[V8] V8 surging problem continues

[Michael Larosa Jr]

my notes about surging.....

Hope they help :)



aukdav wrote:
> Having some teething problems with my recent find.  1990 V8Q  When I picked it up it had moderate surging problem. 
> 
> A read of archives told me 02 sensor was to blame.  Changed the 02 sensor with the tried and true Bosch generic.  No improvement. 
> 
> Checked the #5 fuse, it was fine. 
> 
> Changed the fuel filter, no improvement. 
> 
> Changed the NTS sensor on the back of the left head.  No improvement. 
> 
> WOT gives good smiles. 
> 
> What is the next step? 
> 
> Thanks, 
> Dave 
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-- 

     _/_/_/  _/    _/  _/     _/      Mike LaRosa
    _/      _/    _/  _/_/   _/       TSE - HAS
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      _/  _/    _/  _/   _/_/         Nashua, NH 03063
_/_/_/   _/_/_/   _/     _/
   S U N                              Phone: 781/442-1250
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                                      Email:mc.larosa at sun.com
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Hi Everybody,


Every once in a while I peruse through the archives for V8 stuff.

I noticed all the questions about surging.

It seems you guy's are going down the correct path....

DON'T REPLACE PARTS WITHOUT DUMPING CODES FIRST,
CAN GET VERY EXPENSIVE !!!

Here are my experiences with surging in my 90 V8.

Yes it does the stepped surging in increments of about
200-300rpm at a time.  Still does..... I'll explain later...

Note: First thing I did was to buy the sunpro multimeter that
      it pretty much a pre-requisite if you plan to fix your Audi :-)

Dumpcodes:

Grab a standard automotive single pole 12v light bulb (Like one of the
rear light bulbs or something similar) solder a wire to the side and 
one to the bottom.  Or cobble something together like I did and 
simply wrap the wire around it and tape :-)  Black plastic electrical 
tape is acceptable here :-)

You know have a VAG 1551.... or close enough.. for today's lesson. :-)

Under the passenger side carpet are 4 jacks to stick the wires into

See previous post about making a test wire.....and how to dump codes...



Troubleshooting tips for surging:

Does it surge if you floor it ?  

No, then gas is probably ok.

Yes, I would change gas stations.  Throw in a few applications of techron...

	Use 93 or better octane!!!

Does it surge in the first 20-30 seconds of running when stone cold ?

No,  The car runs in open loop or preset sensor signals for the first 20-30
     seconds.  No ECU involvement as far as automatic ignition timing
     changes and such.
     
     Possible problems:  O2 sensor, Hall Sender, ECU itself.
     
     The O2 sensor you can test with the multimeter from the harness
     on the drivers side, back of head connector.
     
          
Yes, Back to possible bad gas problem...



In my particular instance, I have a bad Hall Sender which required
replacing the complete distributor.  Big Cash for me, decided not 
to do it yet.....  This was verified by the Dump Codes.

Of course when I did get the cash, it didn't make a difference... dddooohhh.

Tech Tip:

One thing I also did here was go to Radio Shack and buy a couple of
adjustable potentiometers in the 5-5000 ohm range.  I then would 
preset them to an ohm level that a sensor should be feeding the 
engine and plug into the wiring harness. Test drive to see if a 
change has been affected.   I checked every sensor related to the
engine to confirm which sensor was hosed.

And yes there are quite a few of us V8 owners who peruse the list
on occasion :-)

Regards,

Mike LaRosa  (978) 442-1250

P.S. Just for fun,  Remove the Air Filter cover and go for a quick
     blast around the block.  Sounds like you could suck squirrels 
     off the street into the intake from 10 feet away :-)