I have a VW Bora with misfiring problem and rattle from exhaust.

Sent to VW </question-list.aspx?FID=33> Experts December 27 2008 at
8:47 PM

I have a VW Bora with misfiring problem and rattle from exhaust.
Not sure if they are connected, i.e. if catalytic converter has
decayed
and is affectiing ignition.
I changed the spark plugs and also put jet cleaner into the last tank
of
fuel.
The problem persists and there is no dashboard alert.
It is worst when climbing hills - i.e. there is no power and I have to
force the gear change.
I have seen vague posts on the Internet about faulty coil packs and
was
wondering if there was an easy way to check this?

Optional Information:
2002 Volkswagen Bora 2.0L Petrol

Already Tried:
I changed the spark plugs. The old ones look similar, i.e. I don't see
that it's only one cylinder is misfiring.
I also put some injector cleaner in the last tank of petrol.
/p>

Malc659,

Which engine do you have in your vehicle and is the check engine light
on?

Danny

Your Reply
December 27 2008 at 8:51 PM (2 minutes and 48 seconds later)

It is VW Bora 2002. 2.0L engine petrol automatic. The dashboard is
clear
- no warning lights are coming on.

It does sound a bit like a clogged catalytic converter, although I'm
unsure why it hasn't thrown a fault for it. The cat is held to the
exhaust manifold only by 4 nuts.

This doesn't seem like misfiring to me, if you were misfiring you
would
have a check engine light. It actually seems like maybe your mass
airflow sensor is bad.

Try unplugging the mass air flow sensor and see if it gets better.

Danny

Your Reply
December 27 2008 at 8:58 PM (41 seconds later)

OK where do I find the mass airflow sensor?

The mass airflow sensor is on the air filter housing, it has an
electrical connection on it where the intake pipe attaches to the air
filter housing. Try disconnecting it.

Danny

So this sensor senses the amount of air being drawn into the air
filter
and is connected to the intake pipe that goes into the air filter?
I'll
go and try it.

Your Reply
December 28 2008 at 6:59 AM (9 hours and 57 minutes and 56 seconds
later)

Elo. I disconnected the sensor and there was no change in the engine
so
I think you are right. I'm going to do a bit of dismantling and see if
there is any obstructions but I suppose I have to buy a new sensor.

No, if you remove the connector and it doesn't change anything then
it's
NOT the MAF. I suspect it's your catalytic converter, I would drop the
exhaust from the manifold and see if it makes it better. I think you
may
have a plugged cat.

Danny

OK I'll try disconnecting the exhaust. What do you mean by a 'plugged
cat'? Actually it sounds like the exhaust is blocked - you know? I
thought it was the cat to start with because of the rattling noise.
Thanks for your MAF advice tho' - I won't buy one yet.

Your Reply
December 28 2008 at 11:57 PM (5 hours and 37 minutes and 53 seconds
later)

elo again. I got the cat fixed but now the misfire is worse so I'm
gonna
replace the HT leads. if that doesn't work i will have to pay for
dealer
to diagnose.

Your Reply

Elo. Just letting you know that I replaced the HT leads and all is now
well! BTW, whilst I was making sure that none of the leads was making
contact with any metal engine parts, I noticed a small tube running
normal to the #1 lead (LHS one). I think it may have become
disconnected
so I connected that also whilst replacing the HT leads. I have a
feeling
that little tube was important, because I remember a friend of mine
had
a Bora years ago and he told me the whole engine failed because a pipe
had come off (it was a diesel tho').