why is the exhaust so hot?

[teradymite]

Need some help diagnosing this problem:

Just bought an FJ60, fired the engine up, sounded good. As we check everything out (vaccuum leads, hoses, etc.), notice that the exhaust gas pressure is strong. Continue to play with things as the motor warms up. It revs up good, no noticeable hesitation, sounds strong. After about 15 minutes, my other buddy checks the exhaust and yelps as the gases burned all of the hair off the top of his hand. It was really hot. The exhaust manifold looked normal (was not glowing red), and the engine temperature was normal. Looking under the vehicle-also no glowing.

Our first thought was that the catalytic converter was bad. However, it has a thermosensor and no idiot light (or other signal) was going off. Also, I was told that if the cat was bad, I would not be able to rev the motor up. Any thoughts there?

Another mechanic suggested that I might be running lean. I live in Colorado at 9000 feet elevation. It should be running rich, if anything. Is there any way it could be running lean (faulty emissions equipment? there's lots of 'em)?

Final note, I bought it with no clutch (great price), So, It's sat at the previous owners for almost a year. It has not been out on the road and opened up-driven. I don't know if this could have any bearing . . .

Any insights would be really appreciated. Thanks,

 

[spencurai]

exhaust is supposed to be hot. the problem you might be looking at is it might be running really rich and the cat might be burning off a ton of HC and making the exhaust hot. this will be ok for a while but eventually the cat will fail due to heat break down. Do you have emissions in your area?

 

[teradymite]

Yeah, we have smog regs in the area. Of course exhaust is hot, I've just never had a situation where it would burn arm hair in about a second of exposure. The 'too rich' is another scenario that I had not considered. It makes more sense to me than 'too lean' (considering the thin air at high altitude). I'll look into that-thanks.

 

[xjc]

exaust temp is a function of how gas and oxigen burns, unless you are running alcohol or a turbo/super charger, your not gona have exhaust thats hotter than it should be!

exhaust is cooler when it comes out of your tail pipe when you are driveing than when you are idling. The exhaust pipe acts like a radiator and reduces the temp of the gas to some degree as it travels through the pipe. If you are driving, the air moving past the pipe cools better than if the car is still.

but then of course, Ive been wrong before

 

[spencurai]

Originally posted by xjc
exaust temp is a function of how gas and oxigen burns, unless you are running alcohol or a turbo/super charger, your not gona have exhaust thats hotter than it should be!

exhaust is cooler when it comes out of your tail pipe when you are driveing than when you are idling. The exhaust pipe acts like a radiator and reduces the temp of the gas to some degree as it travels through the pipe. If you are driving, the air moving past the pipe cools better than if the car is still.

but then of course, Ive been wrong before

yeah sometimes I think you over value that mechanical engineering degree......... just kidding bro


I would take it in to get emissions done on it. if they think everything is fine, I wouldn't worry about it. the almighty sniffer machine tells all!!

let us know what you figure out!

 

[xjc]

Originally posted by spencurai



yeah sometimes I think you over value that mechanical engineering degree......... just kidding bro

I know, I just wish I knew something more than that, the majority of what I know is theory and therefor useless

 

[Shawn]

How short is the pipe?

The longer, the cooler
The shorter, the hotter.

 

[teradymite]

Exhaust is stock length, running the entire length of an FJ60 wagon. Its a single tube with a single cat converter (unlike '88 and later-with 2 cats).

I guess, I'll check with the emissions people, look for obstructions in the tube/muffler, see if its running too rich, check the altitude compensation system, and check timing.

Thanks fellas,

 

[rustybronco]

"SPARKPLUGS"

They tell all: Tan = good
White = lean
Black = rich


Real scientific and you don't need no mechanic!

 

[Caleb]

Originally posted by rustybronco
"SPARKPLUGS"

They tell all: Tan = good
White = lean
Black = rich


Real scientific and you don't need no mechanic!

hats what I was thinking as I was reading this...check your plugs and also check the tail pipe...does it have an O2 sensor??? If so it could be bad and leaning the motor out...I say pull plugs first if they look fine then go get it emissioned and see what the report says...