'87 5KCSTQ reluctant to start cold

Huw Powell audi at humanspeakers.com
Thu Jan 8 08:48:04 PST 2015

Hi John,

You might want to define "cold" for us.  I do remember you mentioning a 
75 dF day.  So that would be a "not hot" engine, rather than "it went 
below zero and the car doesn't start well", right?

- Huw

On 1/8/2015 1:17 AM, John Larson wrote:
> I must not have been clear.  It's a bear to start when cold, easy when
> up to temps.  Hot start issues are often related to intake leaks, such
> as around the injectors, or being too lean for some other reason.  If
> you have an IAC that doesn't affect the idle speed when unplugged,
> there's definitely a problem with that system, and there are tests for
> that in the manual.
> John
> On 1/7/2015 8:37 PM, patrick gillen wrote:
>> John:
>> This winter under cooler weather (we don't get cold in western
>> Oregon), my son's '87 5000CST starts right up when cold but will not
>> start easily when hot; it usually needs to cool off but he usually
>> strategically parks it to compression start it. We did that the other
>> day when out an about and it stunk of unburned fuel when it got going
>> yet the tail pipe runs pretty clean. It is hard to suspect vapor lock
>> as it didn't do this all last summer.
>> Another thing I noticed is the idle varies, running a very lumpy
>> minute at 900, then a smoother minute at 1100, repeat. I haven't been
>> able to rule out the A/C compressor cycling changing the idle even
>> though compressor is bad and I think disconnected. The timing mark
>> does change maybe 5 degrees on the changing idle speed but is pretty
>> steady at each position. Unplugging the aux air regulator makes no
>> change in the idle.
>> I too am baffled; are these your symptoms? I can't tell from your
>> descriptions below.
>> My feeling is this somehow includes the turbo controls as it doesn't
>> seem as neck snapping as it did last summer compared to my old non
>> turbo 5000. Don't get me going on how they managed to completely bury
>> that turbo from any possible maintenance and I also need to understand
>> how the whole turbo bypass system works which is at the south end and
>> buried under a bunch of plumbing on top.
>> Pat
>> -----Original Message-----
>> From: John Larson [mailto:viejoloco at comcast.net]
>> Sent: January 07, 2015 5:05 PM
>> To: quattro at audifans.com
>> Subject: '87 5KCSTQ reluctant to start cold
>> While I've been retired and Audiless for a couple of years, I still
>> have a couple of friends with elderly Audis and they rely on me for
>> service help.  In this case, it's a problem I never encountered while
>> I was wrenching.  Hot start, pretty often; cold start, never. Once the
>> car sits and becomes completely cooled off, it takes an extended
>> period of time to get it to start (like 1-3 minutes of fiddling).
>> Giving it even the slightest throttle makes it worse. Once it's up and
>> running, no problem, and it runs really well.  The cold start valve
>> works, although I didn't time it, the control pressure is under 2 BAR
>> in 75+ degree weather today.  System pressure is within specs, too.
>> Before I dive into this, anyone here inclined to give some informed
>> commentary?
>> Thanks for your time.
>> John.
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