High Idle
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From: Fl
High Idle
Have A 96 ranger that is a manual 3.0, 2 wheel drive. The engine will idle up while driving with AC on and act like I have cruise control on. The only way to get engine to idle down is to shut off the AC. Engine will idle like this at times with out the AC on. Just about every sensor has been replaced, smoked the engine looking for vacuum leak, none found. Have no engine codes. Been trying to figure this out for sometime now with no luck. Even have taken to a repair shop. They could not figure it out. Hoping someone has run in to this before.
Welcome to the forum
Warm up the engine and let it idle
Unplug the 2 wire connector on the IAC Valve, on upper intake manifold by the throttle plate
Engine RPMs should drop to 500 or so, barely running engine, or engine may stall, either is GOOD, it means no vacuum leaks
If idle stays high then air is getting in from somewhere, more on that later
If RPMs do drop then it was the Computer that was setting the higher idle, OR the IAC Valve is stuck(clean the IAC Valve)
If you have or will replace the IAC Valve you can ONLY USE Motorcraft or Hitachi brand IAC Valve, other brands will cause what you describe
Better to get an old used Motorcraft IAC Valve from wrecking yard than a 3rd party brand
With warm engine idling(IAC Valve connected again) remove the Oil Fill cap from the engine and see if idle changes, might change a little thats OK, but shouldn't change alot
If there is a big change you will need to get a new PCV valve and clean its hose AND the breather hose that is connected to the oil fill caps tube
Engine off, remove the air tube on the upper intake and check if the throttle plate is loose, open and close throttle manually to make sure its smooth, no places its sticking
And stop changing sensors, my 1994 has all its original sensors and they work fine
ONLY sensors that need to be replaced are the O2 sensors, they run out of chemicals to detect oxygen in the exhaust, 100k miles or 12 years which ever comes first
New parts are NEVER TESTED, yours will be the first hands to touch a new part, so YOU are the Quality Control Department for the company that made the new part, they just warranty it, never test it
So never assume "it works" because its new, "all new sensors" just means you have A LOT OF TESTING TO DO, lol
Warm up the engine and let it idle
Unplug the 2 wire connector on the IAC Valve, on upper intake manifold by the throttle plate
Engine RPMs should drop to 500 or so, barely running engine, or engine may stall, either is GOOD, it means no vacuum leaks
If idle stays high then air is getting in from somewhere, more on that later
If RPMs do drop then it was the Computer that was setting the higher idle, OR the IAC Valve is stuck(clean the IAC Valve)
If you have or will replace the IAC Valve you can ONLY USE Motorcraft or Hitachi brand IAC Valve, other brands will cause what you describe
Better to get an old used Motorcraft IAC Valve from wrecking yard than a 3rd party brand
With warm engine idling(IAC Valve connected again) remove the Oil Fill cap from the engine and see if idle changes, might change a little thats OK, but shouldn't change alot
If there is a big change you will need to get a new PCV valve and clean its hose AND the breather hose that is connected to the oil fill caps tube
Engine off, remove the air tube on the upper intake and check if the throttle plate is loose, open and close throttle manually to make sure its smooth, no places its sticking
And stop changing sensors, my 1994 has all its original sensors and they work fine
ONLY sensors that need to be replaced are the O2 sensors, they run out of chemicals to detect oxygen in the exhaust, 100k miles or 12 years which ever comes first
New parts are NEVER TESTED, yours will be the first hands to touch a new part, so YOU are the Quality Control Department for the company that made the new part, they just warranty it, never test it
So never assume "it works" because its new, "all new sensors" just means you have A LOT OF TESTING TO DO, lol
Last edited by RonD; Apr 16, 2022 at 01:45 PM.
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