high idle when shifting?
#1
high idle when shifting?
I noticed right before my tranny went that my rpms wouldn't drop below 2k-2500 inbetween shifts when I first started the truck. It would sit and idle at normal rpms but once in motion when the engine was still cold the rpms wouldn't go below around 2500 causing rough shifts or I'd have to shift from 4500 up to the next gear to smooth out the shift. Is this an IAC problem?
#4
It seems like warmer days it doesn't do it as frequently but if it's less than 40F outside you can pretty much bet on it happening.
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#11
Thing is.....it runs perfect after about twenty minutes! I just hate to run it up to 4500 on every shift when the engine is cold like that until it stops.
#12
One more suggestion.....have somebody press on the accelerator (gently, like you would driving it) while you are watching for the throttle plate to come back to the idle position. Do this while the engine is cold. If the throttle plate comes back to the idle position, then the problem is something else, like the IAC valve.......
#13
First of all, without modifying the calibration, it is not possible to totally eliminate the RPM hang between shifts. It is there for emissions reasons.
On the other hand, the RPM could be higher than intended. Here are some likely causes for this:
1) IAC is sticking as mentioned above.
2) Closed throttle TPS voltage is out of range and not telling the PCM when it has transitioned from part throttle to idle mode. Allowable spec is 0.53~1.25v at closed throttle but a voltage near 1.0 is ideal.
3) A temp sensor is out of spec as mentioned above.
On the other hand, the RPM could be higher than intended. Here are some likely causes for this:
1) IAC is sticking as mentioned above.
2) Closed throttle TPS voltage is out of range and not telling the PCM when it has transitioned from part throttle to idle mode. Allowable spec is 0.53~1.25v at closed throttle but a voltage near 1.0 is ideal.
3) A temp sensor is out of spec as mentioned above.
Last edited by V8 Level II; 03-26-2008 at 08:49 AM.
#14
The throttle plate not returning fully to the idle position would throw the TPS voltage too high.....
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#17
Most post dont say what they have but I know that this was an issue that turned into a TSB from Ford. My 04 would do the same thing till you almost came to a stop then come back down to standard base idle. Mine was intermitant and was never the same rpm when it did it. From 1500 to 2500 plus. Ford tried to tell me that it was factory that it did it. I aggree that it is in the PCM but not a 2500 rpm idle.
I think it was TSB 514. I have posted the same issues either on here of RPS (or both). Do a search and you'll find it.
Slightly higher than non moving or base rpm is ok. Higher than 1000 to 1200 and thats bad.
I think it was TSB 514. I have posted the same issues either on here of RPS (or both). Do a search and you'll find it.
Slightly higher than non moving or base rpm is ok. Higher than 1000 to 1200 and thats bad.
#20
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