1988 Audi 90 - Air-Fuel Mixture Problem

[Ed Kellock]

My first thought was OXS because of the at least partial relationship
to engine operating temp.

An 88 90 has the NG engine I believe, as does my 87 CGT.  It has a
multi-function temp sensor, but I doubt that is at the root of your
problems.

Ed

----- Original Message ----- 
From: "Ben Swann" <benswann at comcast.net>
To: <schief53562 at peoplepc.com>
Cc: <quattro at audifans.com>
Sent: Wednesday, October 05, 2005 9:12 AM
Subject: 1988 Audi 90 - Air-Fuel Mixture Problem


> Clarification to Kents suggestions below:
>
> 1) Suspect this as the culprit
>
> 2) ISV not likely to cause a accel. hesitation problem.
>
> 3)  No MTFS - there is a dedicated Fuel Injection Thermo Sender
which may be
> dual function for the temp guage as well.  this can definately be a
problem,
> but usually would effect startup.
>
> Again, good to know how to pull codes, but not as easy to do on this
engine
> and not likely to reveal useful information in this case.
>
> I'm assuming here as with other similar posts that the basics have
been
> covered prior to getting to this point.  That includes cap, rotor,
plugs all
> good and air filter changed as air flow sensor checked to be
operating
> freely and cleaned.  Don't assume your Jiffy-Tune boys did any of
this.
>
> Don't even think of messing with DPR until you have ruled other
things out.
> If you think that may be it there is a way to remove and clean it.
>
> Ben
>
> [Date: Wed, 05 Oct 2005 09:10:12 -0400
> From: Kent McLean <kentmclean at mindspring.com>
> Subject: Re: 1988 Audi 90 - Air-Fuel Mixture Problem
> To: schief53562 at peoplepc.com
> Cc: quattro at audifans.com
> Message-ID: <4343D0B4.6000804 at mindspring.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> schief53562 at peoplepc.com wrote:
>  > Our 1988 Audi 90 is a 5 cylinder 5-speed with 198,000 miles.
> ...
>  > So . . . the last recommendation is to replace the fuel pressure
>  > regulator.  I declined for now because they wanted $500 for the
part.
>
> Before you throw more money at the problem (at people who
> seem to be just guessing at the cause), I'd try pulling
> diagnostic codes:
>
> http://www.sjmautotechnik.com/trouble_shooting/10naecu.htm
>
> At the risk of repeating myself, without the codes, I'd also
> check 3 things:
>
> 1) The O2 sensor. When was it last replaced?
> 2) The ISV. It may just need a good cleaning.
> 3) The MFTS (multi-function temp. sensor, if the 90 has one;
>     I'm assuming it does) is also problematic - a frequent
>     source of failure that causes funky problems.
>
> A Google search of the Audifans website will tell you more about
> each of these.  The ISV is also covered in the KnowledgeBase.
>
> --
> Kent McLean
> '94 100 S Avant, "Moody"
> '89 200 TQ, "Bad Puppy" up in smoke]
>
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