78 2f highway speed chug/cough - possible water in fuel

[TimeIsMoney]

Did you happen to check spark plugs? Reason I asked is I thought I was having some fuel related issues at speed. I did find a bit of debris in my idle jet and seemed to get better. Pulled a couple plugs just to check and had some white ashy (extra oil burnoff) from what I read. Anyway I cleaned all the plugs and re-gapped and it was like a new vehicle. Just something to try.

 

[jbjasp]

Update:

Purchased some HEET from the gas station after another 50 miles or so. Didn't change the chugging/sputtering at high speeds. Continued to get worse throughout the day, but I did end up making it through the blizzard to Spokane. Cruiser still got me home in one piece!

Hills were rough, only about 20mph max in 3rd, and lots of sputtering. I checked air filter, but really do think it has something to do with the fuel filter because it wasn't ever at a consistent speed or RPM, but more of a certain "umph" level. This makes me think it'sView attachment 1608946 related to the amount of fuel entering the system.

Refilled with premium in Coeur d'Alene (less ethanol) and added an injector cleaner. Was noticeably better for the last 30 miles into Spokane, but would sputter lightly past about 50. Luckily traffic was only moving about 40 anyways because of the snow, so I wasn't holding up too many more people in the right lane

Will change fuel filter tomorrow and update with results.

Lschumm, have you had any success with your issue yet? I have the same problem with my 1983 FJ43 and the issue sounds identical. I was driving mine halfway across the country after purchasing it, and I t ran perfectly at highway speeds for the first 500 miles. My issue also started when I left the gas cap off and it was drizzly weather outside. I didn’t know I left the cap off and it was running like a top until the next fuel stop. When I pulled out of the gas station after a fill it died like it ran out of gas. The initial onset was at low speeds. We added Sea Foam, and drained the gas tank. We could get it up to 50 and it would lose power/fuel pressure like it was choking so we towed it back to TX. After returning home, I changed the fuel filter and replaced the fuel pump with OEM, cleaned the spark plugs, and blew out the fuel line. It started running fine after that at low speeds. When I get it on the highway now, the sputtering starts at 50-55 mph. I slow down and it takes it a few minutes to recompose and then it’s fine again at lower speeds. It does not seem like it’s an RPM trigger but a MPH trigger when it occurs, which is illogical to me. I can hit the same RPM in 3rd gear as when the issue occurs in 4th @ 50 mph, and it does not sputter in 3rd. The next thing is to rebuild the carb and to pull the gas tank and clean it. Just wondering if you’ve sorted your issue out and have any new insight since they sound very similar. Thanks!

 

[Lschumm]

Lschumm, have you had any success with your issue yet? I have the same problem with my 1983 FJ43 and the issue sounds identical. I was driving mine halfway across the country after purchasing it, and I t ran perfectly at highway speeds for the first 500 miles. My issue also started when I left the gas cap off and it was drizzly weather outside. I didn’t know I left the cap off and it was running like a top until the next fuel stop. When I pulled out of the gas station after a fill it died like it ran out of gas. The initial onset was at low speeds. We added Sea Foam, and drained the gas tank. We could get it up to 50 and it would lose power/fuel pressure like it was choking so we towed it back to TX. After returning home, I changed the fuel filter and replaced the fuel pump with OEM, cleaned the spark plugs, and blew out the fuel line. It started running fine after that at low speeds. When I get it on the highway now, the sputtering starts at 50-55 mph. I slow down and it takes it a few minutes to recompose and then it’s fine again at lower speeds. It does not seem like it’s an RPM trigger but a MPH trigger when it occurs, which is illogical to me. I can hit the same RPM in 3rd gear as when the issue occurs in 4th @ 50 mph, and it does not sputter in 3rd. The next thing is to rebuild the carb and to pull the gas tank and clean it. Just wondering if you’ve sorted your issue out and have any new insight since they sound very similar. Thanks!

Update #2: Purchased a new fuel filter and replaced it with no change. Still ran perfect around town, but trying to accelerate to highway speeds wasn't easy. Wouldn't do more than about 50-55 without the sputtering. I took TapRackNGo's advice and purchased some new spark plugs (I hadn't changed them in the 3 years I've had the cruiser, its anyone's guess how long it had been). There was definitely some gunk on the plugs, I can upload some pictures of them when I get home. This solved the issue! Happily ran 60 on the way back home...

However, the cruiser developed the issue again about 2 weeks later. I am wondering if its now more spark system related. I ordered new points and a condenser and will re-clean the plugs and install them when I have some free time . Definitely sounds like a similar issue, being speed related and not RPM. Let me know if you find figure out anything else!

 

[JSharp]

Any updates on what finally was the issue? My 77' started this for the first time this am. Exact same issues, chugg/ cough in 4th gear above 50 mph. Runs fine in town. Feels like fuel or spark issues?

 

[Lschumm]

Yes! It ended up needing a carb cleaning, mechanic said it was half clogged. Also replaced the fuel filter closest to the gas tank, there was some rust pieces in mine which likely came from inside the tank. Not sure which was the bigger issue but with both cleaned/replaced it runs great now with no chug. Drove 1,100 miles back to Denver. Now to fix the rust...

 

[JSharp]

Yes! It ended up needing a carb cleaning, mechanic said it was half clogged. Also replaced the fuel filter closest to the gas tank, there was some rust pieces in mine which likely came from inside the tank. Not sure which was the bigger issue but with both cleaned/replaced it runs great now with no chug. Drove 1,100 miles back to Denver. Now to fix the rust...

Good to know. I figured it was either carb or spark issue. My guess is my carb needs a cleaning.

Thanks for replying so quickly!

 

[tls3601]

78 did not have a vented gas cap. The emissions system is suppose to keep gas fumes from escaping. A vented gas cap would allow fumes to escape.

Yes John is correct, non vented cap on my ‘10/78.

 

[Ol'40]

Check your fuel filter too. Might be restricting flow and starving the engine at high speeds.

I had simular issues, engine randomly cutting out, i thought of all the problems, carby, fuel pump etc . Started looking at the easiest bit, the fuel filter, low and behold, full of rust particles.. $5.00 later we're on the road again..