[urq] Violent Misfire

[Buchholz, Steven]

... I had intended to reply to the post that made it through earlier ...
found a bunch of messages backed up for moderator approval ... finally able
to raise my head a little bit for air ... 

Let me preface my comments with a note that I'm not at all familiar with
troubleshooting the WR ... but I have been around its WX cousin for many
years ... 

Are you absolutely sure about the loss of spark comment?  I suspect it is a
"red herring" ... but more below ...

Is the car idling well at all?  I suspect that you've got a big air leak in
the intake tract between the airflow sensor plate and the engine.  Once the
engine sneezes into the intake it makes any issue all the more acute.  On
the WX there's a whole bunch of hoses that sit in the area between the
airbox and engine which are part of the metered intake section ... a leak
anywhere will screw up the mixture by allowing unmetered air in.  From my
experience, the hose that goes from the "igloo" on top of the airflow sensor
and goes down to the elbow at the turbo inlet is the most oft found culprit.


If the intake tract looks good, I'd then triple check the timing between the
crank and cam, and the distributor.  

I checked out the firing order against the crank timing, and according to my
calculations cylinders 1 and 5 are adjacent to each other ... cyl 1
nominally being at -0- and cylinder 5 firing at 72deg ATDC ... so perhaps
there is something to be said about the flywheel sensors ... I remain
skeptical, but you may want to look over the flywheel teeth to look for wear
or contamination, and try another sensor that senses the flywheel teeth.
You might also want to find someone with a MAC-01 who is willing to let you
try it in the car ...

Now ... if you had a WX, I'd tell you to check out the WGFV ... but you
don't have one of these.  It does raise the issue of system and control
pressure though ... be sure to get a fuel pressure gauge and confirm that
system and control pressure are in the proper range ... especially when the
engine is off idle ...

Good luck!
Steve B
San Jose, CA (USA)

> 
> A friend of mine without I-net access owns a very tidy 84 WR. 
> The car had been off the road for 13 years when he bought it 
> a year ago and he was told that the original owner (who had 
> since died) parked it up because it had developed a terrible 
> misfire shortly after having a new exhaust manifold fitted by 
> a VAG dealer.
> 
> When he got it running it seemed very smooth, yet under load 
> there was a bad misfire. After checking all the usual 
> suspects the HT leads, cap and rotor were changed and all was 
> well. This was about 150 miles ago. Then on a recent trip the 
> car had been running fine and smooth for a couple of hours 
> then stuttered violently and now has a serious misfire that 
> will not clear.
> 
> The curios thing with this misfire is that at idle No.1 
> cylinder has no spark. As the throttle is opened  No1 starts 
> sparking but No5 immediately loses it's spark. This happens 
> even at the smallest throttle openings.
> 
> What on earth can be causing this? I suspect a timing sensor 
> but which one and why? I only suspect this because most other 
> things have been checked.
> 
> Has anyone else suffered this?
> 
> If not any ideas how to cure it?