backfiring FJ60

[et3surge]

So I am driving down the road and every "blue moon" my truck backfires. This is a daily driver, so I know its only occassionally that it happens in fact every 4-5-7 days.. I know that timing can have a lot to do with this but why so rarely. Also, seems to happen when downshifting from 3rd to 2nd gear more often than ever. Ideas? I do believe it is a backfire that is not happening in the engine but instead due to gas build up in exhaust system but what is the tell tale sign of that, is there one?

Crossposted at CCOT

Thanks all

 

[dd113]

Pull plugs and wires make sure you are not crossing wires and getting an intermittent backfire. Run OEM chcks on the HIC system.

 

[swank60]

I'd look around for vac leaks, too (just in case)

 

[Doc]

interestingly, I can 'coax' mine into backfiring if I have just pushed the choke in, then let off the gas to shift- it'll make a very soft pop.

I suppose that's left overs from running rich still...