Knock Sensor

[jaypoland]

I have a 94 SNOB with the computer ignition and have been having problems with the knock sensor hitting at about 3300 rpm. It sets the engine in safe mode until I shut down and re-start. Im burning high octane fuel and have replaced the plugs. Anyone with suggestions from here??

[wburg64]

Sometimes knock sensors will pick up other noises within the the engine, lean mixtures, high temp, lifter, etc. It certainley is telling you something.

[tryan]

start the motor at night to see if you have any errant sparks from the plug wires or arching at the coil pack. you might be able to hear it if you have a good ear. you can use a spray bottle with water, spray the plug wires and notice any drop in rpm. are any of the plug wire ends green or corroded?

did your old plugs look healthy? sometimes you need to burp the plug end boots when you re-install the wires. trapped air can sometimes push a wire off.

check the primary and secondary resistence ( generally a 10:1 ratio) of your coils and clean any grounds for the module and the pack. check your voltage and make sure your not over-volting at high rpms.



i would not drive it untill you find the problem.

[jaypoland]

ok, thats a good starting point. I checked the wires already and the old plugs looked good. The coil is a good possibility. It ran fine end of last summer, just started first trip this year. I appreciate the help

[Air206]

We had a limp mode condition - with no problems! The temp sensor was bad and threw it into limp mode. It was a sudden failure with the temp suddenly pegging then staying pegged when electronics powered. Engine started and ran well until sesnor flamed out at about 3,000 RPM. I would evaluate iyours at idle and begin looking at sensors. Our condition happened at 10 engine hours hrs on a 92 SN - I bet your sensors have a bit more hours on them. Be safe w/ the engine - but check for bad sensors. Limp mode was a "idiot light" not a delicate measure of engine operation. You should be able to detect the engine problems that limp mode protects you from.............

[tryan]

i thought 94's would just be the pro-tec ignition on a pcm? do you have a pro-boss or a gt-40?

[SGY]

Tyran

Jeez, Tyran you are a veritable encyclopedia of knowledge. Will you please move to Denver and take care of my boat. I need you man. We have a spare room and a mean four year old that we only let out of her cage to watch Fear Factor on Monday nights.

What do you think, all the ribs you can eat and O'douls you can drink. (Gave up beer for Lent. Maybe that's why I'm so cranky.)

Jaypoland, sorry to hijack the thread. But couldn't resist. If the above suggestions don't help, I'd call Vince at Skidim.com. He's seems to know almost as much as Tyran.

[tryan]

vince should know what the resistence of the temperature sensor should be according to the temp of the coolant. the coil packs fire 2 plugs each, so you might also have a crank position sensor issue, but i doubt it, since it runs fine to 3k. you can just run your fingers down the plug wires while the boats running, but that can get pretty interesting.

if the secondary can't open, the boat will feel like you are hitting a brick wall at about that rpm, so if the ignition checks out, you might inspect the secondary diaphram. it could just be stuck from resting alll winter. (vince has just the diaphram available if it's bad.)

[jaypoland]

No clue if I have a gt-40 or a pro boss, you lost me there. It's a pcm motor with the what I believe is the pro-tec ignition. Going back to the river next week and I'll try all that has been suggested. Need to figure it our or it will be a long week with no boat. I don't think its the temp sensor

[EchoLodge]

Problem Solved

Jay replaced the plug wires and boat runs sweet!

[skinautique]

Jaypoland,
If it is a 94, you have a carburated ford or a pro boss tbi
The GT-40 came out in the 1995 model year.