Jsoderbe...did you resolve your ping/knock issue. My mercruiser 5.7 EFI is doing the exact same thing. The only way I could get my boat on plane was to retard the timing to get rid of the pinging/knock issue, and then set back timing when on plane. I know that is not the solution, but I tried everything to resolve it. Manifolds are cool, distributor cap, rotor, wires, plugs, knock sensor all replaced. No codes showing with code reader. Any advice would be much appreciated as I am in a very remote location with no access to mechanics.

DO NOT MESS WITH THE TIMING. THAT is not the issue. When knock is sensed it automatically retards the timing, which makes the motor sluggish and lazy. You likely have an injector issue. Pull, clean and flow test the injectors. One or more are likely leaning out, causing knock, which reduces timing and makes the motor sluggish. None of that will show up on any code scan unless you are using Scanner Pro and monitoring knock retard etc.

Hi,

Sorry to say that I believe you are looking at either a burnt valve or (as I did) a blown head gasket. Dont drive too long, I had to pull the engine to resurface the engine block an head since I used it for another couple of hours.

A simple compression check would reveal what you are looking at. Cost maybe 50 bucks. If you run it too long you are looking at a $4000 repair instead of maybe $750 to pull the head on the pinging cylinder bank.

I havent heard of a clogged injector causing pinging, but I guess it could happen.


Regards,
Johan

It absolutely can and does. If the injector doesn't flow what it was programmed to it will lean out that cylinder. Leaning out the cylinder will often cause knock and elevate combustion temps. Knock sensor will retard timing in attempt to bring knock under control. This will exacerbate the exhaust temp issue by delaying the combustion event and heating up the exhaust valve and seat. Prolonged operation will in most cases yield cylinder specific damage, anywhere from damaged pistons, tulip'd valves, or dropped valve seats or all of the above.

The insidious part is that there is no injector feed back, you merely get the symptoms and start looking for the wrong problem.

the fuel injectors are the end of the line and are often over looked. Currently for marine apps fuel injectors are listed as regular maintenance to have tested and or flow tested along with basket filters changed if applicable. This currently is listed at least every 7 years min or sooner.

The sooner requirements for fuel injector testing / cleaning and so on are if water is present in the fuel system - or corrosion in the fuel system or contaminates in the fuel system or even poor engine running conditions especially noticed lean conditions. Engine rebuilds and performance upgrades

Not saying this is your pin point problem but is often over looked as well.

Thanks all for replies...recent compression test was good. Gonna look at the injectors next. Just never thought about it as I had a new fuel pump installed just days before my issues, but maybe something was jarred loose and injectors are partially plugged??? Thanks for pointing me in that direction Trash & Bup. Is there a fuel filter prior to the throttle body and if so where? Also found a post talking about a faulty shift interrupt switch causing similar symptoms as mine as it is linked to the ECM??? Gonna try bypassing it to see what happens. What do you think?