Can a clutch slip on deceleration?

8

87lc2

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Oct 16, 2005

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Nov 6, 2009

#1

• Nov 6, 2009

• #1

I have a strange issue with my car. When in gear coming to a stop (off the gas) it feels like the car will come out of gear for a second then get right back in. No wierd noises or anything from the tranny, just feels like its slipping or something in gear coming to a stop. The clutch grabs great and never slips while driving so I dont think its the clutch. I would appreciate any opinions or experiences anyone has with this. TIA

 

G

GDTrumbo

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Jan 22, 2009

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Nashville, TN

Nov 6, 2009

#2

• Nov 6, 2009

• #2

If it doesn't slip upon acceleration, it won't on deceleration.

That almost sounds like the "hanging idle" issue some just can't stand. It's originally designed to do this for emissions reduction.
Your probably just noticing it when it's in gear rather than out of gear.
I have noticed mine do this since I bought it in '02. Doesn't really bother me much though.....

There is a simple remedy to calm this down a bit if you want. Do a search on "IAC restrictor mod". There's a couple ways of doing it.

GT

 

8

87lc2

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Oct 16, 2005

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Nov 6, 2009

#3

• Nov 6, 2009

• #3

Thats sounds abou right, thanks for the info. The idle does hang a bit when coming to a stop out of gear. Cleaned the IAC but it didnt make a difference. Ill look into that, thanks again.

 

trinity_gt

10 Year Member

Jan 31, 2003

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Canada

Nov 6, 2009

#4

• Nov 6, 2009

• #4

If it's what I think it is, it's normal. When you decelerate and take your foot off the gas for an extended period of time, the engine computer (PCM) will actually turn off the fuel injectors. GM used to call this "DFCO" mode or "Decel Fuel Cut Off." I don't know if Ford has a similar terminology or not.

Anyway, the PCM will only let engine RPM fall to a certain point before turning the injectors back on so as to prevent stalling and instability. This usually happens at fairly low RPM, perhaps ~1200RPM or so. When the engine gets fuel again, it "wakes up" and some of the pure compression braking effect is lost. This can feel like a bit of a "slip" or "jump" and it's normal.

 

8

87lc2

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Oct 16, 2005

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Nov 6, 2009

#5

• Nov 6, 2009

• #5

That sounds about right too....guess its nothing to worry about either way. Ill make a restrictor plate this weekend anyway as my cars idle does hang a bit. Thanks again guys

 

patman0911

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Jun 5, 2002

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Tuscaloosa, AL

Nov 6, 2009

#6

• Nov 6, 2009

• #6

What TrinityGT said - the transition between fuel on and fuel off is not very smooth or subtle. It's very pronounced in my car, especially with the loud O/R H-pipe and it's a weird sensation that is hard to describe - feels and sounds like the motor is being sucked inside out. The car tips forward a little under engine braking and then when the injectors finally kick back in again it feels like a giant hand just let go of the car.

Is it more noticeable in lower gears and coasting down from higher RPMs, and especially down a hill?


How high does the idle hang? It's supposed to hang for a couple of seconds before it drops down to the lowest idle but if it's hanging at, like, 2K, then you do have a problem

 

8

87lc2

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Oct 16, 2005

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Nov 6, 2009

#7

• Nov 6, 2009

• #7

patman - yes, it is very noticeable coming down from higher rpms and down a hill. It feels exactly as you described. Why would they design it like that? Feels horrible, like someone holding the car and then letting it go just like you said. Oh well, at least nothing is wrong with the car.

As far as the idle, it doesnt hang bad at all. It hangs at 1k for maybe a second then drops right to 750 where I have it set at, so its not terrible. I would like to try the restrictor just so it doesnt hang at all between shifts.

 

patman0911

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Tuscaloosa, AL

Nov 6, 2009

#8

• Nov 6, 2009

• #8

They put that in because it's an easy way to boost mileage - you wouldn't believe how good your mpg is when your not using any fuel!

The hanging idle sounds pretty normal. Yeah, the revs don't fall very fast on these motors. If you try to drive around clutchlessly using rev matching it's like 5 seconds on upshifts between pulling it out of one gear and sliding it into the next. Not that you should be driving around like that anyway.