Have a 1997 challenger 1800, one engine backfires at about 2rpm. The other engine is running great, therefore good gas. Was running good, until this weekend, arghhh. Don't think the timing, fly and rotary, could have suddenly went out of whack. Thinking water getting into system so I resealed the exhaust at header and replaced the plugs, no effect. Anyone have any idea what I may check next on this backfiring 787?
787 backfiring at about 2 rpm
- Thread starter switt
- Start date
- Status
awdunn
Member
The only time I had a backfire issue was when I accidently over-gapped the spark plugs [gap too large.]
[ I assume that it occassionaly missed a spark, and on that stroke poured unburnt mixture into the exhaust, which then ignited upon mixing with hot exhaust bits from the other cylinder's exhaust. ]
Otherwise, I might [still] guess intermittant spark - try removing boot [screws off spark plug wire], cut off 1/4", screw back on. Thereafter, only part left would be the coil - or coil primary wire connections - below is one I recently took cover off, to find poor / intermittant connections on coil primaries. [Older GTI]
[ I assume that it occassionaly missed a spark, and on that stroke poured unburnt mixture into the exhaust, which then ignited upon mixing with hot exhaust bits from the other cylinder's exhaust. ]
Otherwise, I might [still] guess intermittant spark - try removing boot [screws off spark plug wire], cut off 1/4", screw back on. Thereafter, only part left would be the coil - or coil primary wire connections - below is one I recently took cover off, to find poor / intermittant connections on coil primaries. [Older GTI]
Thanks for the replies. Plugs not wet, replaced plugs, and cut back wires. Am afraid my problem isn't this easy. Reading other threads, I saw that a bad rotary valve could be the problem. Removed valve cover and see substantial scoring on both the cover and the engine valve surfaces. Fortunately, I have a rebuilt 800 setting in the garage for swap. Already have a carbon valve, but am not sure how am going rebuild/repair those scored surfaces. Believe that replacing the valve cover shouldn't be too expensive, but am stumped on the engine side. Am considering filling with something like JBweld or milling both surfaces and putting in a couple valves to take up the clearance. Any suggestions?
wernerml
Member
I had a 787 grenade on me and a needle bearing had become embedded in the rotary valve and made some nice gouges in the few revs it took the engine to stop.
The machine shop machined the surfaces of the rotary valve area, then removed some material from the lip of the valve cover/crankcase mating surface to bring the gap back into spec. I rebuilt again last fall due to water in the crankcase and the rotary valve and its gap all was fine.
The machine shop machined the surfaces of the rotary valve area, then removed some material from the lip of the valve cover/crankcase mating surface to bring the gap back into spec. I rebuilt again last fall due to water in the crankcase and the rotary valve and its gap all was fine.
- Status
Similar threads
