I have a 1990 Ford F-150 5.0 4x4 Automatic. The truck has 120,00 mile and is a great truck. My problem is as I go down the highway with the cruise control on the truck will suddenly start smoking, not out of the exhaust but from somewhere under the truck. I replace the dome cover gaskets. I checked the rear main, and cannot find the problem. Someone told me to replace the pcv valve. When I did the problem got worse. Can the egr valve be causing the problem. I have had people follow me and it definetly smoke from under the truck and not the exhaust. I would appreciate hearing from anyone who might be able to tell me what to do next.
Thank you
Lou

 

Lou,
You got me on this one. I have never heard of anything like it.
Is there anybody have any ideas.
I'd think you have an oil leak somewhere leak something on the exhaust converter cause you problem, but it would have nothing to do with the cuirse control. The cuirse control only has a few components, the control switches, speed sensor, amplifier, servo and vac dump valve, non of which I think could cause this problem. I guess I'd first try looking into any vacuum hose miswireing

 

I had about the same problem wih one of my motors,it turned out to be the gaskets at the end of the intake had blown out. I had a heck of a time finding it.

 

What engine are you running? If it is a V8 check leaks around the valve cover gaskets. If they are leaking on the exhaust manifold, you will notice smoke under the vehicle. You will also smell oil burning. On older Fords that was open to the atmosphere, this was a common thing whenever the engine was being starved for air. Not too sure about these new computerised systems that are completely closed. Old mechanics don't die, they just forget who they are. Carl

 

Please don't take this as an offense.. When you say the leak was at the end of the intake, do you mean the Intake Manifold Gasket? If so, what you were expereriencing was not an oil leak, but a water leak. I suspect. Yes, a high pressure water leak would look like smoke, but you would also experience a loss of water which would make the engine run hotter than normal. Carl

 

Loum,
Just heard of a recall about some cruise controls causing smoke and sometimes fires! Get it checked out quick

 

Well....I am gonna take a stab at this one. BLOWBY! And the only reason I am thinking this is becasue the fix that I would have suggested (replace the PCV valve) caused more issue than reliefe. My guess is that the valve stems are pretty worn for the number of miles, and that your engine is actually building pressure under the valve covers and it is being forced out of any place it can find. On the old carburated engines you could pull the air cleaner cover off and soak up a quart of oil if the blowby was bad enough. Solution...valve job with new valve guide inserts, or make sure that they get re-knurlized before they are bolted back together.