Engine braking while coasting?

[turboplz]

Still learning things about this 99 awd v8 mountaineer. One thing that I have felt, or noticed on occasion, is what feels like automated engine braking while I'm cruising and coasting down a long grade.

Is that normal on these trucks? My sister's Nissan Pathfinder does it, but that's the only other automatic truck I've ever driven that has it built in. Keep in mind this is the first automatic vehicle I have ever owned, so forgive me if it's common knowledge! I've always been a manual trans guy all my life.

 

[Joe Dirt]

It's not active engine braking like hill descent, but there is a decent amount of driveline drag, especially as compared to a manual trans. If you know anyone else with an AWD V8, you might drive it just to get perspective and know that something more isn't dragging on yours...

 

[turboplz]

Hmmm, it must be something causing the drag then. When going down a hil, I can feel it "engage" sometimes.

Guess I should look into that, perhaps one of the calipers is starting to stick. It does feel as though I downshifted a gear in a manual trans to do an engine brake, but it doesn't always do it.

 

[1996BLKBauer]

I believe my 96' AWD does the same thing you are talking about. It seems to slow down when I am going down a hill at times, I believe it may be something with the transmission down shifting, or something with the torque converter, because most of the time I sort of have a surge, but not faster, just slower. if you get what I am saying.

 

[budwich]

In some of the trans (at least my 96), there is a "coast braking solenoid". It should not be "activating" if you have overdrive "operational" and are in that gear... my take on its function. You could try deactivating overdrive and see if you notice a difference in your "coasting".

 

[crazymind]

Do you know if that selinoid is on the 5r55e? There are time mine coasts fine than other times it'll act like something is holdind back.
Sorry to high Jack your thread

 

[budwich]

From my quick on-line search, it would appear so (my "ref" for 96 only talks about 4R55 and 4R70). Hopefully, someone else with 5r55 documentation will give an absolute answer.

 

[yavapaires]

Hmmm, it must be something causing the drag then. When going down a hil, I can feel it "engage" sometimes.

Guess I should look into that, perhaps one of the calipers is starting to stick. It does feel as though I downshifted a gear in a manual trans to do an engine brake, but it doesn't always do it.

How about the fact the computer finally closes the throttle (through the IAC valve), and what you are feeling is the engine compression holding the vehicle back?

 

[turboplz]

How about the fact the computer finally closes the throttle (through the IAC valve), and what you are feeling is the engine compression holding the vehicle back?

I'm currently trying to source a definition file so I can look thru the strategy and see what all is built into this ecu. I don't think the throttle control that you are referring to is exactly right, but I think I know what you're getting at.

A lot of Ford strategies have what's called decel fuel cut, where between a certain RPM range (typically 1800-2200 kick in) and closed throttle scenario, the engine while completely lean out the a/f ratio causing an engine braking of sorts.

I've only tuned manual transmission engines, but this may very well be prevelant in the automatic trans strategies as well. It would also explain why I don't always feel it while coasting (ie, the rpms are below that 1800 rpm kick in range).

 

[lounge lizard]

mine will only do it when I drop it out of over drive. if I have it in over drive it will roll with very little engine drag.

but if I drop it out of over drive it will act as if an engine brake was applied.

 

[radman]

My 99 5.0 AWD exhibites the same symtoms sometimes. It only has 83K on it and I have owned it since new. I belive it feels like the torque convertor un-locking on down hill coasting and it usually only occurs at speeds above 50 mph.

 

[turboplz]

My 99 5.0 AWD exhibites the same symtoms sometimes. It only has 83K on it and I have owned it since new. I belive it feels like the torque convertor un-locking on down hill coasting and it usually only occurs at speeds above 50 mph.

Has it done this since new, or only recently has it started this?