engine won't rev over 2000 RPM (thanks)

Thu Feb 7 04:51:09 EST 2002

Had a similar problem (except my rev limit was 2500).
With the help of the list, I was able to attribute it to
a clogged cat. See if banging the cat makes a noise
or "resets" the problem. That was how I was able to make
sure it was the cat that was giving me problems.
Basically, I drove around the block...when it acted up I
took my hammer out climbed underneath and hit the cat.
When the car was brought back up to speed the problem
wasn't there (until a hard acceleration forced the
broken cat. piece back to clogging the pipe).

Good Luck
--
Blu
'88 80q--178,000mi.
> Hi Bob,
>
> We have already been there. The car has a new idle switch. I also forgot
>   the possibility of the
>
> - cat itself could be plugged.
>
> Bob wrote:
>
> > Try disconnecting your idle switch, if its shorted, this is what you would
> see.
> > Bob
> >
> > Zsolt wrote:
> >
> >
> >>*This message was transferred with a trial version of CommuniGate(tm) Pro*
> >>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.
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>_______________________________________________
> >>>>>>>>Audifans v8 mailing list
> >>>>>>>>Send posts to: mailto:v8 at audifans.com
> >>>>>>>>Manage your list options: http://www.audifans.com/mailman/listinfo/v8
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>_______________________________________________
> >>>>>>>Audifans v8 mailing list
> >>>>>>>Send posts to: mailto:v8 at audifans.com
> >>>>>>>Manage your list options: http://www.audifans.com/mailman/listinfo/v8
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>
> >>>
> >
> >
>
>