Expert: Sean Halliday - 12/6/2007

Question
94 Gmc jimmy 2wd/ all power/air/mpi tuned well /new manifold gasket/checked for vaccume leaks/ Some times I strat up after engine has been run for a while and the engine speed races too fast to put in gear / some times if i let it run for a while  when this is hapening the computer seems to slow it down to normal happens regularly/
????????? your thoughts ? Thank You Ron Smith / little Rock

Answer
Could be a leak at the intake.As the engine heats up the metal expands and seals the leak which will let the car idle properly.May also be the idle speed control on the throttle body.The TPS.Throttle position sensor although this would cause the engine to stumble and idle erratically when warm.Try a leak test with some water which is safer than using aerosols such as brake cleaner as some people do.Spray the manifold with water when it races and if the engine slows up immediately, then thats where the leak is.I assume the air flow system is good?The rubbers and hoses?.Make sure your throttle linkage isnt sticking as well and travels freely.