Looking for help rough running (9 Viewers)

[shmukster]

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.

 

[Jdc1]

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.

Gary- did you check vacuum sources w/carb cleaner? Pinch Brake Booster line? Double check firing order and spark plug wire engagement?

 

[diesellibrarian]

I've had it happen where I've forgotten to reattach the engine ground after working on the engine and it ran like garbage until I realized my mistake. Cleaned the contacts and reconnected the ground wire and it went back to normal. Your ignition grounds through the distributor and engine, so a bad ground can definitely cause rough running, misfires, etc.

 

[Living in the Past]

Would check the hose from the PCV to the intake as well.

 

[Pighead]

When did you last adjust the valves? What is it timed at now? Can you get a manifold vacuum number?
Adding back the vacuum advance might help, I got a replacement single diaphragm vac advance module for my big cap from @4Cruisers. Carbon build-up on the pistons and valves might be a problem, do you have a bore scope? Try the Sea-Foam down the carb trick?

 

[numby]

Clogged fuel filter or leaky pump?

 

[brian]

What do heat gun numbers look like on the header tubes?....assuming it doesn't have a manifold.

 

[brian]

Put another dissy in it

 

[shmukster]

Tried a spare dissy I only have two!!!!

 

[brian]

Put another dissy in it

Tried a spare dissy I only have two!!!!

So far I'm 2/0 on failing to read the complete op.
Last idea....put a v8 in it.

 

[ceylonfj40nut]

how long has it been sitting without running? Check your carb is not gummed up with ethanol fuel crap. I would start with a valve adjustment, timing, vacuum reading when idling. If it aint idling, check your carb idle circuit and solenoid. Also see if fuel bowl level is right. OEM carb?

 

[65swb45]

Those compression numbers are actually a little low for a 60 engine. Add me to the chorus calling for a fresh valve adjustment.

 

[charliemeyer007]

A wall of text is too hard to read, Paragraphs are your friend and cost nothing.

Just cause you bought new parts doesn't mean they are good, whatever reason you swapped them in could still be valid - normally you would assume that symptom is caused by some other part and move on to figuring the next part. That's fine, but if you have checked everything and still got problems - then maybe one of the new parts are weak/bad.

I always start with scraping the aluminium contacts inside the cap - they build up a layer of aluminium oxide quickly which is an insulator. The little blade on my swiss army knife Tinker is my tool of choice.

A hair line crack in the cap is hard to see and will provide a shorting path. My old Delco Dizzy from 1980 was getting loose again. I worked on it way back in like 2005. It was starting to chew into the Brass contacts. I bought the chineasim delco of Amoron for $120. Moved my drive gear over to the new unit. I can't remember how long back the engine has run this good. My old cap and wires fit. I bought some Blue high $ wires back in 85 - they are still good. I like straight mechanical advance, rpms determine the timing no vac advance/retard crap.

I change my fuel filter out often. Water clogs the paper element and fuel can't pass easily. Leave them out in the sun for a few days and they are good as new. I put in a yellow bottle of fuel dryer like ounce a month - warm days and cool night will condense water right out of the air in your tank and the gas station.

I run the $10 electric diode fuel pump. They last about 10 years. I carry a spare. I have had issues with mechanical and other expensive electric pumps.

Looking for vac leaks by eye is weak. I use a can of WD 40 with a pee tube spraying lightly and quickly along the intake and carb gaskets on a cold idling engine - if the rpms kick up there is your leak. I have several hemostats sizes I can clamp off vac lines at will for easy testing.