Engine stall - gas petal freezeup

1995 Oldsmobile, 62000 miles, 3800 engine series II, runs fine except:

In winter when temperature is about 40 deg. F or less the car always starts O.K. but while driving it when temp gauge is almost all the way warmed up and when it starts to fall (when thermostat opens) the engine will suddenly run rough and quit and gas petal becomes frozen in place. I have to jab gas petal hard with my foot to release it. When I restart the engine all is fine again and remains fine. If the car is allowed to fully warm up in the driveway it does so without the engine ever quitting. The engine light does not come on when engine quits.

This happens almost always each day in winter (90% of the time).

Local mechanics never heard of this before. Any clues?

Reply to
Alexm
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Yup, frost and a dirty carb or TB. I have seen that happen from frost grabbing onto dirt at the linkage or pivot points in carbs and Throttle bodies.

TB's and carbs can frost up just at that 'vapor point' temperature.

Usually the cable end is gunked up too. A good clean with WD40 or even a throttle body spray cleaner should really help it out.

Mike

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Reply to
Mike Romain

A classis case of throttle body icing caused by the cooling effect of the expanding air / fuel mixture below the throttle plate(s) is what you are experiencing.

This is a common aircraft engine issue.. It traditionally happens more often when temps are just slightly above freezing and the humidity is fairly high.

Check all your sources of throttle body heating.. some cars use the engine cooling water piped into a jacket surrounding the throttle body, some use exhaust gasses in a similar manner and some have a "stove" on one of the exhaust manifolds and use a thermostatic control to pipe hot air into the intake to prevent this problem.

The clue here is that you feel the throttle pedal sticking. This is being caused by the icing around the throttle plate(s) jamming them in the body bores. The restricted flow is what causes the stalling. The idle speed control systems on computer controlled engines are also prone to this problem. After the stall occurs, the engine heat rises up into this area and melts the ice, "curing" the issue for the moment!

This problem was extremely common in carburated engines and was usually worsened by a build up of carbon in the exhaust "riser" passages that provided hot exhaust gasses to passages under the carb used for heating the throttle area. These cars usually had a manifold heat valve on the exhaust manifolds to direct the hot gasses around the carb base during warm up.

Someone with GM experience with your 3800 will probably pipe in here with some specific things for you to check on your engine.

I owned a 1955 Buick V8 that was absolutely undriveable in a freezing rain or snow storm because of this problem. Removing the heads and manifolds to clean out the "coked up" riser passages to the heated area under the carb really helped, but it still would ice if conditions were right.. Too bad, this was in the days before heated air intake systems and other corrections for this problem were used.

Let us know what you find...

Bob snipped-for-privacy@comcast.net

Reply to
Bob Flumere

Thanks for your suggestions, Mike and Bob. I have printed them out and will show them to a local mechanic or two. Strange that local mechanics are not familiar with the symptoms - perhaps this doesn't happen very often with today's cars.

AlexM

Reply to
Alexm

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