1986 240 DL Engine sound like a VW now

Hi, last week I started to hear a sporatic sputtering, especially when I
drove next to a wall, or divider etc. The car still seemed fine though.
I rarely drive my car on the freeway but, tonight I decided to go shoopping
a few cities away.
Got there fine, but on the way home, on the freeway I noticed the engine
making that sputtering sound for a moment,(almost like a VW).
The car almost died just a few blocks from my home, but made it.
The engine used to run smooth, not much noticable noise, but now it sounds
loud like a volkswagon.
I admit I have'nt had a tune up in a while, but I was wondering what is
going wrong.
Any advice is very appreciated.

 

I think it is two things - a failing muffler (or other exhaust parts) and
need of a tune up. The exhaust system is easy to check - listen under the
car for a puttering sound, or roar if it is bad enough.

Mike

 

Thanks

 

Very hard to tell--could be some water in the gas or a very small exhaust
system leak, could be something else....

 

Well, today started the car for the first time today and drove it about 1
mile from my house and all of a sudden I heard a loud pop from under the
hood, turns out that one of the spark plugs popped out. It was hanging
there, so i pulled it out and it was like melted at the thread.
I talked to a guy today and he said it could be oil pressure is too high.
So, I'm gonna replace all spark plugs and get an oil change. Hopefully that
will do for now.

 

A damaged spark plug thread that leaks under combustion can be noisey
in a way that I suppose could be described as VW-like.

I don't like to dampen your spirits, but I'd be seriously interested
to know how oil pressure could affect the spark plug thread. It may be
that the guy you talked too had his mind on other things.

What I'm guessing is - the 'melted thread' effect is caused by the
thread being stripped out of the head, which has been cause by a
careless mechanic overtightening the plug. Although to get to the
stage where the plug just pops out means this has been done very
carelessly indeed.

It can probably be repaired with an insert of some sort (eg Helicoil),
but this will almost certainly require the head to be removed. I
expect you will find out when you try to put a new plug in the hole -
you won't be able to get it to tighten.

Try to avoid driving the car with a missing spark plug. You will not
only make a mess of things under the bonnet, but you may damage the
crankshaft, which will have an unrestrained load on one cylinder.
--

Stewart Hargrave


For email, replace 'SpamOnlyToHere' with my name

 

There's no way oil pressure has anything to do with the spark plug, if
that's what the mechanic honestly thinks then you need to find a new
mechanic.

If the plug is actually melted then that cylinder may have been running very
lean and will probably have burned valves. As another poster said though it
may just be stripped out. Sometimes with care you can get a plug to thread
in and tighten if the problem was caused by someone crossthreading it.
Otherwise you'll have to helicoil it or (recommended) replace the head with
a good one from a junkyard.

 

It's more likely the vehicle not firing on all cyclinders. The "sounds like
a VW" is the giveaway symptom.

alan

 

Well he said one of the spark plugs fell out, I would say it's pretty safe
to assume it's not firing on that cylinder at least.

 

When this happened to my Lotus with a Renault 16 engine, I removed the head
and took it to a cylinder head shop in Phoenix I later came to trust
(Arizona Cylinder Head, for the locals). They recognized it as a Renault
head when I carried it in, and told me it could be helicoiled. They also
said aluminum heads don't have to be removed to be helicoiled - the shavings
blow out through the exhaust. Of course, that was before catalytics. Another
method I've heard of is to run the piston to BDC (beginning of the
compression stroke) and fill the cylinder with shaving cream. Tap the hole
and pull the engine through the compression stroke to push the shaving cream
out the spark plug hole, carrying the debris with it. I can't vouch for
either method myself, but it might be worth the research. DIY tap and coil
kits are widely available in auto parts stores.

BTW, stripped spark plug threads are common in aluminum heads. Using
antiseize on the plug threads and a torque wrench to tighten them are your
best insurance against more of the same.

Mike

 

Heh! I've not heard of this use for shaving cream before. It sounds
plausible. The method I heard was to pack the flutes of the tap with
grease to hold the swarf, but I wasn't convinced it would work.

They are, but IME cost more than a single insert at a workshop. If you
have to do this more than once, and want to do it yourself it may be
worth the investment.

I reckon that spark plugs are the most over tightened item on the car.
They are the thing that many people will have a go at changing
themselves, and thinking they are doing the right thing, swing on the
wrench like it was a wheel nut, over stressing the threads. A plug
change or two later, and it mysteriously won't tighten properly. They
would have got away with this in an iron head, but not an ally one.
You really don't need to apply much force to seat a plug properly.
--

Stewart Hargrave


For email, replace 'SpamOnlyToHere' with my name

 

I've heard of the grease method too, but the shaving cream one is new to
me.

The guy that used to be a tenant in my neighbour's basement was out
changing the spark plugs and air filter in his Sentra. A couple of
hours later, I heard an anguished cry - "Why does this damn car run
worse now that I've changed the air filter and spark plugs?!" So, being
a nice guy, I walked over and asked (while listening to a car running on
3 cylinders), "Did you gap the plugs?" "Gap the plugs - what's that?"
Sure enough, one had been dropped, there was no gap at all! Some people
actually hurt their car by trying to do maintenance - and even worse,
"professional" mechanics are often no better.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

When I started using a torque wrench on the spark plugs I was amazed how
little torque 25 ft-lbs is. The threads on a spark plug make it look large
and stout, but it gets torqued down like a small screw.

Mike

 

Replaced all spark plugs today.
Drove it 10 miles roundtrip, back to normal.
Thanks.

 

My guess - cracked exhaust manifold. The performance problems are
because the O2 sensor is near the cat, downline from the crack/hole.

 

Yep. Finger-tight and then something like 1/16th-1/8th a turn is
all you need. I'm amazed they don't use a bayonet type setup
instead.

Me? I buy my plugs pre-gapped.(NGK and a few others come
this way) - double-check and install.

 

Well yesterday the same spark plug popped out again.
It's definetly stripped.
I put some antiseize on a new spark plug in, and i was able to drive home.
But now I'm not so shure about driving around.
How reliable is the antiseize method.

 

Antiseize is to PREVENT stripping the threads. Your threads are already
gone--what is done in this sort of case is that a slightly larger hole is
cut into the metal of the head and a insert threads into the newly enlarged
hole. The plug threads into the insert.

This is a job for a skilled person--I have seen it done when I was working
in various garages, however I would not try it myself--YMMV!

 

I had a feeling you were being over optimistic. But worth a try.

The anti-seize paste is not a way of dealing with a stripped thread;
it just makes it easy the undo something that may be subject to
seizing up. Some people advocate putting it on sparkplugs before they
fit them, because a seized plug can be a major problem to get out.

I'm afaird the only answer to a stripped thread is an insert. Helicoil
is the most common type, and most automotive workshops will be able to
do it for you.
--

Stewart Hargrave


For email, replace 'SpamOnlyToHere' with my name