Fellow mudders, hoping to get some help. I’ve searched for results on this, but didn’t find anything that matched my situation.
Here’s my situation
2/75 Fj40 with 80k original miles (afaik)
Had been running ok, but recently developed a ‘miss’ that is worst at higher loads (climbing hills) and the idle has gotten rougher.
I checked/adjusted valves, nothing seemed too far off.
I went through the dizzy- check spark, new cap/rotor/wires/plugs. checked the mechanical advance, which seems slow to return - not sure if that is contributing to my issue?
Carb seems ok, a little on the rich side, but I would expect all plugs to foul equally if it was a carb issue.
Ran compression test numbers looked ok/good to me; cylinders 1-6 were 145,141,145,144,141,145. 2 and 5 were the lowest, but not crazy low.
Checked vacuum at brake booster. Vacuum looked good at 18, steady at idle with maybe a slight ‘tick’. Seemed inconclusive, other than to rule out intake manifold leaks, but I’m a newbie so ?
Put in new plugs, and plugs 2 and 5 fouled pretty quickly after a few mins at idle. Plugs 3 and 4 were dark, but not shiny with oil, and plugs 1 and 6 were perfectly clean.
Ran leak down test - somewhat arbitrarily chose 80psi as the pressure. Not sure if I should sneak up on it with the regulator on not?
#2 showed 66 psi and #5 showed 63 when 80psi was put on the cylinder, the rest we’re closer to 70. The majority of the leakage was coming out the head (it was loud out the bulkhead fitting where the head cover vent is routed to the carb) no noticeable leakage out the carb or the exhaust.
I’m thinking it’s valve guides/seals, but I’m hoping for a second opinion from the wealth of knowledge on this site.
Also, if I’m right, is it feasible to ‘just’ replace the valve seals with the head on, or should I take the head to a shop to have them go through it fully?
Any other ‘lower cost options? I’m running 10w/40 Dino oil, maybe go to 20w/50?
I’m running NGKBPR4EY plugs, maybe go a step hotter?
Thanks gents.
First pic is a brand new plug in #2 after a few mins of idle.
Second is of #5 and my setup
Here’s my situation
2/75 Fj40 with 80k original miles (afaik)
Had been running ok, but recently developed a ‘miss’ that is worst at higher loads (climbing hills) and the idle has gotten rougher.
I checked/adjusted valves, nothing seemed too far off.
I went through the dizzy- check spark, new cap/rotor/wires/plugs. checked the mechanical advance, which seems slow to return - not sure if that is contributing to my issue?
Carb seems ok, a little on the rich side, but I would expect all plugs to foul equally if it was a carb issue.
Ran compression test numbers looked ok/good to me; cylinders 1-6 were 145,141,145,144,141,145. 2 and 5 were the lowest, but not crazy low.
Checked vacuum at brake booster. Vacuum looked good at 18, steady at idle with maybe a slight ‘tick’. Seemed inconclusive, other than to rule out intake manifold leaks, but I’m a newbie so ?
Put in new plugs, and plugs 2 and 5 fouled pretty quickly after a few mins at idle. Plugs 3 and 4 were dark, but not shiny with oil, and plugs 1 and 6 were perfectly clean.
Ran leak down test - somewhat arbitrarily chose 80psi as the pressure. Not sure if I should sneak up on it with the regulator on not?
#2 showed 66 psi and #5 showed 63 when 80psi was put on the cylinder, the rest we’re closer to 70. The majority of the leakage was coming out the head (it was loud out the bulkhead fitting where the head cover vent is routed to the carb) no noticeable leakage out the carb or the exhaust.
I’m thinking it’s valve guides/seals, but I’m hoping for a second opinion from the wealth of knowledge on this site.
Also, if I’m right, is it feasible to ‘just’ replace the valve seals with the head on, or should I take the head to a shop to have them go through it fully?
Any other ‘lower cost options? I’m running 10w/40 Dino oil, maybe go to 20w/50?
I’m running NGKBPR4EY plugs, maybe go a step hotter?
Thanks gents.
First pic is a brand new plug in #2 after a few mins of idle.
Second is of #5 and my setup