I'll be driving through town on a 90* day and my temp gauge will peg up to the A in NORMAL and if I stop at a stop sign, my RPMs drop down to ~400 and the truck begins to violently shake. Holding down the gas to increase RPMs helps to restabilize it. However, as soon as I get on the freeway, the temp gauge goes down to about O (which to my knowledge is normal and good). Why is it heating up so fast? It will get that hot just by driving to the other side of town (about 15 minutes) and I can watch the temp gauge rise as I sit at a stop light or in traffic (again, normal). How can I fix this? It can go from the O to the M-A range in NORMAL even while sitting in the Mc.donalds drive through.

Also I have one other oddity here. The last time I put in gas, I removed gas cap and a bunch of pressurized hot air came bursting out of the gas tank. I assume these were fuel vapors...why were they built up like that? Is it a problem?

I dont think I have the evaporative emissions crap on my gas tank because I don't have a charcoal canister under the hood anywhere if that helps at all...

 

have you tried flushing the coolant and putting fresh fluid in?

 

do you have a fan shroud? are you running a solid fan or fan clutch?

 

Isn't the charcoal canister sometimes mounted on the right frame rail under the cab??

Factory gauges are notoriously inaccurate. I recommend installing a set of gauges or at least a coolant temp gauge for better info than "N-O-R-M-A-L".

Lastly, the stumbling could be caused by a mild case of vapor lock. Try insulating the fuel line with a split rubber hose to see if it makes a difference. That or the float is set a hair too high.

 

It has brand new green coolant in it that's about a month old at best. It has a fan clutch and a fan shroud. The shroud is in good condition and the fan clutch appears to be in working order.

As far as the vapor lock goes, what is causing this and better yet how can I get rid of it? I don't have a charcoal canister or lines for one.

 

You have a shroud and fresh coolant and you heat up at idle. I would try turning your idle up a little. If that doesn't work I would try a cooler thermostat. These are the two easy fixes. after that it is time to have the radiator checked out for blockage.
You say it runs rough at idle but fine just off idle? Sounds like one or maybe both idle mixture screws are blocked. It is very simple to fix. Turn your screws in gently until they bottom out while counting the turns. Remember how many turns it takes each one to bottom out. Then remove them and blow some compressed air down the holes to clear them. Then replace the mixture screws, bottoming them out then backing them off the same number of turns that it took to bottom them out the first time.
If you don't have access to an air compressor that Air In A Can stuff that is used to blow keyboards and computer parts works well. Use the straw that comes with it.
Start it up and see how it idles.
To reset the mixture screws, warm the motor up. If it idles smoothly turn one screw in until the motor starts to stumble a bit. Back it out until it smooths out. Then I will back it out another 1/4 of a turn, that's it. Repeat with the other screw and you are ready to run.
Most recently I had to replace the rubber fuel line and move my inline filter up close to the carb so that the majority of the rubber was before the filter. The Ethanol in the gas eats the rubber and I was getting chunks of it in my idle mixture screws.
You may have to do the same if this becomes a recurrent problem.

 

If your vent system is removed and blocked off you will need a vented gas cap.

 

Those aren't fixes, they're band-aids.


A few things:

1. Is this a new problem? Have you driven the truck in similar weather without this happening?
2. Fan clutch appears to be in working order. Have you actually checked it?
3. Don't even bother referencing the factory gauge; it's almost completely useless. Like HIO said, get a cheap aftermarket gauge to verify.

It's possible that your truck is running hot, heating up the fuel in the fuel lines, vapor locking, and causing your truck to stumble at idle. Get the temperature problem fixed and see if that doesn't solve the idle problem.

 

How do I check to see if the clutch works? All I know is that the fan moves when the engine is running.

This problem is an interesting one, Once the weather warmed up around here, I began experiencing issues with the truck dying while driving and not restarting for several hours. I also had issues with hard starts when hot and misfires at random times. That led us to replace the following parts:

Fuel pump
fuel pump eccentric
ignition module
distributor
coil
spark plugs
coolant
choke (manual replaced with electric)


Since replacing these parts, the truck does not stall. It just starts acting like its out of gas (bucking, missfiring, dropping rpms, etc.) Putting your foot in it clears it up and it runs ok. Now it still has that random miss at any rpm level, it bogs horribly (think timing too retarded...by alot for comparisson) when hot, blows tons of white smoke on start up, and still has fuel boiling and is still hard to start (acts like its out of gas) when hot. And to top it all off, it can go from being fully cold to almost overheating just by driving through town and stopping at stop lights...could my radiator messed up? My dad thinks its plugged...

 

Now it sounds like vapor lock in the fuel lines. As mentioned before, insulate your fuel lines from the engine heat.

 

How do you figure?
If the idle rpms are down from normal the motor will tend to overheat during stop and go driving in hot weather since it will not pull as much air through the radiator.
A cooler thermostat will delay overheating and a faulty thermostat may well be the problem.
I have learned the hard way to check for the simple solution first.

 

I'll insulate the lines tomorrow after work. What's up with the high heat levels? Is it the radiator?

 

A clutch fan will spin some whether or not it's actually functioning.

With the engine cold (having sat overnight) and off, spin the fan; should be pretty easy to turn. Now start the truck and observe the fan. It should spin faster, blow more air, and produce more noise as the engine heats up. Once the engine's up to operating temp, shut it down. Try to spin the fan again; it should be noticeably harder to spin. If there isn't much change from cold to hot, your clutch needs replacing.

Get your timing set properly. Retarded timing can make an engine run warm.

 

And also slow your idle, compounding your problem.

 

I was just assuming the idle was set properly in the first place. Of course, if the idle was set too low before this all started, it could certainly be the problem.

A cooler thermostat will do just that: delay overheating. If the factory thermostat isn't keeping the engine cool, there is an underlying problem.

A bad thermostat would result either in overheating all the time (stuck closed), overheating on the highway (stuck partially closed), or underheating (stuck open).