Engine/Transmission (1994 - 1998) low power, back fire? blue smoke, what is it?

[GMichaels]

Have a 97 3500 4wd 4:10 5 speed with 209k. no mods



The problem started with low power, no black smoke. so installed boost guage and can get 25 psi. check fuel pressure, was low 12 at idle max 20 at 2500rpm. I replaced the overflow valve as well as the filter, and cleaned the prescreen. fuel pressure came up 5 psi so max is at 25 psi.



with the engine warm, if I mash on the gas the engine will stumble and backfire?? (not sure if diesel can backfire) and a cloud of blue smoke will appear. If I ramp up quick to 2500rpm no problem and run very smooth.



so I have a fuel plate and gsk to install but wanted the truck to be running right before i proceed.



So I am looking for help on what to do/try next, everything looks good. no air leaks at the afc line, fuel lines look good as well, no cracks that I can find.



engine has no blow by, I don't think its whipped yet, so figure I missing something simple.

 

[RoadGoesOnForever]

Check your timing assuming it does this when the engine is warmed up. Mine does this when very cold out in the first minute or two of driving, but after that is should not happen.

 

[WDixon27]

mine would do most of that till i set the timing last weekend, mine backfired too occasionally it turns out the timing was set to around 11-11. 5 degrees and i bumped it up to 16, now i am running a good 150 degree lower egts at interstate speeds plus it has low to mid range power now, i haven't put enough miles to tell what my mileage is now but my former best was 15. 2 with lots of interstate but after about 150 miles id say it's improved from looking at where the gauge is sitting

 

[Greenleaf]

My 12 valves (bus fleet) will do that too. Always white smoke. Never blue.



They are worst when cold but do it warm as well. The engine must be HOT to clear this symptom. I mean like, 180° or better.



What is does is run rough,sputter, back fire and has a WOT speed of 2000 rpm or so.



GL

 

[cahammer]

maybe a bad injector just my . 02

 

[cojhl2]

When you gusy say "Backfire" I hope you dont mean an actual fire back thru the intake system doya??



Holy backfire batman,, I did not think a diesel could do that!!



I always thot that sputtering like pulling tractors and trucks was just misfires//



Do I need enlightenment? Wont be the first time.

 

[WDixon27]

i had a couple backfires out the exhaust while trying to motivate the pig through traffic before he was warmed up and happy, i didn't think a diesel would do it ether till it did it a second time, i guess with enough egts and fuel vapor present in the pipe kapow, with the timing advanced all of that crap is gone and it's running great even cold, i don't need to idle through the gears to get down my street in the morning

When you gusy say "Backfire" I hope you dont mean an actual fire back thru the intake system doya?.

 

[RoadGoesOnForever]

When you gusy say "Backfire" I hope you dont mean an actual fire back thru the intake system doya??



Holy backfire batman,, I did not think a diesel could do that!!



I always thot that sputtering like pulling tractors and trucks was just misfires//



Do I need enlightenment? Wont be the first time.

You are right, misfire is the correct term, but most of us that have experienced this know what he meant.

 

[sardoghauler]

ford 6. 0?



Did i get the riddle right?

 

[cojhl2]

You know,, thts right! What we call backfires are exhaust explosions.



Where I went astray was when I read "backfire" all I could see in my minds eye was a ball of flame shooting up thru the carburetor. I never went on to think about it in the vernacular we all use.



With that straightend out, can a diesel cause an exhaust explosion or are we still talking only about the exhaust noise due to misfires.



Hope you guys dont mind me asking these questions im just trying to accumulate as much knowledge as possible.



edit: Whoops,, I just went back and read WDixon27 and he did have actual explosions in the exhaust. I guess my question is answered!! Im surprised to say the least!