Hesitation/Jerking after the FJ 55 warms up

1,149 Views | 9 Replies | Last: 4 yr ago by 1agswitchin4lanes
MR Gadsden
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I recently bought a 1978 FJ55 and had it shipped from Nova Scotia to Midland. Everything on it is original and it has the 2f straight six and has been de-smogged so no EGR valve or anything. It fires up right away and idles well. it runs down the road great for about 15 minutes. Then it starts to act up. If im at higher speeds, like 80-90km an hour (55mph ish) and I need to accelerate or say step on the gas to go up an incline the truck jerks and stutters. If I slow down to a stop and run through the gears again it seems fine until I get back into 3 and 4th gear. And this only happens when the truck gets warm (not overly hot) and it's hot outside. I haven't had it do this when I run it in the evening, but im about to take it out on 307 and run it toward Stanton and see if it acts up at night.

I was thinking maybe a vacuum issue or power valve but hoping someone else has seen this issue before. I'll try and get a video of it running both good and bad.

Any thoughts?
MR Gadsden
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I ran the truck for about 40 minutes last night and it never acted up. So it's just when it is 95+ degrees it seems. I don't think this truck has ever been driven in that kind of temperature.
reddog90
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AG
Vapor lock? Old fuel filter?
Jrod05
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AG
Fuel filter is my bet.
MR Gadsden
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I was doing some research and I think I'm leaning toward vapor lock. I found that because it's a Canadian FJ it doesn't have the carb cooling fan and this could be contributing to the problem in the heat.

https://forum.ih8mud.com/threads/fj40-carb-cooling-fan-do-you-run-yours.401196/

So, I'm going to look at some after market solutions for the quick fix and then try and track down the actual original parts.
DeWrecking Crew
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Along those same lines...don't they have different recommended jets for elevation? Did this one live its life in higher elevation?
MR Gadsden
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It was in Nova Scotia so pretty much sea level. Not sure the elevation in Midland makes that much of a difference, but that was something I was looking into.
lawless89
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Bruh....pics??
MR Gadsden
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My bad. I had pics on the Landcruiser thread. Forgot Rule #1 on this one.



Fan should be on the right side of the engine in this pic.



MR Gadsden
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notice the -46 degree's Celsius Oct 91 on the fan cowling. There's another one for -43 degrees in 93 in front of the radiator. I was tempted to write +114 degrees Aug '19 somewhere.
1agswitchin4lanes
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AG
I have this same issue with my 78FJ40 as well. Wired up the fan for the carb and does just fine.
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