faraz

I have a Evo 8, 42,000 miles, factory clutch, street driving.

Recently, my engine rpm has started to shoot up fast from 3000 to 4000 rpm when I floor the gas pedal and first sign of boost builds up. This only happens in 4th and 5th gear, not in 1st, 2nd or 3rd. The rpm comes back down right away and the vehicle then accelerates normally like its supposed to. I don't understand why the rpm shoots up and comes down when boost comes? It also doesn't happen all the time, it seems to have a mind of its own, for example, it will do it once, then it wont do it for the next 2 minutes, and sometimes I cant replicate it at all.

Could it be clutch slippage? If it was the clutch, then wouldn't it do the same in 1st, 2nd and 3rd?

Recently, I had the A/C compressor replaced. Could it be that the accessory belt is not tight enough and slips on the crankshaft pulley when boost builds, causing the rpm to shoot up for 1 second? There is no belt whine at startup, but I am not sure if that's a good test for belt tightness.

Could there be something wrong with the engine software or stuck blowoff valve? There is no check engine light.

I can't think of anything else. Any suggestions?

Thanks!

4WS Tuning

iTrader: (73)

Slipping clutch for sure... Just a matter of time until it becomes for apparent.

Cheers!

Hiboost

iTrader: (9)

I concur, clutch is slipping!

BTW this is the Evo X area but luckily you posted a universally easy to solve question.

lousEVOxmr

iTrader: (3)

well....... wait a second here ,
if it doesnt sleep at wot in 1 ,2 ,or 3rd ...... why would it slip in 4 , when more tq is puched in lower gears , and more hp in puched in higher...
i might be putting my foot in my mouth,
my 2 cent

F1312T4

iTrader: (2)

The engine produces the same power regardless of the gear you're in. It's easier to transmit that power into forward movement in 1st, 2nd & 3rd gear, so since the the car is easier to move in those 3 gears clutch slippage is less likely (in the early stages of failure). 4th and 5th provide the most resistance to movement (taller gear), so its more likely that the clutch will give up the ghost.

lousEVOxmr

iTrader: (3)

wow thanks ill go to bed tonight with a little less retarded in me lol..
thanks !

faraz

Why is the problem intermitent? Also should i get the belt tightness checked out first before replacing he clutch?

F1312T4

iTrader: (2)

The symptoms you are explaining definitely point towards a slipping clutch. As far as why it would be intermittent could be a couple of reasons, it could be because its in the beginning stage of wearing out, typically when they are at that threshold they will only slip when they get hot. Also, when you build boost you could be making just enough power to exceed the holding power of the worn clutch, then as boost tapers your torque curve drops, reducing the power the clutch needs to hold. Again, as the clutch wears more you will find that it will be come easier and easier to get the clutch to slip. When I eventually decided to change the clutch in my Nissan, I could put it in first gear, let the clutch out with the parking brake engaged and it would idle in my driveway. I wouldn't waste your time with the serp belt, that would have nothing to do with the symptoms you're describing.

faraz

Thanks for all the help.

Any suggestions where to buy a new disc, flywheel, t/o bearing, clutch cover and pressure plate from? Should I also buy a flywheel pilot bearing?

sprez420

wow gay so my clutch is slipping as well!!!!! same thing happens to me, when i step on the gas at 3.5rpms i can hear it spool then when i give it full gas the car pulls but then the rpms drop then they go back up and pulls normal to 7k rpms's

Sunwalker12

^happened to me a couple weeks ago, I was chasing a misfire for a while (only a slight hesitation in 5th under hard acceleration)....then it started in 4th and now she jumps a grand. New clutch and CMC here I come (thanks to Carolina Dyno)...install is tomorrow YAY!