Please assist me!

[Greg Baxter <gbaxter@valleybrook.com>]

I know that this isn't the A2 group, but my newsgroup access (actually, or 
entire internet server here at work is crappy, sorry if this is a double 
posting...) is sketchy at best, so I'm really hoping that someone can offer 
some insight. I'm having a bugger of a problem with my 91 Jetta, and I'm 
kinda hoping that I can get some insight from you all.

It's a 1.8 8v (digifant injection - black boxes - yech!) with the only mod 
being a K&N Cone filter.

The problem comes and goes, and is quite intermittent, but has happened 
more and more often in the past week. The weather is above freezing, but 
like the rest of the Pacific NW, quite wet.

(Usually) after the engine is warm, it will totally lose all power. I can 
floor it, and get the 'intake noise' that comes with the K&N but absolutely 
no power. It almost feels like I'm hitting the brake instead of the gas. 
The thing that concerns me most is the fact that it comes and goes so 
irregularly. It seems to worsen if I floor it, but if I have a light foot 
on the gas, it sometimes will limp along. If it's floored, it might drop 
the RPMs to 1000 or lower, and then suddenly BAM! Hard acceleration, or 
even worse, bucking.

I've thought about, and ruled out the following theories:

Cap, rotor, plugs (all replaced on the weekend) The air filter is OK (I 
just cleaned the K&N this summer, and it doesn't get driven in dusty areas) 
There doesn't seem to be any vacuum leaks, the hoses all look good. If the 
fuel filter was clogged, wouldn't the problem be more
persistent? Same with timing, or the fuel pump, right? I have recently put 
a couple of bottles of injector cleaner through, and I only run premium 
grade gas. The tank was 1/4 full when it happened on Friday, but it's full 
today, and happened to my wife again. (No problems for me this evening, but 
that's the nature of this problem...)

I don't want to take it to a shop, cuz they'll be looking through a whole 
bunch of theories at sixty bucks an hour, so I'd like to rule out as many 
potential problems as I can now. I am concerned that it might be my Air 
Flow Sensor (digifant part, most likely quite expensive... I'll be getting 
the multimeter out, and testing it this weekend...) I have a new fuel 
filter, which I'll install on Saturday, but like I said, if it was clogged, 
wouldn't it run lousy all of the time.

What are the symptoms of a clogged cat, or faulty Ox sensor?

Thanks everyone!


Greg
82 Scirocco (rear discs, seem to be sticking - hot rear wheels, but that's 
another problem for another day... sigh)
91 Jetta


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