High/inconsistent cold idle
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Freshman User
Joined: May 2004
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From: San Diego, CA
High/inconsistent cold idle
I had the rough idle for a while, but Oct flash cured. Just recently I've started getting a "high idle" at each cold start (not that cold... 60-70 degree weather). Engine immediately goes to 1100 RPMS when started. Then alternates between 1100 and 1200 RPMS for 5-7 minutes. Dealer says it's normal but I'm not convinced. Mostly due to the recent start of the symptom. Seems kinda dumb that the PCM would take a cold engine to 1100 RPMS before oil pressure was up... Anybody have any thoughts?
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Got Diesel?
Joined: Jan 2004
Posts: 4,345
Likes: 21
This is normal operation of the 6.0L Motor.
When your motor senses cold temps... it "boosts" the idle up from normal. Step on the brake or "go pedal" and it backs down to the lower idle. It is programmed this way for several reasons...
1) A diesel needs a hot glow plug to initiate the "start process".
2) A cold engine has a hard time compressing and burning diesel fuel.
3) A slow idle in cold weather (or what your engine believes is a cold motor) raises the engine RPM's to allow faster warm-ups and to prevent "cold soaking" of the injectors and cylinders. The hotter the motor the more efficient the process and the better performance you will get.
4) Idle will start out slow (normal) for a few seconds then bump up... well after oil pressure has been established.
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Next time the idle "bumps up"... touch the brake and it should come back down... if the motor senses it is still cold, the idle will go back up again.
Good luck,
Jeff
When your motor senses cold temps... it "boosts" the idle up from normal. Step on the brake or "go pedal" and it backs down to the lower idle. It is programmed this way for several reasons...
1) A diesel needs a hot glow plug to initiate the "start process".
2) A cold engine has a hard time compressing and burning diesel fuel.
3) A slow idle in cold weather (or what your engine believes is a cold motor) raises the engine RPM's to allow faster warm-ups and to prevent "cold soaking" of the injectors and cylinders. The hotter the motor the more efficient the process and the better performance you will get.
4) Idle will start out slow (normal) for a few seconds then bump up... well after oil pressure has been established.
____________
Next time the idle "bumps up"... touch the brake and it should come back down... if the motor senses it is still cold, the idle will go back up again.
Good luck,
Jeff
Thread Starter
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Freshman User
Joined: May 2004
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From: San Diego, CA
Jeff,
Thanks. Am familiar with reasons for a "warm-up" idle, but the engine is not reacting that way. First, it just started doing this - In May, not December when it was significantly colder. Next, the engine speed is not stable - alternates between 1100 and 1200 - not "hunting" but abruptly alternating. And lastly, it won't idle down with a touch of either the foot feed or brake. I end up driving away with the high idle and slamming the tranny around a bit as a result. It also screws up the downshifting strategy. I asked Ford to prove it was normal with some tech document, but they can't.
Oh, and now I have an idiot light telling me of an engine problem, so I guess I'll be going back to the dealer again (3 times in only 3300 miles).
Thanks. Am familiar with reasons for a "warm-up" idle, but the engine is not reacting that way. First, it just started doing this - In May, not December when it was significantly colder. Next, the engine speed is not stable - alternates between 1100 and 1200 - not "hunting" but abruptly alternating. And lastly, it won't idle down with a touch of either the foot feed or brake. I end up driving away with the high idle and slamming the tranny around a bit as a result. It also screws up the downshifting strategy. I asked Ford to prove it was normal with some tech document, but they can't.
Oh, and now I have an idiot light telling me of an engine problem, so I guess I'll be going back to the dealer again (3 times in only 3300 miles).
Last edited by SZMatters; May 25, 2004 at 09:34 PM.
Got Diesel?
Joined: Jan 2004
Posts: 4,345
Likes: 21
Wish you would have explained more in your first post as you did in your second post... I had no idea that you knew about the cold idle issue??
I would get a PCM flash update to most current, or if it is most current they did not follow the "rule" book for proper procedure (must hook up batterycharger to ensure 100% power when programing and cycling the ignition.
Good luck,
Jeff
I would get a PCM flash update to most current, or if it is most current they did not follow the "rule" book for proper procedure (must hook up batterycharger to ensure 100% power when programing and cycling the ignition.
Good luck,
Jeff
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Freshman User
Joined: May 2004
Posts: 41
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From: San Diego, CA
Thanks Jeff. Will try it. The truck goes in tomorrow night and I'll try to convince them that another flash may help. Now that I have the idiot light, maybe there will be an error code to follow. We'll see. Thanks again.
