Thread: Intake backfire ?

Vacuum leak either in the gas line to the mixer, somewhere between the mixer and the butterfly or on the plenum. Since it's a 92, check the cold start piping as a main offender.

Yes but WHAT plugs, leads and ignition module, what plug gap, what coil, what timing advance, are the mixtures properly adjusted, what is the clearance between the rotor button and the cap contacts, are the leads spaced apart instead of tied in bundles etc. Just because tune-up stuff is new doesn't mean it's optimum for gas.

Follow Langy's advice and check for blown off hoses too.

Happened to me once. Melted 1/2 the carby on my 308. Metal everywhere even inside engine

Gary

Blows the lid off the air cleaner on the Mitsy vans,breaks all the clips,nothing a couple of ocky straps couldn't fix

Leads were often the culprit,we actually found the genuine ones were the go.

Happened to a mates P38, blew apart a fair bit of the inlet piping, he did get it fitted on the cheap though...

Cheers,
Nova

the leads and plugs are bosch with a lower heat and a bosch ing module the plug gap is .7mm

Timing should be 10 degrees BTDC at idle, make sure the leads are separated by 20mm not bundled together, if the intake backfire happens at light throttle (not full throttle) you may have set up the Bosch module wires wrong, the pickup wires may be reversed. If the pickup wires are back to front the timing will cause it to fire when the rotor button is neatly past the terminal in the cap and the gap is widening fast.

If you lay a rotor button sideways in the cap you can line up the centre button mark and see how much gap there is between the rotor and the cap. If it exceeds 1mm you need to either find a better rotor or gently peen the brass end on a block of steel. It's a fiddly process but worth it if your rotor is like new. You need to keep enough clearance so the rotor doesn't snag the cap and break.