90Q problems

[Huw Powell]

Hey Ron, hope you don;t mind, I am cross posting my reply to you tot he
audifans list... you may get some other/better tips from other people if
I do this!

> Ron Pellerin wrote:
>
> Hi Huw,
>     I have been reading and enjoying your website for some time. I was
> wondering if you could shed some light upon a few quirky things I have
> been observing with my newly aquired 1988 90 Q.
>     Other than spend money on her, I haven't really done a heck of a
> lot to my Quat since she adopted me and my wallet a month and a half
> ago.
>     The previous owner did the timing belt and I have replaced the
> struts with Boge's, replaced the front park lenses with clear ones,
> (one was broken, so, what the heck). I replaced the battery, trunk
> shocks, radiator, rear calipers and e-cables, fuel filter, anti-freeze
> (non-corrosive, of course) thermostat. I have purchased the Euro
> 65/100W lamps and harness. I also have purchased a wire set, cap,
> rotor and Platinums.
>     I will be having the drivers seat leather repaired, and the will
> be painting her in the late winter or early spring.
>     Now, the quirks. When I purchased the car, I do not remember any
> of these problems...Briefly, I will list them.
>
> 1. When accelerating, it seems that there is a "dead" area...around
> 3500-4000 rpm. The car "holds back" it feels like similar problems I
> have felt with worn cams, or tight valves or ..if wound tighter..like
> valve float. If I punch it to the W.O.T. It seems to wake up...Since
> WOT enrichens the mixture I thoght perhaps it's leaning out.

My 90Q has a bit of that too.  I find that unless I am matting it,
sometimes there is a small hesitation around 4000 rpms.  in other words,
it does not like part throttle there.  Now this should not be, of
course...  One theory i have is that since I do get some knock sensor
activity, running premium, my pistons &/or valves probably have some
build up of crud, making detonation more possible than it should be.

at 4k rpms, it could be that in closed loop things are just a little shy
of "running right," it knocks a tad and pulls back the timing.  at WOT
it is running richer and in open loop and so does not do this.  I plan
on trying to clean my pistons sometime to see what that does.

>
> 2. When not fully warmed up the above occurs at even lower rpm and is
> much worse.

I have noticed this but not much.  The real problem is hard accelerating
on a dead cold engine, at the first shift its hard to catch the engine
right and make power - in other words, it pulled fine at 3k - 3500 in
first, but when I try to catch it there after shifting into second, it
is unhappy and bogs a bit.  See above theory, perhaps, and the chances
of small vacuum leaks that have be "tuned to" making the engine mix
wrong when cold for part of the rpm band at certain air volumes.

>
> 3. When fully warmed up the cars idle hunts between 900 and 1200 rpms
> at two second intervals. ( I changed the idle stabilization valve,
> which had no effect, but if I connect a hose between where it was the
> idle goes to 750.

might be grounds at the IM, air leaks at ISV attachment, or... who
knows?

>
> 4. The temperature gauge will only work around the time the engine is
> fully warmed up and the fan cuts in.

it runs off the MFS on the rad hose neck - check there and the wiring.
The MFS's go bad very easily, their connectors get all crudded up, too.

>
> 5. At highway speeds in 5th gear the check engine comes on, and will
> go of if I take my foot of the gas and blip it.
> The emissions passed for Massachusetts, but I have been thinking O2
> sensor.

That one I don't have.  never got a check engine light, yet at least.
Maybe you should check the engine?  Is it still there?

I don't even know what the check engine light is supposed to mean...
ideas anyone?

> If you have any ideas, please let me know. So far, Thermo
> multi-switch, vacuum hoses and O2 sensor are top on my list. Is ther a
> throttle position sensor/potentiometer on this car?

There is a potentiometer on the side of the airbox, and those can be
bad.  They can also be measured to see if the tracks are smooth and
conducting properly.  Nate and I were thinking of playing with these
this spring, since an old 4kq we checked out was actually quite bad.

Good luck finding out what is wrong, and please report back.

Oh yeah, subscribe to this mailing list as well for massive support!

--
Huw Powell

http://www.humanspeakers.com/audi/

http://www.humanthoughts.org/