How to stop backfiring?

Post by **Onne** » Tue Mar 22, 2005 10:14 pm

My low compression 1098 is suffering from backfire when decellerating, whilsr using engine braking that is. she is using a lot of petrol too. any ideas? Vacuum advance is working. it is getting worse, and I have to travel for more than 250 miles next weekend (easter) I do not want to spend so much on fuel (currently about 25mpg)

Post by **rayofleamington** » Tue Mar 22, 2005 10:58 pm

suffering from backfire when decellerating,

backfiring or making the normal farting noises?

as for the poor MPG - what have you checked and which parts have you changed so far?

Post by **bmcecosse** » Wed Mar 23, 2005 9:02 pm

True back firing is when unburned petrol ignites in the exhaust - so it could be burned exhaust valves, or maybe just the tappets needing re-set ? Get a compression check done on the engine. If it's farting - just lay off the beans !! Seriously - maybe just increase the idle setting slightly to allow more gas to flow through the engine on over-run. Or do as i do - and slip it into neutral when going down hills.

Post by **rayofleamington** » Wed Mar 23, 2005 9:39 pm

Or do as i do - and slip it into neutral when going down hills.

nooooooooo

set the tickover very low, find a big hill and do 42mph all the way down with the foot off the gas, farting all the way down - it works best when there are houses on both sides as the noise resonates between them....

Post by **bmcecosse** » Wed Mar 23, 2005 9:44 pm

Really best at about 2am !!

Post by **Onne** » Wed Mar 23, 2005 10:37 pm

I am a fool. I thought I had turned up the idle a bit.... seemed to be the fule mixture screw... which explains poor fuel economy and the backfiring, as the mixture was set too rich. I am just a git. Got another problem now though. The rear offside is lower than the right... I'll just put up a new topic.

Post by **rayofleamington** » Wed Mar 23, 2005 10:49 pm

The rear offside is lower than the right... I'll just put up a new topic.

double check the front suspension first - this will make the rear look wonky

Post by **Onne** » Wed Mar 23, 2005 10:52 pm

Front looks ok. I was under the car 5 minutes ago, and i can hear the rear shock absorber making noise, and leaking a bit of oil. Still very drivable though. I will check the front with a tape measure now, and also the rear again.

Post by **Onne** » Wed Mar 23, 2005 10:56 pm

front, both sides 10" rear rhs 11" rear lhs 9 3/4"

Post by **rayofleamington** » Thu Mar 24, 2005 8:36 am

front, both sides 10" rear rhs 11" rear lhs 9 3/4"

oh! the shell must be a little twisted then ?

Post by **bmcecosse** » Thu Mar 24, 2005 7:12 pm

The car usually settles on the side where the driver sits - I am guessing this is a lhd car ? You can either fit a new spring - usual advice is to fit them in pairs - or just swap them over (which could well solve the problem) - or just fit longer shackles on the lower side spring. Just make them from 5/16" steel bar. Shackle 1" longer will lift the car about 2". However - you had better have a good look to see if in fact the problem is RUST where the springs meet the bodyshell - front and rear !

Post by **Onne** » Thu Mar 24, 2005 9:03 pm

rhd drive, and the shock absorber is leaking and squeeking. No rusty whatsoever on thebottom though