Damaged SOMETHING with backfiring ...

when trying to locate a running problem with the engine it is a good idea to
test the condition of the engine.

My definition
A compression test will determine how much the engine will compress air.
There are certain procedures to do this, such as disable ign system, remove
plugs, open throttle, crank over engine and watch compression gauge during
all strokes. The first stroke will be important also, so that needs to be
watched.

A leak down test, injecting a cylinder with air and watching a gauge, will
check how well the engine can hold that compression. Compressed air will
leak out via piston rings, valves and possibly elsewhere. It can help
determine where that leak is too. Piston needs to be at TDC in firing
position.

"Fred Mann" > wrote in message
...
>I don't know what a leak-down test is and I haven't done a compression
>test.
> Do I need to do both?
> Also, I can't seem to find the timing marks anywhere. I looked inside the
> port that is on the bell of the transmission and I didn't see any marks. I
> rolled the car in high gear and looked in there with a flashlight ---
> nothin'. Am I looking in the right place?

I'm going to check timing first since it should be easiest. BUT there is no
mark OR pointer. (I removed the plastic plug) I think I have found TDC on
piston 1 using the techniques above, but I still don't know how I'm going to
locate 6 degrees BTDC. I can put a dab of paint on the flywheel, but still,
I don't which way is "before" and which is "after" or how far 6 degrees is.
Also, do I need to pull the vacuum advance hose?
And as for the exhaust problem ... is it possible that a piece of the gasket
is stuck in the manifold? I was just wondering if I might have an exhaust
clog somewhere before the catalytic converter ....

Fred Mann wrote:
> Also, I can feel some pulsing air when I put my hand around the back side of
> the engine, so maybe this noise is some exhaust leak? But then why would I
> have a loss of power and why would it be isolated to #2 piston? Hmmmmm.....
>
> For # 2 cylinder, check compression, plug wire, fuel injector operation.

Compression test results:
I removed all plugs, put the pedal to the metal and cranked the engine. The
results were nearly identical for each cylinder.
First crank was roughly 95-100 PSI for each cyl.
After about 5 cranks, the guage leveled out around 175-180 PSI. I doubt
there was more than 5 PSI difference at any stage across the board.
I'm assuming this means my engine is okay. At least by this measure.
However, I am still operating with the rear half of the exhaust system
removed (catalytic converter and tailpipe disconnected). As is, I have seen
some smoke when I rev up the engine. Is this a sign of another problem, or
is this to be expected when the converter is removed?

PS -- I have not replaced the plugs, but I have replaced cap, rotor and
wires. One
of the towers on my newish rotor already had some damage -- pretty heavy
carbon deposits, and what appear to be a slightly displaced inner metal
sleeve

On Wed, 11 Jul 2007 16:08:02 -0400, "Fred Mann"
> wrote:

>I'm going to check timing first since it should be easiest. BUT there is no
>mark OR pointer. (I removed the plastic plug) I think I have found TDC on
>piston 1 using the techniques above, but I still don't know how I'm going to
>locate 6 degrees BTDC. I can put a dab of paint on the flywheel, but still,
>I don't which way is "before" and which is "after" or how far 6 degrees is.
>Also, do I need to pull the vacuum advance hose?
>And as for the exhaust problem ... is it possible that a piece of the gasket
>is stuck in the manifold? I was just wondering if I might have an exhaust
>clog somewhere before the catalytic converter ....
>
It is covered in the Bentley manual. See page 68. You do not have an
exhaust clog. Banish that idea from your mind.
http://cgi.ebay.com/ebaymotors/VW-Ra...spagenameZWDVW

Good now you can proceed to other issues like ignition, fuel exhaust, etc
since the engine passes the comp test..
Yes replace any known bad component to eliminate that as a possibility.
You have identified that #2 noise as an exhaust manifold/gasket leak.
Fix that if the tick is annoying or very loud.

And you think the loss of power is due to a clogged cat???
There are inexpensive "universal" cats out there or you can temporarily
install a test pipe on the exhaust in place of the cat. I vote you install
a bolt on cat and be done, unless you are not sure about having a bad cat.
;-)


"Fred Mann" > wrote in message
...
> Compression test results:
> I removed all plugs, put the pedal to the metal and cranked the engine.
> The
> results were nearly identical for each cylinder.
> First crank was roughly 95-100 PSI for each cyl.
> After about 5 cranks, the guage leveled out around 175-180 PSI. I doubt
> there was more than 5 PSI difference at any stage across the board.
> I'm assuming this means my engine is okay. At least by this measure.
> However, I am still operating with the rear half of the exhaust system
> removed (catalytic converter and tailpipe disconnected). As is, I have
> seen
> some smoke when I rev up the engine. Is this a sign of another problem, or
> is this to be expected when the converter is removed?
>
>
> PS -- I have not replaced the plugs, but I have replaced cap, rotor and
> wires. One
> of the towers on my newish rotor already had some damage -- pretty heavy
> carbon deposits, and what appear to be a slightly displaced inner metal
> sleeve
>
>

Well, I finally got my catalytic converter all the way off. I had to cut the
screws off with a dremel. Anyway, it's completely hollow. I'm not sure if
it's supposed to be like that. My concern is that the backfires blew some of
the "guts" of the CC down the pipe and possibly cause a clog there or in the
muffler.
Any thoughts?
Also, when I replaced the hall sender, I used an old one from my other
rabbit. I assume it's working fine since the car runs without cutting out
now (unlike before I replaced it). As far as I know, hall senders just send
a signal to the coil and it either works or it doesn't. That is, it can't
send a "weak" signal. But I just wanted to make sure that I didn't overlook
something or use an inferior part. Again, any thoughts would be greatly
appreciated!!!
Fred



"dave AKA vwdoc1" > wrote in message
t...
> Good now you can proceed to other issues like ignition, fuel exhaust, etc
> since the engine passes the comp test..
> Yes replace any known bad component to eliminate that as a possibility.
> You have identified that #2 noise as an exhaust manifold/gasket leak.
> Fix that if the tick is annoying or very loud.
>
> And you think the loss of power is due to a clogged cat???
> There are inexpensive "universal" cats out there or you can temporarily
> install a test pipe on the exhaust in place of the cat. I vote you
install
> a bolt on cat and be done, unless you are not sure about having a bad cat.
> ;-)
>
>
> "Fred Mann" > wrote in message
> ...
> > Compression test results:
> > I removed all plugs, put the pedal to the metal and cranked the engine.
> > The
> > results were nearly identical for each cylinder.
> > First crank was roughly 95-100 PSI for each cyl.
> > After about 5 cranks, the guage leveled out around 175-180 PSI. I doubt
> > there was more than 5 PSI difference at any stage across the board.
> > I'm assuming this means my engine is okay. At least by this measure.
> > However, I am still operating with the rear half of the exhaust system
> > removed (catalytic converter and tailpipe disconnected). As is, I have
> > seen
> > some smoke when I rev up the engine. Is this a sign of another problem,
or
> > is this to be expected when the converter is removed?
> >
> >
> > PS -- I have not replaced the plugs, but I have replaced cap, rotor and
> > wires. One
> > of the towers on my newish rotor already had some damage -- pretty heavy
> > carbon deposits, and what appear to be a slightly displaced inner metal
> > sleeve
> >
> >
>
>

"Fred Mann" > wrote in message
...
> Well, I finally got my catalytic converter all the way off. I had to cut
> the
> screws off with a dremel. Anyway, it's completely hollow. I'm not sure if
> it's supposed to be like that. My concern is that the backfires blew some
> of
> the "guts" of the CC down the pipe and possibly cause a clog there or in
> the
> muffler.

Shouldn't be hollow and yeah the guts could be plugging your mufflers.

> Any thoughts?

It's probably more than you wanted but could very well be time for a
cat-back exhaust.

On Mon, 16 Jul 2007 17:49:13 -0700, "Matt B." >
wrote:

>"Fred Mann" > wrote in message
...
>> Well, I finally got my catalytic converter all the way off. I had to cut
>> the
>> screws off with a dremel. Anyway, it's completely hollow. I'm not sure if
>> it's supposed to be like that. My concern is that the backfires blew some
>> of
>> the "guts" of the CC down the pipe and possibly cause a clog there or in
>> the
>> muffler.
>
>Shouldn't be hollow and yeah the guts could be plugging your mufflers.
>
>> Any thoughts?
>
>It's probably more than you wanted but could very well be time for a
>cat-back exhaust.
>
Old post to answer too. If it is completely hollow then somone
probably gutted it with a screwdriver. On my cars they tended to melt
down and chunks would break loose. Those chunks either rattled making
a noisy car noisier or the car would not run due to a corked up
exhaust.

The converter is supposed to look like a honeycomb. But the grid is a
lot smaller than the honycomb you buy at the store to chew on. The
holes might be .5 mm in size. Maybe it is a bit bigger but it is
fairly small. You can hold a good converter up to light and see
through it input to output. A failed one meaning one that has clogged
or melted down will not pass light or you will see melted parts. Go to
any parts store and ask to see a new one.

Do not put a new converter on until your car is running perfectly. You
will just destroy a converter in short order if the car is running
rich, lean, or if the camshaft or ignition timing is significantly
off. I prefered to get someone to attach a sniffing probe to the
sniffing port to make sure the mixture was correct before installing a
new converter. The procedure is in the Bentley. Since the converter is
hollow you could just exhaust sniff from the tailpipe. The challenge
is finding someone with an old style exhaust analyzer that will let
you work for 15 minutes.