fuel problem (starvation?)
 

Hi all,

I'm trying to solve a fuel / ignition problem in my '87 5000S Quattro.

About 6 months ago I bagan having hesitation problems, hard starting,
weak engine until warmed up (only the first minute or so), and a
smelly exhaust. It's gotten progrssively worse, and now runs with a
high idle as if the mixture is very lean.

I've replaced the oxygen sensor and fuel flter, and last year the fuel
pump went so I doubt its that. I've tested the mass air flow
potentiometer, and the flapper moves freely. When I bought the car
seven years and 250K miles ago I replaced the fuel differential
pressure regulator. Does anyone suppose that this is the problem? Or
does it sound like something else?

Thanks, Jaz

Re: fuel problem (starvation?)
 

On Mon, 8 Sep 2003 20:05:45 -0500, "Stephen Clark" <nospam> wrote:

>Has the cat converter ever been changed? If not, it's time.
>
>Mine was rattling like a can of marbles at 250K.

Nope -- I haven't changed it... just welded up various breaks in the
exhaust over the years. Are there any tell tale signs of Cat failure?

Re: fuel problem (starvation?)
 

1) Sulfur smell or visible emissions from tailpipe.

2) Rattling sound from loose substrate.

3) Failing emissions test with high NOx.

4) General poor starting and running characteristics from incorrect back
pressure.

5) Poor gas mileage.


"Jaz" <harbell@NObeer.com> wrote in message
news:s2kqlv8p9sg0qhu9m02j64m873evk91sb7@4ax.com...
> On Mon, 8 Sep 2003 20:05:45 -0500, "Stephen Clark" <nospam> wrote:
>
> >Has the cat converter ever been changed? If not, it's time.
> >
> >Mine was rattling like a can of marbles at 250K.
>
> Nope -- I haven't changed it... just welded up various breaks in the
> exhaust over the years. Are there any tell tale signs of Cat failure?

Re: fuel problem (starvation?)
 

Another way to check the cat:
The steel tube from the header pipe that has a blue plastic cap on it,
near the intake manifold. Pull the blue cap off and rev the engine.

If the cat is clogged exhaust will come out this tube a lot.

If cat is OK it will create a suction.

Bet the CAT is bad : (

Tony
'91 100Q 5spd

Jaz wrote:
> On Tue, 9 Sep 2003 00:26:58 -0500, "Stephen Clark" <nospam> wrote:
>
>
>>1) Sulfur smell or visible emissions from tailpipe.
>
> Yes, sulfer stink...
>
>
>>2) Rattling sound from loose substrate.
>
> Not as far as I can tell..
>
>
>>3) Failing emissions test with high NOx.
>
> I don't need emissions test for another year, but I bet it would
> fail...
>
>
>>4) General poor starting and running characteristics from incorrect back
>>pressure.
>
> Yep...
>
>
>>5) Poor gas mileage.
>
> Not particulary... it still gets 24 mpg, which seems good for ~300K
> miles (odometer broke six years ago at 150K)
>
> Any idea where I can find a *cheap* exhaust system?
>
> Note that I've been thinking of calling it quits, 'cause I don't want
> to throw lots of $$ at this problem and not get results. However, if I
> were sure that it's the Cat then since it does need an exhaust system,
> then perhaps I can find an inexpensive replacement, say through JC
> Whitney or elsewhere.
>
> Any suggestions?
>
> Thanks again, all
>
>
>>"Jaz" <harbell@NObeer.com> wrote in message
>>news:s2kqlv8p9sg0qhu9m02j64m873evk91sb7@4ax.com. ..
>>
>>>On Mon, 8 Sep 2003 20:05:45 -0500, "Stephen Clark" <nospam> wrote:
>>>
>>>
>>>>Has the cat converter ever been changed? If not, it's time.
>>>>
>>>>Mine was rattling like a can of marbles at 250K.
>>>
>>>Nope -- I haven't changed it... just welded up various breaks in the
>>>exhaust over the years. Are there any tell tale signs of Cat failure?
>>
>

Re: fuel problem (starvation?)
 

Thank you for this suggestion!

I've just tried it, but I see nither suction nor exhaust blowing out
-- just a bit of a vibrating/pulsing wind. When I attach a hose to
this port (now with the engine off) and blow into it, I find
considrable resistance, but no pressure builds (I blew into it with a
lot of force and for as long as I could, but then felt no pressure
pushing back -- as if the tube is a bit clogged at its connection to
the exhaust manifold).

Does this mean anything?
Thanks, Jaz

On Tue, 09 Sep 2003 23:48:34 -0500, TonyJ <tonyjNOSPAM@NOSPAMvisi.com>
wrote:

>Another way to check the cat:
>The steel tube from the header pipe that has a blue plastic cap on it,
>near the intake manifold. Pull the blue cap off and rev the engine.
>
>If the cat is clogged exhaust will come out this tube a lot.
>
>If cat is OK it will create a suction.
>
>Bet the CAT is bad : (
>
>Tony
>'91 100Q 5spd
>
>Jaz wrote:
>> On Tue, 9 Sep 2003 00:26:58 -0500, "Stephen Clark" <nospam> wrote:
>>
>>
>>>1) Sulfur smell or visible emissions from tailpipe.
>>
>> Yes, sulfer stink...
>>
>>
>>>2) Rattling sound from loose substrate.
>>
>> Not as far as I can tell..
>>
>>
>>>3) Failing emissions test with high NOx.
>>
>> I don't need emissions test for another year, but I bet it would
>> fail...
>>
>>
>>>4) General poor starting and running characteristics from incorrect back
>>>pressure.
>>
>> Yep...
>>
>>
>>>5) Poor gas mileage.
>>
>> Not particulary... it still gets 24 mpg, which seems good for ~300K
>> miles (odometer broke six years ago at 150K)
>>
>> Any idea where I can find a *cheap* exhaust system?
>>
>> Note that I've been thinking of calling it quits, 'cause I don't want
>> to throw lots of $$ at this problem and not get results. However, if I
>> were sure that it's the Cat then since it does need an exhaust system,
>> then perhaps I can find an inexpensive replacement, say through JC
>> Whitney or elsewhere.
>>
>> Any suggestions?
>>
>> Thanks again, all
>>
>>
>>>"Jaz" <harbell@NObeer.com> wrote in message
>>>news:s2kqlv8p9sg0qhu9m02j64m873evk91sb7@4ax.com ...
>>>
>>>>On Mon, 8 Sep 2003 20:05:45 -0500, "Stephen Clark" <nospam> wrote:
>>>>
>>>>
>>>>>Has the cat converter ever been changed? If not, it's time.
>>>>>
>>>>>Mine was rattling like a can of marbles at 250K.
>>>>
>>>>Nope -- I haven't changed it... just welded up various breaks in the
>>>>exhaust over the years. Are there any tell tale signs of Cat failure?
>>>
>>

Re: fuel problem (starvation?)
 

Yes, sounds like the tube is clogged. Try feeing a thick wire through it
to open it up.

OTOH, the small sputtering that you found is not too bad. If the link is
clear, the biggest thing to be worried about is a lot of pressure coming
out of it indicating a clogged CAT.

Tony
'91 100Q 5spd

Jaz wrote:

> Thank you for this suggestion!
>
> I've just tried it, but I see nither suction nor exhaust blowing out
> -- just a bit of a vibrating/pulsing wind. When I attach a hose to
> this port (now with the engine off) and blow into it, I find
> considrable resistance, but no pressure builds (I blew into it with a
> lot of force and for as long as I could, but then felt no pressure
> pushing back -- as if the tube is a bit clogged at its connection to
> the exhaust manifold).
>
> Does this mean anything?
> Thanks, Jaz
>
> On Tue, 09 Sep 2003 23:48:34 -0500, TonyJ <tonyjNOSPAM@NOSPAMvisi.com>
> wrote:
>
>
>>Another way to check the cat:
>>The steel tube from the header pipe that has a blue plastic cap on it,
>>near the intake manifold. Pull the blue cap off and rev the engine.
>>
>>If the cat is clogged exhaust will come out this tube a lot.
>>
>>If cat is OK it will create a suction.
>>
>>Bet the CAT is bad : (
>>
>>Tony
>>'91 100Q 5spd
>>
>>Jaz wrote:
>>
>>>On Tue, 9 Sep 2003 00:26:58 -0500, "Stephen Clark" <nospam> wrote:
>>>
>>>
>>>
>>>>1) Sulfur smell or visible emissions from tailpipe.
>>>
>>>Yes, sulfer stink...
>>>
>>>
>>>
>>>>2) Rattling sound from loose substrate.
>>>
>>>Not as far as I can tell..
>>>
>>>
>>>
>>>>3) Failing emissions test with high NOx.
>>>
>>>I don't need emissions test for another year, but I bet it would
>>>fail...
>>>
>>>
>>>
>>>>4) General poor starting and running characteristics from incorrect back
>>>>pressure.
>>>
>>>Yep...
>>>
>>>
>>>
>>>>5) Poor gas mileage.
>>>
>>>Not particulary... it still gets 24 mpg, which seems good for ~300K
>>>miles (odometer broke six years ago at 150K)
>>>
>>>Any idea where I can find a *cheap* exhaust system?
>>>
>>>Note that I've been thinking of calling it quits, 'cause I don't want
>>>to throw lots of $$ at this problem and not get results. However, if I
>>>were sure that it's the Cat then since it does need an exhaust system,
>>>then perhaps I can find an inexpensive replacement, say through JC
>>>Whitney or elsewhere.
>>>
>>>Any suggestions?
>>>
>>>Thanks again, all
>>>
>>>
>>>
>>>>"Jaz" <harbell@NObeer.com> wrote in message
>>>>news:s2kqlv8p9sg0qhu9m02j64m873evk91sb7@4ax.co m...
>>>>
>>>>
>>>>>On Mon, 8 Sep 2003 20:05:45 -0500, "Stephen Clark" <nospam> wrote:
>>>>>
>>>>>
>>>>>
>>>>>>Has the cat converter ever been changed? If not, it's time.
>>>>>>
>>>>>>Mine was rattling like a can of marbles at 250K.
>>>>>
>>>>>Nope -- I haven't changed it... just welded up various breaks in the
>>>>>exhaust over the years. Are there any tell tale signs of Cat failure?
>>>>
>

Re: fuel problem (starvation?)
 

On Tue, 09 Sep 2003 23:48:34 -0500, TonyJ <tonyjNOSPAM@NOSPAMvisi.com>
wrote:

>Another way to check the cat:
>The steel tube from the header pipe that has a blue plastic cap on it,
>near the intake manifold. Pull the blue cap off and rev the engine.
>
>If the cat is clogged exhaust will come out this tube a lot.
>
>If cat is OK it will create a suction.

Hmm, this is not my experience. I've just come back from the muffler
shop, where I had them replace the cat. The tube still blows both at
idle and when the engine is revved. Granted, the sulfer smell is gone,
so perhaps the cat as blocked or not functioning, but it still idles
high and is hard to start.

To recap, about 6-9 months ago the engine began cutting out. When it
happens, if I feather the gas lightly it comes back in 5-10 seconds,
but if I stomp on it it just revs down as if I killed the ignition. As
time went on, the cut-outs have became less frequent, but it also has
become hard to start; sometimes I have to crank it for a long while
before the engine catches, and even then it's one cylinder at a time
(tho the cap and plugs are fine). Just a week ago it started to idle
high (~1200 rpm) and the fuel meter crapped out (the computer reads a
constant 200 mpg and the "distance 'til empty" reads 0.0). The fuel
pump and filter were changed about 24 months ago, and the differential
pressure regulator about six years ago. I'm guessing it has 300K miles
on it (odometer died five years ago, but the trip meter works
sporatically). I've checked all the electical connections (to diff.
pres. reg., cold start injector, and intake manifold pres. sensor),
but I have no wany of knowing is any of these devices are bad.

So, now I've just dumped another $225 on this problem and it's still
not running quite right. What's worse is that the resonators were
toast, and knowing that I wanted to keep it on the cheap they
straight-piped them, so now it sounds like a racy truck (oh joy...
Not).

Any more suggestions?
Thanks, Jaz