Backfiring noise when accelerating?
Backfiring noise when accelerating?
Author
Discussion

scooby_doo_do

Original Poster:

137 posts

225 months

Saturday 30th May 2009
quotequote all
Noticed today that when i was accelerating say in third gear, there was a loud noise like engine backfire/popping when over 2k revs.

Just wondering what could be causing it? I noticed it did it in all the gears for about 3/4 miles till my destination.

When i left again, the problem had gone away, and it was not doing it?

Very odd...

GTRCLIVE

4,193 posts

312 months

Saturday 30th May 2009
quotequote all
Holley or FI, LS motor or SBC, If SBC is it MSD Disy or HEI.... now how many other abbreviations can I think of....

738 driver

1,202 posts

222 months

Saturday 30th May 2009
quotequote all
If your motor has a distributor, it is worth taking the cap off.......they seem to get neglected......Ideally should be quite clean inside and not a corroded shambles, as they can become!
Backfiring/spitting can be caused by several issues, the dizzy/cap/rotor being easy one's to start with.
Air leaks and fuelling next, sticking valves later.

Good luck.

scooby_doo_do

Original Poster:

137 posts

225 months

Saturday 30th May 2009
quotequote all
ok thanks,

It has a Dizzy on it, and a 4 port holley carb. Just seems odd that it did it for say 10 minutes of driving, then after a short break of 30 minutes, it was absoloutly fine.

I'll give the car a quick look over tommorrow and check all is ok.

Thanks

Craig.

V8Dom

3,547 posts

231 months

Monday 1st June 2009
quotequote all
craig
sounds like you have condensation/corrosion in the dizzy...

remove the cap and remove the advance plate... underneath there are the pickup coils and eight pickups that get corroded.

the condensation has dissapeared because the engine has got hot...

please clean up the pickups and coils..be carefull not to use emmery cloth as the gap should remain constant...
but if you dont clean off the corrosion the resistance will get higher and the gap smaller...once clean a quick squirt of wd 40...

Dom

Builder

1,225 posts

271 months

Monday 1st June 2009
quotequote all
Maybe too obvious, but had you washed the car or engine bay? Drive through a puddle? Had it been raining just recently? If so, it's not uncomon to get water/moisture in the ignition connections, dizzy, or spark plug wires. If you park the car for a few minutes after driving, the heat dries everything out. The problem seems to "evaporate".

Dielectric Grease from the local parts store (e.g. Permatex) can prevent water/moisture entry into electrical connections.

GTR-TT

442 posts

287 months

Monday 1st June 2009
quotequote all
If the engine leans out it often makes a popping sound. This could be a very expensive sound...

Edited by GTR-TT on Monday 1st June 07:52

scooby_doo_do

Original Poster:

137 posts

225 months

Tuesday 2nd June 2009
quotequote all
Ar, ok.. I had washed the car, but then it went to Mercedes for a week to do the MOT. Chap said it had just been started/stopped to be moved each day.

The other question, is about the "if the engine Leans out" - What does that mean? how can i test it? Don't want to do any damage to my toy!

Thanks for all the responces chaps..

Craig.

LuckyP

6,243 posts

254 months

Tuesday 2nd June 2009
quotequote all

GTR-TT

442 posts

287 months

Tuesday 2nd June 2009
quotequote all
scooby_doo_do said:
Ar, ok.. I had washed the car, but then it went to Mercedes for a week to do the MOT. Chap said it had just been started/stopped to be moved each day.

The other question, is about the "if the engine Leans out" - What does that mean? how can i test it? Don't want to do any damage to my toy!

Thanks for all the responces chaps..

Craig.
Sorry if I scared you... test it with a broad band lambda. If it leans out to the point that it starts to pop then you will see it instantly on the lamda.

qwick

530 posts

296 months

Tuesday 2nd June 2009
quotequote all
"Leaning out" means the air fuel ratio becomes more fuel than air hence it becomes "leaner". As it becomes leaner it combusts in a different way and usually gets very hot and in due course (not long at all) it'll melt valves and pistons and generally be a nuisance.ranting


V8Dom

3,547 posts

231 months

Tuesday 2nd June 2009
quotequote all
LuckyP said:
mmmmmmmmmmm see that car in the back ground???????mmmmmmm X8??????????

dom

Steve_D

13,802 posts

287 months

Wednesday 3rd June 2009
quotequote all
qwick said:
"Leaning out" means the air fuel ratio becomes more fuel than air hence it becomes "leaner". As it becomes leaner it combusts in a different way and usually gets very hot and in due course (not long at all) it'll melt valves and pistons and generally be a nuisance.ranting
Sorry, tother way round.

Leaner means to much air.

Steve

ezakimak

1,871 posts

265 months

Wednesday 3rd June 2009
quotequote all
V8Dom said:
LuckyP said:
mmmmmmmmmmm see that car in the back ground???????mmmmmmm X8??????????

dom
http://www.phormula.co.uk/UltimaGTR.aspx

edfoxuk

203 posts

259 months

Wednesday 3rd June 2009
quotequote all
its ignition, betya.

qwick

530 posts

296 months

Wednesday 3rd June 2009
quotequote all
Steve_D said:
qwick said:
"Leaning out" means the air fuel ratio becomes more fuel than air hence it becomes "leaner". As it becomes leaner it combusts in a different way and usually gets very hot and in due course (not long at all) it'll melt valves and pistons and generally be a nuisance.ranting
Sorry, tother way round.

Leaner means to much air.

Steve
Sorry Steve you are right, that's what I meant to write, thanks for correcting.

qwick

530 posts

296 months

Wednesday 3rd June 2009
quotequote all
Give the dizzy, coil, leads and plugs a good clean and set the plug gaps as a first start. Costs nothing and easy to do.

scooby_doo_do

Original Poster:

137 posts

225 months

Thursday 4th June 2009
quotequote all
thanks Guys.. I don't think it's running lean.. Not with the smell/petrol consumption that i get with the holley 4 port carb. But still i'll get that checked out.

My freind came over at the weekend who's been racing car's all his life and said he thinks the plugs are all choked up, and could probably do with a new set making sure the gaps are exactly right. He gave the dizzy a good clean, and checked over all the leads.

Popping's stopped now :-)