Hey all,

I've had a problem for quite a while, the car would run really well sometimes, and bad others........As far as i could work out, it was temperature related, until the other day....

I had my rear muffler replaced with a straight through pipe (it is A LOT cheaper)...Guess what? The car runs well the whole time now, and the fuel mixture is nearly spot on all the time (i've installed an LED in the dash from the computers mixture signal, flashes continuously when the mixture is right....) After i picked up my rear muffler (it is EXTREMELY heavy for a metal cylinder with a few pipes in it....when you drop it it sounds very solid)...when i looked inside the muffler, there is a fair bit of carbon in it....a large amount actually....which got me thinking....Cold damp mornings would lead to the carbon being very "cloggy", until the muffler got hot enough to burn off the moisture....I haven't cut my muffler open to see inside, to test my theory (i am gonna keep it, in case the cops in australia don't like the exhaust!!)...but straight after i left the car place (midas), the car was revving A LOT4smoother.....My rear muffler was the original one from 1988, so i imagine, large amounts of carbon build up is highly possible....But just from the weight of the muffler, i'd say there was a fair bit in there!!!

Just for all your info, but the car is noticably freeer revving now that the muffler is removed and a pipe is there instead (the car sounds VERY sweet now, has the "burble" when decellerating.....very nice sounding when you hit about 5k rpms.....hhhhhhrrrrrrmmmmmm.....

See ya all

Aaron

/// If you find out that the muffler does have a build up post what you find. I doubt that the gas in upside down land is the same as the formulations here but the prospect is interesting.

Did you ever have trouble when going from high speed to stop and idle? Did the car die when that combination occurred?

Hey,

I am seriously considering taking an angle grinder to the muffler, but i looked inside it today with a torch, and from what i can tell, the inside of the muffler contains some sort of synthetic type material.. (Is this right? If you know, tell me!!)...This would, over the years clog up with carbon....the fuel down here is, well, crap....that would be the only description that i could give it...our octane ratings for most fuel is no where near equivalent to american ones...i would guess the car has been run on regular all it's life (something like 87-88 octane here) and it has had a rich running problem in the past (o2 sensor replaced by previous owner), which means that extra carbon would have been dumped in..... I don't/didn't drive the car very hard at all, but it doesn't use any oil at all, and doesn't leave a trail of blue smoke. But, something someone did observe is that when i haven't driven the car hard for a while, and i revved it through to 5500rpm, it would blow a bit of soot out the exhaust, not SMOKE, but SOOT....Which led me to conclude there must be a fair bit in the muffler....which i am also going to weigh to see how heavy it is... not light..... But when/if i cut the muffler open i'll post what i find. I did actually find the car struggling to run well after a high speed run (after about 30mins, and going to a stop...) even if i revved it hard in 1st and 2nd, it would idle low for a while... It never stalled though (manual trans, could that have something to do with it?)... I ran the car up a hill near here today (Barclay Road, North Rocks for those who live in sydney!), and was pulling 5000-5500rpms in 2nd gear for about 10-15 seconds, and not even a puff of smoke of any sort....so i am convinced it is/was my rear muffler causing the problem.... I imagine the better the fuel is that you run, the longer it would take for a muffler to clog.

Has anyone else had any experience with this?

All input appreciated!

Azza

/// Generally mufflers are "heavy" because they contain multiple pipes designed to delay and change the pulses from the engine. Designs differ but some have slots with chambers designed to work like a silencer for a hand gun.

In the US we have a product called a "glass pack" (spelling differs with manufacturer). This is a slotted straight pipe with fiberglass packed between the center pipe and the outer cover. They produce a mellow rumble, at least on my 73 144 twenty years ago. I put a short GlasPac instead of the resonater in the tail pipe.

My experience was that the glass fiber falls apart and the pipe rusts to the point that it rattles in te cover.

I never had carbon accumulation. Try pulling the test plug infront of the cat. Look for carbon.

I have a theory that at high speed a slight restriction would allow pressure to build in the exhaust. When the car comes to a quick stop the pressure can not be overcome by the idling engine and the engine stalls. the restriction allows the exhaust to depleat the pressure so the car would crank and run normally until the next high speed run.

Do repost what you find.