bucking when hot

urq urq at pacbell.net
Thu Jan 19 02:13:36 EST 2006

... you don't have to go to the trouble of hooking up the MIL ... and all 
you need to access is the fuel pump relay.  The light bulb goes from one 
terminal to ground, and you activate the diagnostic mode by shorting the two 
pins on the FPR.  If you happen to have an MIL, all you need to do is to 
plug a fuse into the FPR!

You really should let the codes give some clues before getting too carried 
away with swapping parts IMO.  I had a "bucking problem" on my '88 5kCSQA 
which turned out to be caused by a massive intake leak that was due to 
deterioration of the crankcase vent hose that attaches to the fitting on the 
crankcase below the spark plugs on the side of the engine.  This one wasn't 
heat dependent, but it was dependent on load because when the engine was at 
WOT it rocked ever so slightly in the engine bay and opened up a hole.  One 
possibility that may be more related to temperature might be the engine 
reference or speed sensors ... or the Hall Sender on the dizzy for that 
matter.  Look at the tach when the engine bucks ... do you see the tach 
abruptly drop when the engine is misbehaving?  If so, it indicates that the 
sensors the ECU needs to determine when to make a spark are malfunctioning 

Steve B
San Jose, CA (USA)
> I would like install the check engine light to read any codes but am not
> sure where to access terminal 31, and 33 on the ECU for it to blink out
> codes. Scott Mockry's site is not specific as to where that lamp can be
> hooked up to existing wiring.

More information about the quattro mailing list