Hesitation while driving at constant speed?? 88 d50

[BradMph]

correct, should be some springiness in it and like Camoit said just a few degrees turn.

Are you sure your getting hesitation also. Maybe that's the way the truck just runs like and your sensitive to it? The smog device stuff could be increasing the hesitation, Andy's idea sounds like a good fix if you can leave it removed and block all the smog ports without emissions test looking under your hood it might be a good idea later on trying.
when the truck is running stroll back to exhaust pipe and if the exhaust burns your eyes within a second or two your rich, too rich. If its just heat, should be ok. Don't breath the crap, just do a quick little eye test. You get worse exposure daily just breathing our polluted air. It's not the normal way to check mixture, but it can give you a quick answer.

[cnatsu1]

Had some time to play with the truck today and found a little nick in one of my vacuum lines. Thought I'd checked them all, but this was down at the bottom of the mikuni carb with two other lines. Amazing how many vacuum lines there are on this thing. Fixed my original stumble problem - YEAH!! Still on my first tank of gas, so I want to make sure any old gas is out of the system before saying for sure. Going to check my plugs and timing next and want to check out the advance as someone else mentioned.

New question: truck doesn't want to start now when it's warm. When I pulled my air cleaner off I could hear some bubbling (truck was hot and had just been driven) and there was a little smoke coming up from the choke side of the carb. Looked like a little witches caldron. I'm pretty sure this isn't normal. Any ideas what this could be? I was about to order a weber carb, but now I've fixed the stumble problem, I'd really like to hold off on that expense for now, especially with having to get the electric fuel pump to go along with it.

[camoit]

It sounds like the thermostat is not working or somthing along them lines. That was the sound of boiling water. Fix that before going any further, do not over heat the thing or you may need a head. If you don't have a fan shroud get one. Use a Montero one. There metal and easy to find at the recycle places. Any fan more then 2 inches away from a radiator must have a shroud. Not enough air to cool it at idle. This is just one of many Mitsubishi's mistakes.

[BradMph]

Number one idea, Listen to what Camoit said and do not over heat these trucks. They are notorious for cracking the heads and do it with a slight over heating. Watch the temp gauge, if there is not one, Get one. I run a 180 degree thermostat. Lets them run cooler and gives a little extra time if you see a rise in heat out of the ordinary. Flush out radiator when replacing a thermostat.
I cringe when someone says their truck is over heating and didn't pull over immediately or seen fumes from heat off engine cause it reminds me of my over heating experience. I watch gauges and still couldn't catch it in time, next thing I know, I am making milkshakes in my oil.

[cnatsu1]

I don't think it was water. I was thinking more along the lines that gas was going in the top of the carb (where it probably shouldn't be going) and burning off from the engine heat. The steam/smoke was coming from inside the carb and I couldn't see or hear anything until I removed the air filter. My temp gauge isn't working, but it didn't seem like the engine was overly hot. I'll put the temp gauge and thermostat at the top of my list though and look for a shroud.

In my Haynes diagram it looks like the enrichment jet is on that side of the carb. Maybe it's leaking down into the top of the carb without going down the intake after I shut it off??

[Andy 2]

The wisp of vapor coming from the carb is normal I think. Just hot air/fuel mixture evaporating from the motor. The bubbling sound could be the overflow from the cooling system. Once you turn off a hot engine the coolant stops circulating and cooling system pressure rises as the heat from the head is absorbed by the coolant. Your rad cap will let pressure in excess of 13 psi escape into the overflow bottle and then the coolant will be drawn back in by the vacuum created as the engine cools. If the rad cap is old it my not be holding enough pressure to stop the coolant from boiling. The bubbling could be the coolant boiling in the cylinder head. Make sure your rad is full when the engine is cold and the coolant is up to the full line on the overflow bottle. Check the overflow hose for cracks and leaks and replace it if defective or the coolant might not get sucked back into the radiator. Also might want to check the coolant with a hydrometer to make sure the water content is not too high. Water boils at a lower temperature than anti-freeze. What does the temp gauge say when you are driving? Both of mine run at just under half way to the hot line while moving down the highway and around halfway or just a bit better in city driving.
Hot starts have always been an issue with my Mikuni carbs also. I find that if I crank it over then wait a few seconds then crank it again, it starts on the second crank. Only in the summer. Sometimes depressing the accelerator just a bit while starting helps too.

[cnatsu1]

checked my advance - working (put a spare tube on and sucked on it to see it move), timing was off - set to 8btdc, fixed broken thermostat wire, plugs were BLACK. Cleaned plugs and set gap. No more witches caldron in the carb and the truck seems to be starting good while warm now. Going to get a compression tester and check compression.

[BradMph]

These trucks always seem to burn rich with all the smog stuff on them. At least mine use to, had blacken plugs around ring and tannish looking electrode. Just as long as it is not wet with fuel, oil or water.

[pennyman1]

Tan electrode is what you want to see on these trucks, the outer ring doesn't really matter unless it is really cruddy black or some other color.

[camoit]

An engine that is on the verge of overheating or just lightly overheating will make that sound in the intake and head. If it's blowing into the overflow bottle it would come from up front. Ikeepitclean's truck was making that noise just after break in because it had no shroud. Even though the gage showed half way up. But how hot is H or cold is C?

[Andy 2]

I believe the ideal operating temp. is 190-195 degrees F. so I would think the middle of the gauge would indicate around there. You could try a 180 degree thermostat for the summer but a fan shroud would be a better fix as Camoit says.