Help Chasing Erratic Idle Please
#91
Registered
Thread Starter
Thanks again for sticking with me on this all!
Late last year I checked base timing which for some reason seems was grossly out of adjustment as detailed in the above post.
Why would such a large adjustment be necessary if the hold down bolt was incredibly tight?
Nonetheless, the boat ran good on the water but still had one instance of off idle rpm surge; however, the usual stall on hose at the ramp (hot engine) while trying to flush was prevalent. As usual the rpm's had to be brought up to 1200 for it to run on hose. As a reminder if I shut the boat off on the water and restart I've NEVER had the issue I do on the hose when hot.
At a complete loss other than checking compression; however, my vacuum reading (lowest 15 hg) doesn't demonstrate weak compression.
Keith
Late last year I checked base timing which for some reason seems was grossly out of adjustment as detailed in the above post.
Why would such a large adjustment be necessary if the hold down bolt was incredibly tight?
Nonetheless, the boat ran good on the water but still had one instance of off idle rpm surge; however, the usual stall on hose at the ramp (hot engine) while trying to flush was prevalent. As usual the rpm's had to be brought up to 1200 for it to run on hose. As a reminder if I shut the boat off on the water and restart I've NEVER had the issue I do on the hose when hot.
At a complete loss other than checking compression; however, my vacuum reading (lowest 15 hg) doesn't demonstrate weak compression.
Keith
#92
Registered
When you checked timing was the motor placed in base timing mode?
#94
Registered
With my pea brain it has to be vacuum leak because
If vac line is removed, fuel pressure increases
IAC is trying to idle but is not rich enough but is when cold
If vac line is removed, fuel pressure increases
IAC is trying to idle but is not rich enough but is when cold
#95
Platinum Member
Platinum Member
See post #2......
#96
Registered
Thread Starter
I've searched for leaks all up around the plenum and intake mani areas. Nothing can be heard and carb cleaner spraying in said areas netted nothing but paint removal.
#97
Registered
Would I not be seeing a drop in vac gauge pressure between hot and cold or less than spec? I do not.
I've searched for leaks all up around the plenum and intake mani areas. Nothing can be heard and carb cleaner spraying in said areas netted nothing but paint removal.
#98
Registered
You can check for internal vac leak by plugging all the holes in the valve covers except 1 where you press down with with the palm of your hand to seal the last hole with eng idling (cold eng is waay more comfortable). If you can feel that suction is building on your palm, you have a internal vac leak like suggested above.
On a side note: I once "upgraded" all the intake manifold bolts on a SBC car eng. Didn't realize the new ones were slightly longer. They would tighten down just enough to start compressing the gaskets then bottom out. Replaced the gaskets twice before I figured out what was going on. It had a internal vac leak.
Anyway, its a quick and easy thing to check for.
What's was the deal with the stripped intake plenum bolts mentioned on post #90? Could that be a potential vac leak??
On a side note: I once "upgraded" all the intake manifold bolts on a SBC car eng. Didn't realize the new ones were slightly longer. They would tighten down just enough to start compressing the gaskets then bottom out. Replaced the gaskets twice before I figured out what was going on. It had a internal vac leak.
Anyway, its a quick and easy thing to check for.
What's was the deal with the stripped intake plenum bolts mentioned on post #90? Could that be a potential vac leak??