94 F250 w/351 startup and idle issues, MAPS? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 11-26-2004, 07:34 PM Thread Starter
 
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94 F250 w/351 startup and idle issues, MAPS?

When starting up my truck, it will die after starting, then will usually puff black smoke, then starts, then it will idle with a rhythmic surging. Then, it will go ok down highway, and settles down. Is this the MAPS sensor?
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post #2 of (permalink) Old 11-27-2004, 07:58 PM
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Re: 94 F250 w/351 startup and idle issues, MAPS?

Could be, but the surging makes me think of the IABv. If your not getting any codes, i would pull off the air intake hoses to the throttlebody first and check for carbon buildup on the throttle plates. If present, most likely it is also in the *idle air by-pass valve* passages that is mounted to the side of the TB. It needs to be unbolted and cleaned out with carb cleaner the plates can be cleaned with a rag soaked in it. If i would start by looking for a vacuum leak.

also, some earlier 5.8L EFI`S had an issue with oil coming up into the pcv valve and due to the location on the rear of the upper intake plenum, dump oil into #4 cylinder, i would check your pcv system while your at it for excessive oil. the cure is to plug the original hole and relocate the port on the plenum to the middle by tapping a new hole ( pipe thread). just an afterthought though, not necessarily pertaining to your situation.
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