Narrowing down my start issue (84 4kq) [with suggested procedure]

[Ben Swann]

Johnny,

You are slowly but surely ruling things out.  You have ruled out that that problem is
not a leakdown in residual SYSTEM PRESSURE.  That still does not rule out a fuel
pressure problem.  You might want to study the CIS-E operation to get a better idea of
where else to look, as there may be a fuel problem.

If you do things by the book, there are many tests that can be done, and at some point
you may need to go there.  My approach from a DIY/owner perspective is to rule out the
easy and obvious, and some of these things are not by book procedure.

Cody mentions testing fuel pressure and you may need to do this.  It can still be a
residual pressure leakdown, but most likely in the injector side of the CIS system -
that wouild likely be injector(s) leaking down.

Differential pressure is suspect fueling problem now as well, and this can be DPR or EFI
temp sender usually.

Now that you have gotten to the point of things that Cody and Huw, and others are
pointing out, they may want to suggest clever ways to do these tests.  Although I have
done most of these in my ownership of CIS cars, in most cases I never needed to go to
the point of fuel pressure tests  since I usually got things sorted by then.  I do have
the equipement and I know how to do the tests, but they aren't usually easy or necessary
and quite frankly if you are not proficient may be opening a can of worms.

Also, several times I swore up and down that I found all the vacuum leak problems and
resorted to fuel pressure testing only to find out there really was a large glaring leak
I had not found yet.  One of my most haunting was an intake hose that did not leak while
trouble-shooting in the garage, but would open up as the engine moved, especially under
acceleration.  How about that valve cover gasket?

--------------------------------------------------------------

On the engine you have KX/JT with CIS-E, I had around 20 or so of these cars = 4kq and
CGT that were seriously neglected to the point of non-running.   Many of these were hard
starters or had poor drivability cars that owners threw towel in on.  I got a lot of
cars for a few hundred bux and generally got running quite well within a few days.  On
more than one occasion, I'd buy a car that the owner had to get rid of and after
Money/title exchange I'd fix on the spot well enough to drive and the owner would try to
buy it back at 3X what I paid.  I'm mentioning this since some of my methods are not
always "by the book".

With this engine I have evolved a particular methodology that seems to work:

Clean/replace cap and rotor and verify good ignition. Check plugs and note condition.

Fresh fuel and filter is a good idea, especially if the car had been sitting, and if for
a long time, run the fuel into a container and fill with fresh.  

Replace the air filter and in process do thorough fuel meter and plate cleaning.  Check
for smooth operation of plate and metering assembly and that the plate is pefectly
centered and does not bind.  A binding plate will cause the problem you described.

Invariaby I find and fix a great deal of bad air hoses and vacuum lines.  Often the
waffle hose wasn't seated right or has a large crack in it.  There are a lot of hidden
hoses, particularly going to the Evaporative canister.

The throttle body and ISV get a good clean  - remove/inpect the intestinal shaped ISV
hose where there is a small orfice valve that gets blocked.  That hose often collapses
causing ISV not to flow properly.  Check Throttle operation and switch operation - WOT
and idle (verify contacts closing with a meter).

Unless the car is starting and running rock solid, I'll pull injectors and test the
spray pattern.  New O-rings are installed and any marginal injectors are replaced.
Injectors tend to leak down which generally contributes to hard start - more of a hot
start problem, since Cold Start Injector operates when engine is cold.

Usually by this time things are running well, but often adjustments need to be made to
Air/Fuel mix that may have been tampered with to compensate for all the leaks.  Huw has
good info on doing this on his site.

If I suspect a bad sensor or wiring, I'll try to verify it is bad with VOM before
purchase and replace - these things can get expensive.  I have many EFI temp senders
that were replaced just to be sure and I think I have actually found very few of these
out of spec.  Sometimes they seemed to be, but that was more due to testing method or
faulty tester (human/me or equipement/VOM).

If problem happens when engine goes closed loop, O2 sensor is suspect as much as
anything.  A simple test of unplugging the sensor wire after gong closed loop can be
revealing.  I have had my hand on fixing no less than 20 cars that ran like crap or died
a few minutes into warmup and pulled the 02 lead - viola! Runs great - replace sensor
and move on if this happens.

Other things to look for might include bad ground connections at manifold and engine
bell housing to chassis.  Peel back boots of sensors and switches to make sure wires are
still intact.

If after you have done all this relatively easy and straight-forward stuff you probably
then want to look at more in-depth tests such as fuel pressure and delivery.  DPR test
could be crucial since this is the main means of regulating pressure to injectors.  

Although I advocate converting to EFI on many of the older CIS turbo engines, I really
don't think it is a great idea to do it on the 4kq - until you do a turbo swap that is.
On these non-turbo engines, it really doesn't get much more difficult and once you
figure out the culprit, you'll likely find you have one of the easiest to troubleshoot
and maintain engines ever the Audi 5 cyl with CIS-e.

I hope others chime in with their additional suggestions, but please don't bash my
methods as they have served me well.  I'd like to post this in my FAQ, so welcome
additions or improvements. I just don't like to waste time on unecessary procedures.
When need be, I resort to following procedure as evidenced by shelves of Bentley
references with fingerprinted pages in my garage, but they are mostly good for the
wiring diagrams.

HTH

Ben

-----Original Message-----
From: Huw Powell [mailto:audi at humanspeakers.com] 
Sent: Sunday, August 15, 2010 8:18 PM
To: Johnny B
Cc: benswann at verizon.net; quattro at audifans.com
Subject: Re: Re. Narrowing down my start issue (84 4kq)

> Starting to get discouraged... if you give it any throttle over a  light touch of the
gas pedal for the first minute (when cold) it bogs and wants to die. Does the same when
hot but only for the first 8-10  seconds... Im thoroughly stumped. Car has great power
through the RPM  band, top & low end are fine, idle is always rock solid just shy of
1k, cannot source any vac leaks with the chemtool when warm or cold... not really sure
what else to check. Once the start symptoms pass, the car is perfect.. it doesnt drive
like it has any issues at all which just adds to my frustrations. <

So the problem is occurring before it goes into closed loop and uses the OXS to regulate
the mixture.

If someone has tinkered with the static adjustment (the 3mm thing), it may very well be
too lean or rich during this phase, since there is no feedback.

You mentioned picking up the bits to measure the control pressure actuator current.  Get
them, or hack something together and do it.

You mentioned the PO messing with it for "emissions" purposes, who knows where they left
it...
--
Huw Powell