Hello, I recently purchased an evo 8 with 78k miles. I noticed upon decceleration I hear loud rattling noises coming from the lower engine area. I also have an issue around 70-80mph where the entire car begins to vibrate when I take my foot off the gas (only in 5th gear). Lastly, it appears I am only pushing roughly 5-8 PSI at most when shifting at 4k rpms(no boost controller on car currently, idk why?). After doing some research, I am confident the rattling noises is the throw out bearing. I have a full ACT kit I will be installing shortly so hopefully that fixes that issue but I am a little lost on the other two problems. Has anyone experienced similar vibrations at high mph? Any insight/information would be greatly appreciated as I am not the most mechanically-inclined. Thank you!

 

Hey, Welcome & congrats on the EvO. Great to have ya on the boards!

Yeah, diagnosing stuff like this is tough for sure. Regarding the boost issue, a simple boost leak test should be done, but before that just check all the piping & clamps. It may be that simple as a loose clamp. Many of us run the ACT HDSS clutch so lets get that installed!

Not sure about these vibrations? Could be a no. of things. Probably need to check the state of the tune on this EvO. Are you sure the 60K service was done?

Cheers, Joe

 

Thank you for the warm welcome. I am having the clutch and TOB installed tomorrow so I will have my mechanic further look into the boost leaks. Hopefully that will also give insight as to why it is vibrating. I will provide an update soon, very much appreciated for the info.

 

What flywheel is on the car? A lightweight will cause alot of resonance and amplify the clutch noise especially on decel.

 

Well ****, I'm feeling cocky cause I just helped 2 dudes fix their cars on FB.
Wheel balance is good?
Axles/CV joints are good?
Can you tell the guys who actually know this stuff more about the car?
I love Evo's and anyone who gives them love...so I'm immediately heavily emotionally invested in your cars health. Tearin' up here guy. ~sniffle~

 

5th gear in some Evo 8 transmissions was bad from the factory. My car was one of those affected. As I recall, the repair amounts to a new input shaft and a new 5th gear. My car would vibrate at around 60 mph with light accelerator application but smooth out at higher speeds. I think it depends on how bad the gear is. I drove my car with this problem for about 100K and then replaced the transmission.

 

Congrats on the purchase and welcome.

I would just make sure you have a good reputable mechanic who may have some experience with the Evo. This forum and the guys here have tons of info to help.

you might just want to take your mechanic out for a spin to show all the issues

 

So if you are in 4th gear at 70-80 mph, it does not happen?

FWIW when my car wasn't holding boost, it was the wastegate actuator.

 

Thank you everyone for the replies. My mechanic installed the new ACT pressure plate, disk, flywheel, throw out bearing and the rattling is completely gone (clutch is butter btw). Boost controller was also installed and it is now pushing roughly 20 psi so I am happy about that. He explained the vibrations are because the car is in low rpms in 5th gear (2.5k rpm) and thats normal. I do however feel a loss of power in 5th gear, like it jerks back slowly but is barely noticeable. I will have the tuner look into it after getting new injectors and fuel pump. Does anyone have recommendations for e85? You guys are lifesavers!

 

What situation is power loss? Like boost cut maybe?
Really helps to share as much info about a problem as possible so smart-aleky(how DO you spell that) fools like me shut up and the actual smart guys chime in.

 

I’d fix the issues before throwing E85 power at the car. What kind of motor mounts do you have installed?

 

CEL recently came on and threw 2 p0300 codes (random misfire). Did some more research and have not been able to narrow down the problem. I am replacing the spark plugs today just to be safe but has anyone else had this code? How did you fix it?
Thank you

 

I have had that code before spark plugs and wires fixed it.

 

brining this back from the dead recently threw the same codes? With pretty new spark plugs, ever figure out what caused it or fixed it?

 

code p0300 has a storied history on these forums of being caused by drivetrain harmonics and other BS. you can search around on here or on google for "evo p0300 5th gear" or "evo p0300 tsb" (technical service bulletin issued by mistubishi). drivetrain harmonics was a problem with the '03 and '04 models especially. if you have the freeze frame data from the obd reader you could look at things like engine load and throttle position % and get an idea as to whether you're seeing this under low load cruising conditions vs boosting/acceleration. a lot of people with a lot of aftermarket work just straight up disable the code. i can't speak to the wisdom of this decision but not a lot of people take it seriously unless it's accompanied by boost or unusual driving behavior like stuttering, hesitation, or vibration