Common problem with multiple fixes. I haven't found my fix yet. This is a big problem as I spend a great deal of time on unpaved roads where I need to drive around 10 mph. When the idle problem first started it was more of a high idle problem. Even warmed up the idle would jump up and accelerate me to 20 mph in low gear. And would then drop back to regular idle. Occasionally would surge up and down more quickly. Engine would start right up and idle in low 30 degree weather but had to crank a while when warmed up. As the idle got a little worse I replaced the air idle control and cleaned the throttle body. Didn't fix anything and the surging slowly got worse. The idle surge became a mix of entended high idle with abrupt drops to slow idle along with extremely high idle at times and at other times a rhythmic up and down idle. It also developed a touchy throttle that would trigger surging/bucking issues. Ii then changed out tps with no fix. Scan showed a failure code of 41 so I changed the O2 sensor and still got the code 41 (lean) on scan. Next step replace the ecm. Still no change on idle (but starts better warm and seems to have a little more power at wot). Still showing a 41 failure code I did several resets to make sure it wasn't in memory). I checked output voltage on O2 sensor and it was extremely low even though exhaust smells a little rich so I tested to see if I was getting current for O2 sensor heater and it tested OK. If I pull the vacuum line for map sensor off manifold the idle smooths out but is a little high. Capping off port on manifold gets me a pretty good idle. Scan test with vacuum line off map sensor gives me a failure code of 42 (rich) ao I think this rules out O2 sensor or wiring. My question is where do I go from here? I have also tested the air temperatue sensor and coolant temperature sensor and both look Ok. Also checked for vacuum leaks. This Bronco runs great on the road and idle is OK for stop signs and short red lights but no more than 30 seconds before surging or bucking starts up.
another surging idle
- Thread starter tueycal
- Start date
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Rons beast
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Hey TUEY,
Welcome.
What's the info on your Bronc? Year , engine, etc.
Looks like you hit most areas with your checks. A thought is the EGR valve. Carboned up and/ or sticky.
Good Luck
Welcome.
What's the info on your Bronc? Year , engine, etc.
Looks like you hit most areas with your checks. A thought is the EGR valve. Carboned up and/ or sticky.
Good Luck
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