misses, backfires on top speed.

[TilliamWe]

Re: misses, backfires on top speed.

ok, so wash or no wash? not even when is dirty oily and all bad stuff, cant i wash just the engine bay as the guy said? or leave dirty forever?
can i apply wd40 every time i use?

Don't wash the engine. Wipe it down with a rag.

It shouldn't be oily and dirty. If it is, fix those issues.

Applying WD40 everytime you use it seems uneccessary to me.

 

[monterey98]

Re: misses, backfires on top speed.

i checked few conections right at the computer, main plug, few wires, they look good and dry, no corrosion.

im still need to figure out a way to test those sensors or find someone with a scanner or tool that can tell us if we have a code or not.

im still lost. lol

 

[Aloysius]

Re: misses, backfires on top speed.

High speed miss is almost always ignition related. However, if you have an individual runner fuel injection, you could be dropping an occasional injector pulse.

The tach is a pulse counter..it obviously is getting misinformation from somewhere. If the tach isn't getting an accurate pulse, neither is the engine management system.

Look for a bad ground also!

 

[TilliamWe]

Re: misses, backfires on top speed.

... However, if you have an individual runner fuel injection, you could be dropping an occasional injector pulse...

He doesn't, he's got TBI. They spray all the time.

 

[monterey98]

Re: misses, backfires on top speed.

ground? i had a ground problem before, the boat didnt want to crank, finally i retight the battery and got better, no problems after that.

i filed the fuel filter only with a can of seafoam, to clean injector and all, the tach didnt stop jumping.

my motor is a efi i think only 2 injectors right? could be fuel pump loosing pressure in high speed?

but what about missing before reaching top speed?

 

[monterey98]

Re: misses, backfires on top speed.

yup bubba, i agree.

i already spent $80 bucks in parts and didnt change nothing.

i will restart with the tach, hopefully i can find an easy fix without major engine problems.

 

[monterey98]

Re: misses, backfires on top speed.

hi there guys.

the mechanic found a purple wire not conected from the alternator.
is this the source of my whole problem?

 

[monterey98]

Re: misses, backfires on top speed.

hey guys.

i found 36psi of pressure, and all spark plugs fouled (wet), which sensor do i change? the computer must be getting wrong reading and sent too much fuel all the time.

the purple wire i found hanging must be for the tachometer, after installing correctly the tach reads more steady, i need to water test it.

but before that i want to fix the fuel problem.

any ideas guys?

thanks

 

[Aloysius]

Re: misses, backfires on top speed.

TBi..you'll never have a "miss" from TBI at high speed. Too much mixing in the plenum to isolate a cylinder missing. If it's going lean it will surge, not miss.

Injectors are pulsed to provide the necessary fuel..more fuel, longer the injector is open. The spray pattern appears constant because of this mixing in the throat/plenum. Just like a carburetor.

 

[monterey98]

Re: misses, backfires on top speed.

update guys is:

the thermostat valve was stuck wide open, install a new one and will take it for a ride tomorrow, pressure aint down, but the smell and plugs looks better, hopefully i wont start burning lots a fuel and my problem get solved.

 

[monterey98]

Re: misses, backfires on top speed.

well guys.

after changing the thermostat valve and all the tuneup parts, nothing change, unhooked the tach and still the same.

any opinion? thanks.

 

[teammadden]

Re: misses, backfires on top speed.

I am having the same symtoms with the same engine any luck on a solution yet? I have had no replys to my post.

 

[monterey98]

Re: misses, backfires on top speed.

hi teammadden.

i got no lucky too, people stoped responding my post.

i can tell you something i tried and you can try but in my case didnt work.
instead of buying a tool they sell online for $50 (a code reader) i found a post explain it how to make one for $3 dollars.

you basically need a resistor led light (radio shack) and a small paper clip, you connect them on the ecm outlet to read code if you have any.

i had 0 codes.

I changed and checked basically eveything and concluded that only happened every once in a while like yours, so i dont know what else to check, im lost on this one, its gotta be a fuel related problem, the pick up tube, the screen, the shyphon valve, something like that.

i will replace the tach to see if will stop at least the jumping, and i think i will have to use the boat as is with the missing/backfiring. lol, cant sell it, no one will buy. lol

please teammadden let me know if you find the solution.

thanks

 

[monterey98]

Re: misses, backfires on top speed.

by the way, this if how you make the paper clip check thing.
let me know if you need help to read the codes.

http://www.offshoreonly.com/forums/...ke-marine-efi-code-tool-less-than-1-00-a.html

 

[Haffiman]

Re: misses, backfires on top speed.

At the very first post it was said:

'and when i play with the trim up to get top speed, i hear popping/backfiring noise coming from the engine, dont '

Somewhere in the electrical system it is a faulty B+ or ground.

Hook a voltmeter directly on the Ign+ feeding the ignition and the Neg for the ignition (Not on block, but cable itself)

Run and see if there is a voltage drop to the module/ign when trimming.

 

[christoner2002]

Re: misses, backfires on top speed.

Does it run good for awhile at top speed, when you first take it out? Then, as it warms up, say a hour of running or so, start acting up? I chased that problem for awhile with my 350 Carbed. I ended up finding the Ignition coil was overheating, and breaking up the ignition at high rpm, causing it to backfire, and pop. Just a thought! (edit. Just looked up your coil, and it is a totally different style then mine, so I don't know if that would be the problem edit)

 

[teammadden]

Re: misses, backfires on top speed.

Thanks for the info, I did buy the diagnostic tool and have a manual to read the codes, there were some codes from the sensors but I believe thats because we removed them while trouble shooting. I have cleared the codes and will use the diagnostic tool to set my base timing and I hope to run in the next few weeks before I winterize to see if any codes comes back. below is a list of what I have done. Please keep me posted if you find any thing out and I'll do the same.
New Plugs
New Plug wires
New Dist. Coil
New Dist. Cap, Rotor and sensor wheel
Drained Gas tank cleaned pickup
Gas tank vent clear
New gas
Replace anti-siphon valve
New water seperator filter
Fuel pressure checked ok
Checked resistance on air temp sensor ok
Checked resistance on engine temp sensor ok

 

[monterey98]

Re: misses, backfires on top speed.

man you did pretty much everything needed to be done.

i just will give up, in my case i have no codes.

the problem now happens every time, cold or hot, only under load, first thing i did when i got this boat was change the batteries, do you all think i do have a bad ground somewhere?

why show 0 codes in my diagnostic?

thanks

 

[christoner2002]

Re: misses, backfires on top speed.

Have you done a compression test? Mine sputtered and popped
when I first got it. Did a compression test and found 3 cylinders
quite low. I had 3 burnt intake valves. Guy before me skied with the
boat all the time. Check all 8, and they sould be within 10% of each
other. I think. If you don't have a compression tester, Autozone rents
them. When I first started having problems, I was told to go in the order
of, mechanical, ignition, fuel. If the plugs are easily accessable, it can't
hurt to check the compression. Good luck to you!

 

[monterey98]

Re: misses, backfires on top speed.

already checked compression, 180 psi all the way.

dont know what else could be, i dont want to take to "professional" to charge me $100 for diagnostics + $100 water test, to say that he dont know what is it.

computer says no codes, so, what else can i do, im about to winterize it.