Intermittent ignition problem

[gregskjei]

I have a 2000 4.3 with a thunderbolt V ignition.
It starts and runs fine, but after about 5 minutes at operating speed it starts to miss.
This problem sometimes goes away as I run the boat more or sometimes gets worse. It also gets better below 3,000 rpm.
I have set the base timing, changed plugs, rotor, cap and coil to no avail.
When I put a timing light on it, I can see the timing jumping advance as it misses.
The ignition module and sensor seem to be all that is left to change.
P.S. I spent 3 months running the gamut on fuel issues - fuel filter, water, anti-syphon valve, etc., and am convinced that the problem is ignition.
Thanks for any help. I have had a whole season of frustration attempting to deal with this problem.

 

[DutchMerc]

Re: Intermittent ignition problem

I've been there, done that , tried everything, and at the end i had to change the ignition module. I know it is an expensive part, but i think you have no other option....You can verify that the module is the problem bij changing the pilot leads and plug-cables to the other coil, and you can see that now the other one is missing some parks...Good luck.

 

[Haut Medoc]

Re: Intermittent ignition problem

I have a 2000 4.3 with a thunderbolt V ignition.
It starts and runs fine, but after about 5 minutes at operating speed it starts to miss.
This problem sometimes goes away as I run the boat more or sometimes gets worse. It also gets better below 3,000 rpm.
I have set the base timing, changed plugs, rotor, cap and coil to no avail.
When I put a timing light on it, I can see the timing jumping advance as it misses.
The ignition module and sensor seem to be all that is left to change.
P.S. I spent 3 months running the gamut on fuel issues - fuel filter, water, anti-syphon valve, etc., and am convinced that the problem is ignition.
Thanks for any help. I have had a whole season of frustration attempting to deal with this problem.

I don't see ignition new wires on the list.....
Old wires can & do have crossfire, even if they look OK, especially when things get warm....
New wires would also be part of a full tune up, change them & move on to other causes if the condition persists.......
There are specific tests for the module & sensor, before you waste money on new ones......

 

[gregskjei]

Re: Intermittent ignition problem

You're right about the wires. When I bought the boat this spring the previous owner had already done a complete tune-up including wires. Unless they were faulty new they really should be OK. I could spend this money first, but was assuming that faulty wires wouldn't cause the timing jumps that I am seeing?
Thanks