I'm frustrated with the way the engine in my 40 is running. It started a few months back, it wasn't idling quite right, left a friend drive it at a recent offroad event and it progressively got worse. Frankly I was embarrassed at the way it ran for him. I drove it home without a lot of trouble, but it is at the point now where I wouldn't drive it on the road. Here's the skinny............
It's my 76 FJ40, the engine is from an 87 FJ60 and is a Jim C performance rebuild done about sixteen years ago. Ran great for all these years. Stock carburetor rebuilt by Jim and stock intake, has Manafre headers, and the stock fat body electronic distributor. Diaphragms have been bad in the distributor for years so no vac advance. Compression numbers are all high 120-high 130 and that's tested dry so that looks good to me. The spark plugs looked decent when I started to look at this issue but I replaced them anyway with brand new Toyota plugs. Distributor cap and rotor have been changed all these parts are OEM Toyota.. Has brand new Denso ignition wires. When idling or driving it sounds like there is a misfire- you can hear it in the exhaust and feel it.
When I remove the spark plug wires one at a time with the engine idling, idle drops significantly when numbers 1 and 6 are pulled, hardly at all with numbers 2, 3, and 4, and slightly with #5. When I happened to look down into the engine bay when it was running rough I noticed that through the large diameter vent hole in the cap I could see sparks jumping around. Thought that was it, pulled the distributor and replaced with another stock distributor. Still the same problem and I must say while replacing the distributor I had removed the valve cover and all looks well with the rocker assembly I didn't see anything amiss in there. I've looked at all the vacuum sources and don't seem to have anything open there, and I did put a socket on the manifold bolts and nuts but they're all tight. I've even changed the carburetor to another, and the problem persists. Frankly I don't believe it's a fuel issue but who knows?
Would be interested in hearing some opinions and hopefully have someone steer me in the right direction. I've owned this truck for fifteen years, have owned the engine even longer (it was in my orange and white 55 when I flopped it), and have never before had a performance issue.
It's my 76 FJ40, the engine is from an 87 FJ60 and is a Jim C performance rebuild done about sixteen years ago. Ran great for all these years. Stock carburetor rebuilt by Jim and stock intake, has Manafre headers, and the stock fat body electronic distributor. Diaphragms have been bad in the distributor for years so no vac advance. Compression numbers are all high 120-high 130 and that's tested dry so that looks good to me. The spark plugs looked decent when I started to look at this issue but I replaced them anyway with brand new Toyota plugs. Distributor cap and rotor have been changed all these parts are OEM Toyota.. Has brand new Denso ignition wires. When idling or driving it sounds like there is a misfire- you can hear it in the exhaust and feel it.
When I remove the spark plug wires one at a time with the engine idling, idle drops significantly when numbers 1 and 6 are pulled, hardly at all with numbers 2, 3, and 4, and slightly with #5. When I happened to look down into the engine bay when it was running rough I noticed that through the large diameter vent hole in the cap I could see sparks jumping around. Thought that was it, pulled the distributor and replaced with another stock distributor. Still the same problem and I must say while replacing the distributor I had removed the valve cover and all looks well with the rocker assembly I didn't see anything amiss in there. I've looked at all the vacuum sources and don't seem to have anything open there, and I did put a socket on the manifold bolts and nuts but they're all tight. I've even changed the carburetor to another, and the problem persists. Frankly I don't believe it's a fuel issue but who knows?
Would be interested in hearing some opinions and hopefully have someone steer me in the right direction. I've owned this truck for fifteen years, have owned the engine even longer (it was in my orange and white 55 when I flopped it), and have never before had a performance issue.
