Engine stumbling, black smoke, when on rough trails or pitching side to side

[elripster]

Friends, I have an odd problem. My FJ60 normally purrs and runs quite well for an old 2F. It even passes smog here in CA with flying colors. This weekend I took it to Coyote Flats where it saw, for the first time, 10k'. On the way up, well before we reached 10k', it noticed it would bog down and lose power from time to time. I then tied it to hitting hard sections of the trail where the truck would get tossed around a lot. I thought it might be starving for fuel but the truck behind me noticed a lot of black smoke so it was running to rich. The, the problem would clear up and it would run just fine. This continued. I could start it just fine 10,500' and it would drive, albeit low on power, also just fine at that altitude, until I hit something that pitched the truck side to side and then the sputtering would return for 10-20 seconds and be fine again.

I am wondering if the float is sticking open? I basically have to find a trail to repeat the problem so it's a bit hard to make it come/go. One thing that did occur was the EGR pipe broke between the manifold and EGR valve, could that have caused it or be related to it?

Thanks!

Frank

 

[CruiserTrash]

Definitely running rich.

Wildcard, but do you know for sure your HAC works? You could absolutely pass smog in San Diego with an inop HAC because it doesn't do anything at sea level. As you go higher in elevation the oxygen per volume of air is less. The HAC compensates for that above 4000' by automatically opening. It then supplies extra air to the base of the carb. So you're going to be running rich at high altitude anyway, but if the HAC is stuck closed (from living life at sea level) you're going to be running even more rich.

Define "hitting hard sections" and "getting tossed around". If you're trying to rip through a boulder field at 10mph like you're driving a buggy the fuel in the bowl is definitely getting tossed around and could leave a temporary air gap where the jet is sucking - meaning you go from running rich to running 100% lean (i.e., no fuel). If you were crawling through a boulder field at 1mph and rocking back and forth, that would be less prone to happening. I do think checking the float level at idle on level ground is a good idea.

Stock 2F fuel pump? How old?

 

[elripster]

HAC is there but I have a DUI distributor so no timing advance. I can check to see if that system is still active. I have a stock 2F pump, maybe a year old, not many miles on it.

The truck doesn't have sway bars so it doesn't take much to get it rocking especially when the roof rack is loaded. I was going as slow as a H55F 4.56 geared 60 on 35's can go without stalling. However, I'd expect to maybe have a lean condition as you mentioned vs. the clearly rich condition that would then just go away and run fine. That's not to say it wasn't rich but it wasn't belching black smoke and sputtering rich which is what it was doing when the truck would rock side to side.

Frank