi in my guestimation.

Differential pressure regulator - if dirty/clogged can cause this
problem, or worse.  Can be removed an cleaned.  If this is a problem,
there may be things in the system before it that are dirty/gummed

..I've also seen a number of bad fuel pumps too - nasty job, but if
your fuel is questionable or history of the car, may want to at least
disconnect the line from pre-filter and see if it is loaded up or not.
Be careful with GAS!

Other stuff - probably, but there is a bunch of stuff I mention above
that should be ruled out first.

Happy Hunting.


[Hello listers,
Unable to locate an answer to this common 4kq problem in the archive so
I look to you for assistance. I have an 85 4kq with 110K, my issue is
when the engine is cold; idles and starts fine, but when I attempt to
take off and drive there is very little power, allot of hesitation,
especially going up hills, but after 5 minutes or so, temp gauge needle
gets to 4 o'clock, the car jumps to full throttle and has good power
after that, like a sticky breather valve not allowing it to breathe. I
can not see or hear any potential vacuum leaks, just changed the temp
sensor to the ecu (a problem you listers helped me with), plugs, wires,
cap rotor, fuel pump/filter, air filter are clean/new.  I have been
dealing with this for the last 5 months (just let the car warm up..),
but I guess I am becoming impatient now and want to try to resolve the
problem.  Thank you in advance for your thoughts..
85 4kq 110K
85 4kq 95K clean parts car]

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