Alaskan Rover
02-17-2011, 09:19 PM
I've got ghosts under the hood. I've been accused of having bats in the belfry, and as a Series IIA daily driver owner for 24 years, they may be right. But I have NEVER in 24 years had such a confounding party of mischevious ghosts under the hood!!
The problem is an ongoing but very intermittant cycle of misfiring:
The engine will be running smoothly...then all of the sudden and out of nowhere, it will begin misfiring...at least it seems like a misfire because I can tell it stuttering at the tailpipe...and then after 5 or ten minutes...the misfiring/stuttering will disappear JUST as mysteriously as it arrived, and will run smoothly again. I never know when it will do it. It is most common just after starting (but it's not a choke thing, either)...but it will just as likely do it when the engine is warm and has been driving for 40 minutes or more.
In trying to devine the problem....I've done the following:
1) Changed the distributer with new proline Rovers North distributer...thus new points and condensor and low tension lead came with it. Checked and adjusted point gap anyway.
2) New set of spark plug wires, including coil wire.
3) Replaced coil with unused spare.
4) Rebuilt the Rochester 1bbl carb (again)...checked float level and drop...but am having a hard time getting fuel/air mixture correct.
5) Timed engine to correct specs...using both static timing and induction timing.
6) Checked and adjusted all tappets for correct clearance.
7) As I write this am doing a Sea Foam treatment through the intake...stuff is now sitting for 30 minutes before starting. After that, I will put 3/4 pint of Sea Foam into crankcase (although I am apprehensive about this part...as my rover is a VERY high mileage rover...well over 450,000 miles!!...so am concerned about the SeaFoam eating away enough deposits near the seals that she'll leak even more than normal.)
I'm at my wits end trying to figure out these particular ghosts and banish them from under my bonnet!
Anybody have any ideas what this could be??
When I had the same symptons before, it turned out to be a faulty low-tension lead inside the distributer grounding against the distrib housing due to vibration. But now, the WHOLE distributer is new, including the low tension lead.
When it is in mis-fire mode...I take my timing light and check all spark plug wires and sure enough they're all firing as normal.
At the same time, when it's misfiring like that...I can remove the #4 plug wire and there is no difference...so it is something to do with the #4 cylinder...but what?
#4 compression is around 40 pounds. That's 40...not 140, BTW. When I add oil to that spark plug hole and then do another compression test, it rises to about 60.
Is it a risk doing the Sea Foam treatment (3/4 pint into crankcase oil) on the engine??
Does it sound like sticking valves (how the heck do valves 'stick' when they're pushed by pushrods, anyway??) or bad rings?
Add oil to the spark plug hole...if compression returns to normal = bad rings...need ring job.
If no change in comnpression, after adding oil to cylinder and compression still very low = bad valves.
But how about in my case....when the compression went up, but not all the way?
And if it was bad rings, it would smoke like hell (it doesn't smoke at all!) and it would not be intermittant.
But if it is bad valves, or sticking lifter, how can THAT be intermittant? Seems it would be ongoing.
The only good sign is that it doesn't smoke blue at all.
But the sympton presents as if it is an electrical (firing) problem. When it goes into mis-firing mode, you can tell easily back at the tailpipe.
HELP!!!!!
The problem is an ongoing but very intermittant cycle of misfiring:
The engine will be running smoothly...then all of the sudden and out of nowhere, it will begin misfiring...at least it seems like a misfire because I can tell it stuttering at the tailpipe...and then after 5 or ten minutes...the misfiring/stuttering will disappear JUST as mysteriously as it arrived, and will run smoothly again. I never know when it will do it. It is most common just after starting (but it's not a choke thing, either)...but it will just as likely do it when the engine is warm and has been driving for 40 minutes or more.
In trying to devine the problem....I've done the following:
1) Changed the distributer with new proline Rovers North distributer...thus new points and condensor and low tension lead came with it. Checked and adjusted point gap anyway.
2) New set of spark plug wires, including coil wire.
3) Replaced coil with unused spare.
4) Rebuilt the Rochester 1bbl carb (again)...checked float level and drop...but am having a hard time getting fuel/air mixture correct.
5) Timed engine to correct specs...using both static timing and induction timing.
6) Checked and adjusted all tappets for correct clearance.
7) As I write this am doing a Sea Foam treatment through the intake...stuff is now sitting for 30 minutes before starting. After that, I will put 3/4 pint of Sea Foam into crankcase (although I am apprehensive about this part...as my rover is a VERY high mileage rover...well over 450,000 miles!!...so am concerned about the SeaFoam eating away enough deposits near the seals that she'll leak even more than normal.)
I'm at my wits end trying to figure out these particular ghosts and banish them from under my bonnet!
Anybody have any ideas what this could be??
When I had the same symptons before, it turned out to be a faulty low-tension lead inside the distributer grounding against the distrib housing due to vibration. But now, the WHOLE distributer is new, including the low tension lead.
When it is in mis-fire mode...I take my timing light and check all spark plug wires and sure enough they're all firing as normal.
At the same time, when it's misfiring like that...I can remove the #4 plug wire and there is no difference...so it is something to do with the #4 cylinder...but what?
#4 compression is around 40 pounds. That's 40...not 140, BTW. When I add oil to that spark plug hole and then do another compression test, it rises to about 60.
Is it a risk doing the Sea Foam treatment (3/4 pint into crankcase oil) on the engine??
Does it sound like sticking valves (how the heck do valves 'stick' when they're pushed by pushrods, anyway??) or bad rings?
Add oil to the spark plug hole...if compression returns to normal = bad rings...need ring job.
If no change in comnpression, after adding oil to cylinder and compression still very low = bad valves.
But how about in my case....when the compression went up, but not all the way?
And if it was bad rings, it would smoke like hell (it doesn't smoke at all!) and it would not be intermittant.
But if it is bad valves, or sticking lifter, how can THAT be intermittant? Seems it would be ongoing.
The only good sign is that it doesn't smoke blue at all.
But the sympton presents as if it is an electrical (firing) problem. When it goes into mis-firing mode, you can tell easily back at the tailpipe.
HELP!!!!!