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Miss/backfire?

1K views 9 replies 5 participants last post by  foxracer1 
#1 ·
My 86 2.5 has a bad intermitent miss low to mid range while under load. I have new plugs, wires, cap, rotor, Ing module, 6al, adj timming control, msd coil. What gives? This is very annoying. I have a sbc laying a around i'm going to slap some heads on it and put the t56 i got behind it and lay the poor 2.5 to rest after 170,00 gruling miles.
 
#4 ·
Well it did it with the several sets of plugs just put a brand new set in at the time of the ing module. Also the fuel filter is fairly new. but i could check the filter. thanks guys anyother suggestions.
 
#5 ·
assuming its tbi (im not sure of the exact years that had carb and tbi)

how old is the injector? i just replaced mine and got an extra 100kms on my last tank. also, is there an O2 sensor? it could be worn and getting a false reading, dumping fuel because of it. Backfires usually result in very poor timing or excessive gas at rpms.
 
#6 ·
I suspect the injector. How much are those? O2 is fairly new.
 
#7 ·
foxracer1 said:
My 86 2.5 has a bad intermitent miss low to mid range while under load. I have new plugs, wires, cap, rotor, Ing module, 6al, adj timming control, msd coil. What gives? This is very annoying. I have a sbc laying a around i'm going to slap some heads on it and put the t56 i got behind it and lay the poor 2.5 to rest after 170,00 gruling miles.
Carbon build-up on the valves maybe the annoyance.

Hold a tissue or paper towel at the tail pipe (while at idle). If it appears that it is being 'sucked' in, valve/s are not seating. The 170,000 miles on the 2.5 power plant is a factor.

Additives in the fuel tank would be helpful to remove any carbon on the valves / combustion chambers. (Marvel Mystery Oil Berryman ChemTool Sea Foam)
Select one of these additives.

That's the name of that tune !
 
#8 ·
I did the valves and had the head milled .009 about two years ago. top end should be good. i've even tried the additives.
 
#10 ·
Thats the prob no codes what so ever :rant:
 
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