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Howdy all,
So my F150 (with 4r70w) has a weird issue. If I jump on it (only briefly) and then drive normally it gets stuck in a high idle/late shift mode. Sometimes it won't even shift until 3500 - 4000 RPM. If I stop and restart it will usually go back to normal (depending on how warm the tranny is, the warmer it is, the less likely to fix on restart). Now I understand that if you give it a lot of gas it will shift later, but like I said, it get's stuck in this mode even if I have a light foot after. The really weird thing is that it does this after cruising on the highway for a while. Also, the OD light does not flash.
As I'm writing this, I just realized that a common thing is warm tranny fluid. I'm not sure if it's the tranny because the high idle and the fact that it will shift fine if babied. There are no codes.
Here's what I've done:
Flushed tranny fluid and filter (full flush, not just the little bit with the filter change), replaced TPS, replaced PCV, replaced IAC valve, replaced a few vac lines, and cleaned entire throttle body (including EGR valve).
P.S. I've searched and searched and then searched some more and can't find much info. Hopefully somebody might have an idea where I can look next.
Your description matches a TPS that is not linked to the throttle plate shaft except by friction.
The TPS is normally slotted into the end of the shaft.
This could even hold the throttle open some amount and cause a high idle condition.
The TPS has a lot to do with shift points.
Shutting down the motor then restarting changes the idle, tells me the PCM' s taking on a new a new 'zero' set.
The TPS takes on a new zero point every time the PCM is repowered.
It's called a floating zero point.
.
On the old Mustangs and Fords, some owners thought resetting the TPS position to a certain voltage gave them added performance but what they did not know was the ECM reset the zero point the next time the motor was started.
The reason this is designed into the system is to get out of any issues from TPS wear and resistance changes with temperature. This makes the TPS a low replacement item over their life span.
Let us know if that is the problem..
Good luck.
Yes, I agree, the TPS makes sense. Albeit your description is the most informative I've seen (love FTE), based off of slightly less information however, I replaced that first. I will reinspect the installation. Thank you kindly for great info!
Howdy!
Ok so I pulled the tps, and it mounts with a little tension on the spade from the shaft, so the throttle is turning the tps correctly. I also checked the voltage and the tps is functioning correctly.
With nothing to go on, it was a good try.
The high idle is air getting in from some place other than the throttle body same as you opening the throttle.
Are you sure the throttle is not sticking open a small amount.
The transmission can't cause a high idle because there is no link to cause it.
However, a higher idle could affect the shift point during that event same as what happens when you lift your foot off the throttle.
My feeling is your missing an air leak that may be vacuum level and temperature sensitive.
The transmission is electric operated for shifting so the PCM dictates when shifting will occur either up or down..
If a valve body solenoid is in trouble the PCM will see it as a short, cross, open or slow to operate.
Any mechanical issues beyond the solenoids can't be detected by the PCM.
Good luck.
Thank you bluegrass for your input. Much appreciated! A vacuum leak seems to be the way to go given the temperament of the issue, but I'll be darned if I can find it. I did think about the shift solenoids, but you're saying that would throw codes? Did I understand that correctly?
"If a valve body solenoid is in trouble the PCM will see it as a short, cross, open or slow to operate" or even stuck..
Yes, it looks at the voltage and current signature of each circuit as a way to detect an issue.
Most of those codes are in the 7xx number range.
Have you looked at the rear of the intake manifold?
Good luck.
I looked at the rear of the throttle body, is there anything lower? I guess I'll go and look. I forgot to answer the other question. When I took off the throttle body and cleaned everything (TB plate and elbow) and cleaned the plate and housing (twice) I made sure, the second time, that the plate opened and closed completely with slow and fast movement.
I'll take a at some of those hoses and report back.
The vac line going into the elbow was loose. When the system called for EGR it created the vacuum leak there. I put some rtv there for now just to make sure. If that works, I'll replace the line and elbow.
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I forgot to answer the other question. When I took off the throttle body and cleaned everything (TB plate and elbow) and cleaned the plate and housing (twice) I made sure, the second time, that the plate opened and closed completely with slow and fast movement.
