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250rdakota
Dodge Dakota
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9/16/2004
19:57:19
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 Subject: exhaust manifold heat control valve???
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Has any one heard of this and what does it do??? Its on the driver side of the engine and it goes right through the manifold pipe. Its round and has a coiled spring on it. My spring is broke what will the effects of this being broke be???
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250rdakota
Dodge Dakota
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9/16/2004
19:58:31
| RE: exhaust manifold heat control valve???
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oh ya its a 1987 with a 3.9 in it
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if
Dodge Dakota
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9/16/2004
20:48:14
| RE: exhaust manifold heat control valve???
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if it bothers u just swap out the manifolds for headers, cheap fix
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Bob Lincoln
Dodge Dakota
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9/16/2004
21:10:55
| RE: exhaust manifold heat control valve???
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It is a flapper valve in the exhaust manifold, connected to a bimetallic coil spring. Its purpose is to divert hot exhaust gas through a passage in the intake manifold ("crossover passage") to heat up the engine faster, vaporize the air/fuel mixture better while the engine is cold. It improves cold driveability. When hot, the coil spring loses tension and the counterweight rotates the flapper so that the exhaust gas goes straight out and does not apply heat to the manifold.
The technology is over 40 years old. The shaft on the flapper used to carbon up and get stuck. (By the late 1970s it was teflon coated and seldom stuck.) If you did a lot of short trips, it stuck and applied heat all the time, warping the carburetor and causing vaporlock stumble. If you did a lot of highway driving, it stuck in the hot position and never applied heat to the manifold when cold (less harmful, but poor cold driveability and more carbon formation).
A broken spring means it will sit in the hot position and not give you manifold heat when cold, so you will have relatively poor cold driveability (less vaporization of fuel). If you live in a warm climate, you'll never notice. If you live in a snow climate, fixing it will really help cold driving.
This was eliminated in 1992 in the Daks when the Magnum (multiport fuel injection) engine came out. It was found that computer control of the mixture via the injectors and AIS was sufficient to provide decent cold driveability. However, the 1992 FSM still mentions it, an error.
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250rdakota
Dodge Dakota
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9/16/2004
21:47:11
| RE: exhaust manifold heat control valve???
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I guess that kinda makes sense. In the winter I have a hard time keeping it idleing. now that you have told me that I have another question for you. Ive been having a problem with power loss. I use it to plow snow. when I start to spin it will bog right down and wont even spin a tire then when I let off the gas the engine dies. this is the same in the summer, If I start to spin it dies right down and when I let off the gas it will die. It just dont have the power that it should. It also will let out black smoke out of the exhaust when it is floored and not spinning. I just cant figure it out. any ideas?
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Bob Lincoln
Dodge Dakota
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9/17/2004
08:45:11
| RE: exhaust manifold heat control valve???
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First step is to check fault codes:
http://allpar.com/fix/80s-codes.html
Could be a clogged catalytic converter, or another of the emissions controls. Have you ever replaced any of them?
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250rdakota
Dodge Dakota
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9/18/2004
09:25:07
| RE: exhaust manifold heat control valve???
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Heres a list of what Ive done in the last year.
coil, plugs wires, fuel filter, cap rotor, air filter, And just the other day o2 sensor. It still runs bad and Im about ready to by a different plow truck. If I cant get it pin pointed this could cost tons buying ever part and hoping it fixes the problem. Do you have any other ideas. I tried running the codes and the service engine light does not flash at all I dont even see a service engine light on the dash. Oh ya that converter how do you tell if it is plugged? My friend thinks that my carb is messed up because it seems to be running real rich. But that could be more then the carb couldnt it? Thanks for the help so far.
kurt
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Just Looking
Dodge Dakota
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9/19/2004
00:09:01
| RE: exhaust manifold heat control valve???
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What i did to test the cat was drill a hole in the muffler before the cat then weld a nut over the hole (so i could test it more easily in the future)
With the plug out run it and see if it runs lots better.
OR
Plug a pressure gauge in to see what pressure is building up in the exhaust.
Most running rich troubles come from... To high of fuel pressure for carb to control fuel flow,
Badly tuned, or carb is dirty/old needs to be cleaned, rebuilt, or replaced
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Hey
Dodge Dakota
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2/18/2013
09:17:14
| RE: exhaust manifold heat control valve???
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I hope he fixed it in the past 8 1/2 years.
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