evojed

Need some help. When under acceleration (doesn't have to be at WOT), everything is going fine until around the 4500 - 5K mark, and then my RPMs and acceleration drop significantly and I start accelerating again. The drop in RPM's can be anywhere from 500 - 1500K. Under WOT, it seems that the first part of the acceleration is half baked and once the RPMs drop and start rising again, the real acceleration starts. Any ideas?

Thanks,
Jed

JTB

iTrader: (23)

Has it always done this? If not, for how many miles?
It might just be a bad tank of gas and the knock suppression is kicking in.

EVOtook

Are you stock? If not what mods?

EvolvedDSM

iTrader: (3)

Clutch?

ez76

iTrader: (5)

agree, sounds like a slipping clutch

Ultor

iTrader: (2)

Is there a Service engine soon light?

MalibuJack

iTrader: (5)

It could be a bad tank of gas or fuel cut.. But I say this every time, if you've got a few thousand miles on your plugs.. Change them or clean and regap your plugs.. Also you don't say if your car is stock or modified.. But before you become too concerned.. wait until you get another tank of gas.. reset the ECU.. if it persists, check for vacuum or boost leaks on the pipes and hoses, and change your plugs (if you have anything aftermarket such as a filter upgrade and exhaust upgrades) go one step colder and gap them a little tighter than stock.

SinCityEvo

iTrader: (3)

I agree. Slipping clutch. Plan for a new one.

JTB

iTrader: (23)

If it was a clutch wouldn't the RPM rise and not drop during acceleration?

A slipping clutch is indicated by a rise in RPM without an appropriate increase in speed.

SinCityEvo

iTrader: (3)

Actually, it would drop because it's slipping, and then rise again. It would only rise if you are on the gas fighting it, but at normal cruise, it would drop, then you will feed it more gas by habit and it would rise again. I know someone who just changed their Evo clutch and it was the same symtoms as described.

JTB

iTrader: (23)

This makes sense. What you are saying is that when the clutch is slipping at constant throttle the car is trying to catch up to the speed of the engine but also the engine is being slowed by this as the clutch is trying to match the speed of the two. I don’t believe that it applies in this situation.

For this to match his description though the clutch would have had to be slipping slightly all the way up to 4500 RPM in 2nd, 3rd and 4th gear. At this point the clutch is beginning to bite more, accelerating the car but pulling the revs down, then fully engaging for the acceleration to continue?

In my experience when a clutch is beginning to go I will have symptoms like accelerating hard in 3rd gear and the acceleration will not feel as hard as the rise in RPM indicates – that or problems getting going from a stop.

A good test for a failing clutch is to bring the car up to about 40mph, put it in 4th gear. It should now be at about 2k- 3k RPM. Dip the clutch and apply some gas to raise the RPMs and then gently reapply the clutch. If the car quickly brings the engine back down to the earlier RPM and then begins to accelerate then the clutch is fine. If however the clutch starts slipping and the RPMs do not fall then your clutch needs to be replaced. Don’t do this too many times as it is hard on the clutch!

I have also not had a clutch fail on my Evo so maybe the symptoms are different.

evojed

Thanks for all the replies. The car is stock. My wife took it out and quickly came back going something is wrong with your car. She described it like a regular four cylinder with the turbo trying to kick in.

Thanks,
Jed

evojed

Looks like the clutch is the issue. I am having it towed to Mitsu today. Thanks again for the help.....

Jed