496MAG to codes, but wont run W/O
 

I bought a 2002 Baja Boss 232 with the 496MAG. It ran great until some rough seas. I took it to the dealer to have them look at it. They said the #6 plug wire fell off and just put it back on. They ran it, said it ran great, but when I took it out it ran rougher than usual. It used to run out to the top end of the W/O range of 4800rpm. It wont run above 4400rpm now. It idles fine, sounds a little rough coming out of the hole and with power on. There is no beeps or codes. I changed the plugs and replaced a battery that was going bad.. Any suggestions, I'm lost on this one and haven't been able to figure it out. The engine has 180hrs on it and has been kept in outstanding condition.

-2nd Chance-

Check the ground on the engine (usally on the back of engine), if it is loose

496 trouble shooting 101
 

You can check the fuel filters and replace them if it has not been done recently. Check the fuel pressure at the 4400rpms you're getting at WOT. Should be about 41-43 psi under full load.
Also check the plug wires and make sure each coil is plugged to the plug in the cylinder in the same order down each side. If a couple of cylinders are swapped it will basically run on six cylinders rough and without full power.
A bad fuel injector on one or more cylinders can also create this condition. Look at each plug out of the engine after a good run and see if they all look like they are burning the same colors and look.
Just somethings you can check yourself and possibly find the issue.

Best Regards,
Ray @ Raylar

Raylar,
I checked and replaced the plugs. The #6 plug that I pulled out was blacker than normal and I thought that it was because of when the wire came off, but I will look at the fuel pressure. I just boggles my mind that it ran fine until the wire came off. I figured that just putting it back on should have fixed it.

-2nd Chance-

fIXX
 

When ever diagnosing a miss in a engine weather its marine or auto related and when i pull a sparkplug and see a black sparkplug 99% of the time its a bad injector..that motor is prone for bad injector once in a whyle..have a friend that his 496 would not go over 4400 rpms in a newer donzi zr with 46 hrs on it..black sparkplug and all,,he had the injector replaced and now he is back running on the rev limiter..

check to see if you have black soot around the transom when in use,or dirtier than normal when on the hose. sounds like a bad injector. check for 15.5 ohms at each injector...change out if readings are +/_ .5 ohms. I really am not buying the spark plug wire story.

Fixx
 

+1 but with the engine cold..

Pretty common on EFI marine engines that sit or are stored a lot over their life to have fuel system problems, especially injectors as the fuel system is subjected to a lot of moisture buildup and corrosion form sitting with ethanol additives in today's fuels.
If you run the injector test and its a shorted injector that's easy to find, however if the injector is sticking, gummed up or spraying weakly or badly it will cause a definite cylinder miss and this is more difficult to find. Probably best advice is to pull the fuel rail, remove the injectors and have them cleaned flowed and properly check. Its also importnat on certain year 496's to look for rusting inside the fuel rail itself from moisture sitting in the system. the rust will clog the injector fine inlet screens and stop them from working properly.

Best Regards,
Ray @ Raylar

I pulled the plugs again yesterday, after running it with the new ones in it and all looked fine except the same cylinder that was bad before. it looked pretty brown. I also took a resistance reading on the plug wires and found an 1 ohm difference between the the good cylinder and the bad one. Couldn't find any literature on what they should be. Raylar, I might be calling you for a set. I also changed the fuel filter yesterday and checked for any water. There was non, but I will check the injector readings and post what I find. :grinser010:

-2nd Chance-

Fixx
 

the ohmes may read that the injector is ok,,it may be clogged or the screen on top of the injector may be clogged and not leting fuel in,,take a long 2' screwdriver and put the steel end to the injector and the plastic handle to your ear and listen for a clocking sound,,no cliclk no work..also if you have a noid light remove the injector connector to make sure its getting power and injector pulse.. some pcm's will shut that injector circuit down if theirs a problem with it..

just as a side note, your digital volt meter may read a bit off from another one like it....so youy kind of have to use your jugdement on this. the injector should read approx 15.6 ohms (dependining on the meter used) anything +/_ .5 ohms means it is going bad.

Almost same problem I had this year...boat ran rough, RPMs capped and down on power...crawled around engine to find #8 plug wire in the bilge. I kept looking at this as the source of the problem, turned out to be an IAC failure. Not sure if the plug wire being off caused undue problems for the IAC, but a simple replace and all is good again. Thread located here: http://www.offshoreonly.com/forums/g...ing-rough.html

NAUGHTY,
Did yours throw a code?

-2nd Chance-

Not at first. There where codes saved, but nothing that pointed to the IAC. So we cleared the codes and I went back out on the water; it wasn't until the second time I brought it in that a single code was saved indicating a problem. If it wasn't for the hard guardian mode after a rapid removal of throttle, I'm not sure I would have known which motor or that there was a problem other than the loss of 6 mph from my top end.

Just an update to this forum. The motor has been fixed. I took it out on the water with a computer hooked up to it and the tech couldn't see anything. Sent all 8 injectors out to be cleaned and found out all of them were clogged to some degree. The dealer said that there was some bad gas going around the area and that he was having to do this to a lot of boats. Thanks for all the advice to those who replied.

I believe it....I've pulled mine on two occasions since new after finding on the first go around (while hunting down would eventually be a boost pump issue) that each injector had a very fine sandy brown or rust colored grit. I pop one at a time and tap it against the fuel rail to clear it, then pop it back into place reinstalling the individual clips. Not sure if the grit comes from the tank or is an effect of Ethanol on the fuel rail/system, but it definitely is something to check on these motors and reasonbly easy to do yourself when encountering a no-alarm grimlin issue like this.