engine won't rev over 2000 RPM (thanks)

[Zsolt]

Hi Martin,

It is no coincidence. It makes it up to 2000 load or no load, but
sometimes even before it gets there it starts bucking. I can set the
cruise at 2000 though and sail quite smoothly with only occasional
jerking. If I step on the gas however, it looses all power, it does not
stall, but it kills all power. Weird!

So far I was told it could be

- oxygen sensor
- mass air flow sensor (MAF)
- fuel filter/plugged fuel line
- fuel pump
- wiring connections
- speed sending unit/missing teeth on flywheel

Zsolt

Martin Pajak wrote:

> Don't know, coincidence?
> If the speed sensor was faulty most likely the engine would not even start.
> If it fails at high rpm possibly wiring or mounting.  However does it
> consistently fail at 2000 rpm?
> Does not make much sense, than again it's an Audi ;o)
>
> Hope this helps.
>
> Cheers
> Martin
>
>
>>-----Original Message-----
>>From: Zsolt [mailto:zed123 at telusplanet.net]
>>Sent: February 5, 2002 10:47 PM
>>To: Martin Pajak
>>Subject: Re: engine won't rev over 2000 RPM (thanks)
>>
>>
>>Thanks Martin. That's an interesting one. But why would it cause to give
>>  me a speed sensor error?
>>
>>Zsolt
>>
>>Martin Pajak wrote:
>>
>>
>>>Try your catalytic.
>>>If it's pluged it would prevent the engine from reving up.
>>>I used to work at a place that had a Ford Ranger in.
>>>The thing would not rev past 2500rpm.
>>>Any attempt would see it rev-limited.
>>>After half an hour of floorin' someone smeled burning.
>>>It was the exhaust before the cat, cherry red hot.
>>>Very impressive.
>>>
>>>Onece a cat goes, it cloggs pretty quickly.
>>>
>>>Cheers
>>>Martin Pajak
>>>
>>>http://www.quattro.ca
>>>
>>>1983 Audi Ur-quattro (265,000 km) Winter car
>>>1985 Audi Ur-quattro (141,000 km) Euro spec. import ;o)
>>>1986 Audi 4000 S Quattro (442,000 km) with 5 bolt pattern RIP
>>>
>>>
>>>
>>>
>>>>-----Original Message-----
>>>>From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com]On
>>>>Behalf Of Zsolt
>>>>Sent: February 5, 2002 9:47 PM
>>>>To: quattro at audifans.com
>>>>Cc: V8
>>>>Subject: engine won't rev over 2000 RPM (thanks)
>>>>
>>>>
>>>>Thanks for all your responses.
>>>>
>>>>We haven't done anything yet, I wanted to see the responses first in
>>>>case somebody had to deal with a similar problem. I hope we can sort it
>>>>out soon.
>>>>
>>>>Zsolt
>>>>
>>>>
>>>>
>>>>dsaad at icehouse.net wrote:
>>>>
>>>>
>>>>
>>>>>This is a problem no matter what kind of car you have. I
>>>>>
>>>>>
>>>>scrounge up connectors
>>>>
>>>>
>>>>>of all sizes at the junk yard. For the 2 and 3 wire varieties
>>>>>
>>>>>
>>>>you have some
>>>>
>>>>
>>>>>choices. For the bigger stuff like the MAF I would suggest
>>>>>
>>>>>
>>>>making individual
>>>>
>>>>
>>>>>jumper wires using the contacts from old connectors. You end up
>>>>>
>>>>>
>>>>with a sort of
>>>>
>>>>
>>>>>universal breakout box. Fortunately most of the Audi/VW
>>>>>
>>>>>
>>>>contacts are the same.
>>>>
>>>>
>>>>>Only the number and housing shape change.
>>>>>If you can access the back of the connector (on the MAF this is
>>>>>
>>>>>
>>>>possible) you
>>>>
>>>>
>>>>>can just pull back the boot and probe the backside of the
>>>>>
>>>>>
>>>>contacts directly.
>>>>
>>>>
>>>>>You really have to be careful whenever playing with connectors
>>>>>
>>>>>
>>>>to not damage
>>>>
>>>>
>>>>>the contacts with your meter probe or whatever. This is a well
>>>>>
>>>>>
>>>>known and common
>>>>
>>>>
>>>>>cause of future problems.
>>>>>For hard to reach connectors I often can just use a length of
>>>>>
>>>>>
>>>>wire stuffed into
>>>>
>>>>
>>>>>the interesting contact cavity and taped onto the wire harness.
>>>>>
>>>>>
>>>>It aint pretty
>>>>
>>>>
>>>>>or fast  but it is effective and cheap.
>>>>>btw, the manual gives a fair amount of detail for checking the MAF. I
>>>>>discovered that it is also electrically quite similar to other
>>>>>
>>Bosch MAF
>>
>>>>>sensors so any testing methods for them would probably apply.
>>>>>There are pinout differences though.
>>>>>When I wanted to check mine out, I made a test harness from a
>>>>>
>>>>>
>>>>junk connector,
>>>>
>>>>
>>>>>and had another Bosch MAF (actually from a Mazda!) and just
>>>>>
>>>>>
>>>>compared readings
>>>>
>>>>
>>>>>while blasting them with my shop-vac. They both responded the
>>>>>
>>>>>
>>>>same way so I
>>>>
>>>>
>>>>>concluded mine was OK.
>>>>>
>>>>>The timing senders are just inductors (coil of wire) so off the
>>>>>
>>>>>
>>>>car a good test
>>>>
>>>>
>>>>>would be to measure resistance while heating it up with a hot
>>>>>
>>>>>
>>>>air gun. If it
>>>>
>>>>
>>>>>opens up it is bad. On the car try an AC measurement across the
>>>>>
>>>>>
>>>>terminals. The
>>>>
>>>>
>>>>>voltage should vary with speed. If you have an o-scope you
>>>>>
>>>>>
>>>>should see a sort of
>>>>
>>>>
>>>>>sine wave that changes frequency and amplitude with speed.
>>>>>btw, the anti-lock senders work the same way.
>>>>>
>>>>>Dave
>>>>>
>>>>>
>>>>>Quoting "Buchholz, Steven" <Steven.Buchholz at kla-tencor.com>:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>... seems to me this is easier said than done!  It so happens I was
>>>>>>looking
>>>>>>at the same signals on my urq yesterday ... I want to build a
>>>>>>"stimulator"
>>>>>>so I can test the MAC-xx boxes off line.  What I ended up doing was to
>>>>>>open
>>>>>>up the ECU and probe the signals inside it to see what they
>>>>>>
>>looked like.
>>
>>>>>>This is not the sort of thing I'd recommend that the normal
>>>>>>
>>"shade tree"
>>
>>>>>>V8
>>>>>>mechanic try ...
>>>>>>
>>>>>>BTW, I do plan to test the sensors I pulled from my V8 *somehow* ...
>>>>>>actually I'm contemplating comparing the sensor iteslf to the part on
>>>>>>the
>>>>>>ury, and may well simply install one of the sensors from my
>>>>>>
>>V8 onto the
>>
>>>>>>urq
>>>>>>and scope the signal out to see what characteristic failed.
>>>>>>
>>Given these
>>
>>>>>>things are not cheap I may see if there is some way that I
>>>>>>
>>might be able
>>
>>>>>>to
>>>>>>make something that would allow an otherwise "bad" sensor to
>>>>>>
>>be made to
>>
>>>>>>work
>>>>>>again ...
>>>>>>
>>>>>>Steve Buchholz
>>>>>>San Jose, CA (USA)
>>>>>>
>>>>>>
>>>>>>
>>>>>>>Look at the timing and reference sender signals with an
>>>>>>>oscilloscope. If there is a problem you should see it this way.
>>>>>>>
>>>>>>>
>>>>>>>
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>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>_______________________________________________
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>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>>
>
>