Engine cut-out, spikey idle and other weirdness...

[Stephen Kormilo]

Tyson,

I only know the answer to #3 for sure. Your '98 A4 is not DBW.

Which plastic covers did you remove? If the problem surfaced after 
removing the covers, then you probably loosened a connection somewhere.

To me it sounds like an ignition problem. Connections to Coils, igniter?

Stephen Kormilo
Nanoose Bay, BC

2002 Audi A4 3.0 - Silver
Departed:
1998.5 Audi A4 2.8 - Silver
1985 Mazda Rx7 GSL-SE - Black

email: stephen at kormilo.ca


-----Original Message-----
From: quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com] On
Behalf Of Tigran Varosyan
Sent: Sunday, March 18, 2007 12:55 AM
To: quattro at audifans.com
Subject: Engine cut-out, spikey idle and other weirdness...

Hi Guys,

I bought my 98 A4Q 2.8 30V about a month ago. Today was the first time that
I took the plastic covers off the engine bay. Driving back from my dad's
house the car just suddenly started acting out. Cruising along at 3000 RPM
the engine would just cut out. The dash lights didn't light up or anything
(as they would in an electrical power loss), all electrical gizmos continued
working, etc. It did not feel like losing a single cylinder - it felt more
like hitting the rev limiter - just total ignition cut that jerked the car
pretty noticeably. It would only last for about a second and then everything
would be OK again. It did this a few times until I pulled over at a gas
station and popped the hood.

Idling there for some time the idle suddenly started jumping around - jumped
to about 1500 on its own, then almost died, then jumped again. Then the
engine just cut out and died altogether. I popped off the covers, reseated
the plugs around the intake - a 3-pin, which I assume is the TPS and another
2-pin, which looked like an idle controller.

Then started the car back up and drove on. The problems continued to happen
about once a minute or so, mostly under cruise and light acceleration. It
died again at a light. Then after some time (maybe 10 minutes) the problems
went away completely.

I have noticed that a dirty MAS seems to be a common problem on these cars
and this sounds totally like something that a MAS would cause. If there is
another sensor in the system that can make the ECU cut all ignition, that
might be it too. It feels like a deliberate ignition cut by the ECU, but I
am not sure why...

#1 Where is the MAS?
#2 What should I use to clean it?
#3 Just for curiosity - is this car drive-by-wire (where the ECU opens and
closes the throttle plate based on a sensor attached to the gas pedal) or
does it still have a physical cable connecting the gas pedal to the throttle
plate?

Any other ideas, suggestions are welcome.

Tyson Varosyan
Technical Manager, Uptime Technical Solutions LLC.
tyson at up-times.com
www.up-times.com
206-715-TECH (8324)
UpTime/OnTime/AnyTime