alindquist

I have a 2006 469 mag, DTS, that is spitting and sputtering at idle, it's missing, but not sure what cylinder and they didn't have enough time to properly check it. It does seem to run fine once you get on it. Service writer thinks it's possibly injectors, mechanic says it could be coil packs... Is there a good way to test coil packs? This has been going on for a while and doesn't seem to get any better or worse. The plugs were changed at the beginning of the season and that didn't fix it.
Any ideas?
Thanks,
Aaron

GO4BROKE

iTrader: (1)

Yes, get it some place to diagnose it for you. Everyone can guess all day, but without proper diagnosing, you will spend a fortune with no results. That said, coils usually act up under a load. Injectors usually are a problem through the whole rpm range. What code do you have? Many things can cause an idle miss. MAP sensor, vacuum leak, cam or crank sensors, plug wire (you should check to see if they are securely installed, they do sometimes work loose), valve train issues, etc.

cigrocket

iTrader: (3)

Iac

alindquist

That what they originally thought but the DTS motors do not have one...

BUP

iTrader: (9)

1000% all Mercruiser DTS do not have IAC's and they do not have IAC mufflers as I posted this info a bunch of times up here. .

A scan tool will show 4 sure bad coils. Has to be able to scan PCM 555

also sealed inline spark checkers and run the engine to watch spark events.

DO NOT test for spark any other way with app - 2 reasons mainly - open spark in a engine compartment plus gas fumes - do I need to say more and jumping spark off the engine for testing purposes can knock out the PCM. I know an owner who did this testing for spark and knock out his computer. Actually 2 owners in the past 6 years.

have no idea why the repair shop has not scanned your engine especially being a PCM 555 / 496 along with fuel pressure testing.

WHAT COOL FUEL IS THIS APP GEN II or GEN III 2006 was the trans year for the change thru Mercruiser. If it is GEN III I might know the problem.

alindquist

BUP, I was waiting for you to chime in... To be honest I don't know if it's genII or genIII. Serial number on that engine is 0W618145. The engine wasn't putting up any codes that would cause this. He was going to start trouble shooting it be we ran out of time (it was in the shop for an unrelated drive problem). I'll probably just bring it back to the shop in another month and have them start testing stuff but if you got any ideas I would be interested to here them.

BUP

iTrader: (9)

Not saying this is your exact problem but no codes can be this reason - read post number 5. Have no idea what happened to this guy. Threw him a bone here for free and texted him still nothing. Anyways read post 5

http://www.offshoreonly.com/forums/g...need-help.html

with that said you do have the crank sensor that is more prone to problems than the newer design. You might have the Gen 1 coils in which are prone to more problems and a bad coil(s) can or will knock out your PCM over time. Seen it I promise.

You do have the NLA cam sensor in which stinks but hopefully I have the fix for that - I DO NOT THINK THE CAM SENSOR IS YOUR PROBLEM

Back to the crank sensor yours - questions for U is there any loss of rpms especially at full throttle - next is how well is the tach working correctly and very steady readings from the tach ? Crank sensor is the tach signal here as well.

Have you Changed the spin on fuel water sep filter and looked at its fuel sample ? as you have the GEN II cool fuel design from your engine serial number.

Would not rule out the injectors and you have to fix the cause of what is contaminating the injectors in which very well could be internal corrosion of the fuel rails. They rust internally badly even in freshwater use. Just saying. Injectors would be a good guess here and being over a 10 year boat is very wise to have them checked out anyways. I do have the machine to do so FYI just in case but your decision who and services you wanted to use.

You can always do an injector balance test with the scan tool and or check resistance at the injector. Believe it or not I listen to the fuel injectors with a real doctors stethoscope while the engine is running. Amazing how you can hear a problem injector compared to the other ones.

Just saying for some of the ways I test things to rule out the possibilities plus of course I have the latest greatest scan tools for the marine side in which helps a lot. And I know how to read the scan & parameters very well & very important here. You can send me your scan report to if you like. Many people have done so and a lot of times more times than not - I have pin pointed their problem or lead them in the direction to keep testing to find it and they did. I would want a report with the engine running and at different rpms for a scanned report of your app.

alindquist

BUP - Thanks for the info, it's a lot to digest... When I'm between say 800 - 1200 RPM the port engine is surging, I'm not sure if this has something to do with the autosync on the DTS, it does not surge in gear and dead idle. From there to almost WFO the RPM's stay consistent, once I hit WFO the port engine is missing about 200 RMP's (based on what the starboard engine is getting, around 4400) and it's bouncing around about 50-75 RPM's + plus or minus but not getting over 4200 - 4300. I'll probably just bring it back to my mechanic in a few weeks and see if they can figure something out... From the sound of it i might be out of my league as far as a DIY on this...

BUP

iTrader: (9)

Possible crank sensor especially if you are down on some rpms. Careful taking it out as they can break off leaving a portion in the topside of the engine. The newer version is more stought as well.

And of course can be restriction and or contamination of the injectors