Question: What is your Engine RPM During Coast

[jayton13]

Hello,

I think I have solved my rough/wandering idle. I replaced my PCV and PCV grommet and it seems to idle much more consistently. I went ahead and put a hose clamp on the PCV hose also just to keep a good seal around the PCV itself.

The question I have now is what is your engine speed (RPMs) when you are coasting or between gears? Does it drop all the way down to normal idle speed (between 700-900RPM)? Or does it stay higher, at least for a little while?

When driving and between gears or coasting down my engine seems to only drop down to around 1500RPM at least for a while. Once I come to a complete stop, like at a light or something, it usually drops down to normal idle speed. So, the question is...

Is that normal or should it immediately drop down to normal idle RPM as soon as the clutch is pressed in?

Edit to add:
I have a 2003 3.0L with the 5 speed manual gearbox.

 

[85_Ranger4x4]

My 302 goes to idle.

Sounds like you may have a vacuum leak or something.

 

[superj]

I thunk my 3.0 stays higher for a secind or two when coasting. It was odd to me st first but i think i read its normal

 

[SenorNoob]

My 4.0 usually hangs around 1000 for a half second.

 

[jayton13]

OK.

I have checked every possible vacuum line short of doing a smoke test. No leaks. I think that is also verified by the fact that it idles exceptionally well when parked. Someone, somewhere, sometime has replaced the IAC on this thing, as it looks new-ish and I am betting is not an OE/Motorcraft part due to a lack of markings.

I have now tried swapping the following:
New IAC (non-Motorcraft part)
New MAF (non-Motorcraft part)
New TPS (non-Motorcraft part)

I swapped each of these independently to try and isolate the issue. There is no difference in performance when each of the new parts were in place.

If I were to GUESS, based on how it is behaving, it has to do with the dynamics of the aftermarket IAC. It just seems like it maybe doesn't respond as quickly as it should.

I am going to try and track down a Motorcraft replacement and see where that gets me.

Edit to Add:
Here is a link to something that appears to validate my suspicions: https://mechanics.stackexchange.com...ansmission#:~:text=Im going to,indeed the fix.

Probably means I am wrong.

 

[jayton13]

I am now learning that the system can adapt to the duty cycle values of various IACs.

Perhaps I just need to give it an opportunity to learn. I am going to try performing these re-learning cycles and see where that gets me.

 

[Jazzer]

I got a bad Motorcraft IAC some years ago and it had those exact symptoms. Replacing it with another MC IAC solved the problem.

 

[gw33gp]

It is normal for the idle to stay high when coasting. It is related to emissions. Typically, it should go to the normal idle after you get below a specific mph or stopped.

That is one thing I like about the Bama tune on my Ranger. The idle hang was eliminated. While shifting gears it drops to idle quickly and makes quick shifting easier. I also have much better engine compression braking when slowing down.

 

[jayton13]

It is normal for the idle to stay high when coasting. It is related to emissions. Typically, it should go to the normal idle after you get below a specific mph or stopped.

That is one thing I like about the Bama tune on my Ranger. The idle hang was eliminated. While shifting gears it drops to idle quickly and makes quick shifting easier. I also have much better engine compression braking when slowing down.

I went ahead and ordered a Motorcraft IAC, but I am beginning to think that what is now occurring is supposed to be happening.

I completed the idle re-learn procedure and now there is a lot less variability, but the engine will sit at around 1500 RPM no matter what until I come to a complete stop. It will then hover at 1500 for a few seconds then drop straight to regular idle and stay there.

Next question is...what is this Bama tune you speak of?