Strange cold start on 84 4000 quattro

[Huw Powell]

This definitely sounds like a lack of enrichment when cold, leading me 
to suggest testing that NTC sender, measure resistance in ice water and 
boiling (careful!) water.

I'm surprised that 2200 rpm cutoff doesn't slowly rise as it warms up, 
though.  It's a bit too high to be a stuck idle (closed throttle) 
switch, that makes a brick wall around 1400 rpm.

Someone suggested a vacuum leak, which although I don't think it is, it 
can't hurt to carefully go over all your hoses and fittings.

On 8/8/2010 2:14 PM, DK wrote:
> I had something similar happening to my 86. The coolant temp sensor
> (for the ECU) developed a leak and coolant accumulated slowly at the
> connector. Made the readings go haywire. Disconnect it next time it
> happens to start troubleshooting. I tightened the sensor mine up and
> cleaned the connectors and the problems where gone. My car usually
> took around a minute till it acted normal and would fall flat on its
> face when you tried to drive it.

-----

> The car turns over but doesnt fire. After letting it sit for a few
> seconds, it turns over and coughs, but misses. More turning over and
> then finally it fires and coughs to life. Very choppy but after a few
> blips on the throttle it smooths out to a nice idle just above 1k rpm. I notice here when I blipped the
> throttle a few times it sounded like the motor was bogging, and the intake was quite
>  loud.
>
>
>
> I bring the RPM's up to 2k and its smooth, but at 2200 RPM it bogs
> itself down and brings the RPM back to 2k. If I hold lightly on the
> throttle bringing the RPM up it will cycle this (up to 2200, bog, back
> down to 2k, up to 2200, bog, down to 2k etc etc). If you floor it, it
> just bogs harder. After letting it idle (which during all of this it's
> idling very smooth) 30-45 seconds, all symptoms go away. Runs smooth, rev's
>  up as it should, all problems go away. There was no smoke at start up..
>  I'm definitely stumped.....


-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/