Question about 1988 Ford Bronco
Engine in park, speeds up , slows down. Runs but will act like it's starving for gas.
Look for a vacuum leak. Most of the 302's of this vintage we get in the shop are suffering from a vacuum leak causing poor idle or surging. To do this, start the engine and allow it to warm to normal temp. Then, take a can of "Brake Cleaner" and with the straw attached to the spary top, direct the mist along all the vacuum hoses and the gaskets around the intake manifold, and alont the fuel rails. If there is a vacuum leak, the rpm's will pick up noticably and you will be able to pin point your vacuum leak.
Posted on Mar 08, 2015
Probably a loose or missing vacuum hose. Check the vacuum diagram under the hood and look for loose or cracked hoses.
Posted on Apr 22, 2014
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Posted on Jan 02, 2017
Check and see if the EGR valve is leaking, to check this spray water on it at idle, if the water steams off the valve is leaking and is the source of your problem, also are you sure you hooked the new DPFE sensor up right? re-check it..
Posted on Nov 23, 2008
Most auto parts stores will scan the engine codes free or allow you to use theirs on site. Scan the code and post it back here for additional help.
Posted on Jun 24, 2009
The IAC (idle air control) may be stuck from dirt or malfunctioning.It's located in the intake near the throttle body.Remove it clean with carb cleaner and reinstall
Posted on Nov 23, 2009
Testimonial: "Thank you for response. Actually had IAC off and was clean inside. Resistance within range 9 ohms but voltage signal at 12.5 V rather than 10.5 V"
Idle air control valve is the problem. "idle motor" tap it with a hammer it should temporarily solve your problem. it is right on top by the throttle body.
Posted on Dec 19, 2009
Tips for a great answer:
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is commonly caused by a dirty automatic idle speed control valve and
throttle valve but always run a OBD2 fault code as well as the
cleaning procedure. Buy a can of throttle valve cleaner (do not use
carburetor spray cleaner!) from NAPA or Carquest (made by CRC
chemicals) and spray it into the air intake while the engine is
running, use up about 1/2 the can, engine will try to stall hold the
speed up, shut it down and let it soak for 30 minutes, restart and
blow out the remaining fluid, shut it down and disconnect the
negative battery cable for 5 Min's to reset the base idle control
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