4kq acceleration issue

[SJ]

Adding to Ben's list of probable causes.

Lean mix:
Fuel Injector seals
Testing: bendable copper tubing attached to hose which is attached to
propane tank.
With engine idling, move the copper tube in and around all vacuum leak
sources, including in and around the injectors. When you hit the leak, the
idle will change.
Injector seals are rubber O-rings. These can and do dry out, become brittle
over time and result in leaks . .sometimes only under cold/hot conditions.
OK when hot, leak when cold.

Another method of detecting the leak is to watch the O2 sensor voltage.
Disconnect the oxygen sensor from the harness. The engine is now running on
mechanical fuel mixture inputs only.
Also disconnect the DFP connector so the computer cannot correct the
mixture.
Use a sensitive DVM on the disconnected oxygen sensor lead.
Use propane as outlined above to do the leak testing. When you hit a leak,
the O2 sensor reading will change along with a change in idle speed.

High Idle, intermittant:
Sticking throttle body plates. This area gets gummed up over time, and the
plates will stick. If its warm, plates will close. If its cold, the gummy
sludge wont be soft enough to give and the plates wont close.
Remove throttle body and clean thoroughly. Put in new gasket when replacing.

O2 Sensor test:
With engine warmed up:
Pull back insulator from O2 sensor connector.
Attach DVM
Voltage will be swinging back and forth centered around 0.7 volts if the
sensor is OK.


SJ
85 Dodge PU, D-250, 318, auto
85 Audi 4k - - sold but still on the road
88 Audi 5kq
90 Audi 100q


> From: "Ben Swann" <benswann at comcast.net>
> Subject: 4kq acceleration issue
> To: <armodis.list at gmail.com>
> Cc: quattro at audifans.com, 'Ben Swann' <benswann at comcast.net>
> Message-ID: <079401c74f79$4f6e8a30$7001a8c0 at swansong>
> Content-Type: text/plain; charset="us-ascii"
>
> Here are things to do and try - seems the car needs some sorting due to
> neglect.  Once you get it sorted, it will be sweet.
> - The valve cover leaks and the lifters clack pretty bad.
>
> *** Well - seems like you need to replace valve cover gasket.  If you
replace
> lifters then do the gasket at that time.  Lifters are source of clacking.
> Running higher/extended viscosity range ie. 20W50 may help - I like
Castrol
> GTX or even better Syntec 5W50.  Fix your leak before spending the money
for
> Syntec.  Try tightening the cover nuts uniformely to see if it helps with
the
> leak - don't overtighten.  Try running good quality oil before getting
into
> lifter replacement - these engines like higher viscosity oil again
non-synth
> 20W50 (or 10W40 if in cold climate) or 5W50 synthetic and you can run it
year
> round.
>
>
>
> - It idles high, usually a little above 1000.
>
> *** Couple probable causes include: vacuum leaks; Idle stabilizer valve or
> circuit - likely culprit is the idle switch - check/repair/replace - they
all
> go bad over time;  Replace vacuum lines.  You'll likely find some obvious
> culprits.  A lot of folks immediately assume ISV is bad - more likely it
is
> the idle switch and/or throttle body screw o-ring.  Try jumpering the idle
> switch connector and see if the idle drops.
>
> - It has some trouble starting in the cold.  The colder it is, the harder
it
> is to start.
>
> *** As above - vacuum leaks likely culprit.  Also Injector seals.  Might
be
> Fuel Injection Thermo Sender, but do the other repairs first.
>
> - I have to give it some gas to get it to idle steady but then its good to
go.
>
> *** As above - air leaks.
>
> - Sometimes it will almost stall until I get the car moving and then it's
ok.
>
> *** Air leaks!
>
> - The temperature gauge usually sits between the 1/2 to 3/4 mark unless I
have
> the heater on and then it drops down to between 1/4 and 1/2.
>
> *** Normal
>
> -        The motor diesels.
>
> *** Running too lean - air leaks.  Possible other cause, but fix most
probable
> causes first.
>
> *** You need to spend a good day sorting it out.  Be equipped with about
10'
> of good quality vaccum line and some rubber hose bandage tape to repair
any
> OEM hoses that may not be readily available.  Replace the Air Filter and
clean
> out all the garbage.  Clean up the throttle plate area too while you are
at
> it.
>
> Ben
>
> http://www.GTQuattro.com



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