I was hoping some of the EVO experts on the forum could help me. My car, 2003 EVO, was running perfectly until I put about 5,000 miles on the car from August 26th to October 3rd driving back and forth from New Orleans, LA to San Antonio, TX escaping hurricanes. During that time, I had the car serviced (15,000 miles) at Gilman Mitsubishi in San Antonio. I had no problems with car at all after the service. About two weeks after I returned to New Orleans, I started having a weird drivability issue at higher boost levels.

As boost starts to build, especially at higher levels (20 PSI), but also at lower levels (10-15 PSI), the boost will hold as stable as a rock, but the RPMs will suddenly drop 1000-1500. For example, when it hits 4000-4500 RPM it will suddenly drop to 3000 RPM and slowly climb from there. Boost will remain stable the entire time – rock solid, with drop. Also, there are no codes are CELs.

I’m estimating it’s not a boost leak, due to the fact that the boost remains stable. I’m guessing it is either fouled spark plugs are some type of fueling issue (injectors, fuel pump, etc.). I bought new spark plugs and will install them tomorrow. I hoping this will solve the problem. Do any of the experts on the forum have any insight into this problem?

My mods are a turbo back exhaust with high flow cat, K&N drop in filter, JDM MR diverter valve, and the XEDE computer.

Thanks in advance.

 

Whoa! You are saying you are at full boost going through the rpms and at 4500rpm, your rpms suddenly drop to 3k??? It's not like the engine can suddenly spin slower by 1500rpm while still accelerating at full boost. Fouled plugs would just make your ignition breakup, which would cause sputtering and erratic boost. I've never heard of rpms dropping by 1500 while accelerating...

 

In order to drop while the car is in gear the engine would have to kind of shut off for a few seconds while it coasts down and then pick back up again. Is this accurate? Or do you push the clutch in and then it drops and picks up? If the clutch is engaged it cannot suddenly drop to 1000-1500 rpm's like an automatic. The clutch forms a locked solid connection with no ability to change engine speed independantly of road speed, unless it is disengaged.

 

Yes, this is what happens. It is seriously f'd up. I push the go pedal down, boost hits 20 PSI, RPMs build very quickly, boost stays stable, RPMs drop very quickly, then slowly climb - power is way down. It's really weird.

Thanks for the quick reply.

 

Thanks for the reply, joey.

Yes, the RPMs climb very quickly first, boost builds, RPMs drop even quicker, while boost holds stable. It's repeatable every time, more serious in hgher (4th and 5th gears). Do you think it could be clutch issue? There are no engagement issues.

Thanks again.

 

That could be the strangest thing I've ever heard. You're saying boost remains stable but you lose 1500rpms?? Then, does it climb back to 4500 and drop to 3000 again over and over in an infinite loop with you never accelerating beyond whatever speed you hit at 4500rpm with boost being maxed the whole time indefinitely?

 

Have you scanned the PCM for any potential codes?

Something like that has to throw a code unless your tach is just messed up.

 

I had kind of a wierd problem, one of my Xede wires came loose while hooking up a laptop to it, the car would go, sputter, and pop, and the car would die. I dont know if this is your issue, you can make sure you "push" in all the wires on the XEDE with your fingers, and see. It has nothing to do with the product, I just plugged in the xede to the lap-top without the extender cable. Could you have bad gas? there was kind of a gas shortage during the hurricane. Unplug your negative terminal on the car battery, wait 10 minutes, re connect and start the car without pushing in the gas for 5 minutes. this resets all, and may help.

 

Do the rpm's just "drop", or is there an associated shudder, or other wierd noise?

 

Dude, the clutch is slipping. Maybe not something to laugh about, but at least the engine is ok. It is slipping up to a certain rpm, then catching and dropping quikly, and then maybe slipping again. That is the ONLY way you can have the rapid RPM change that you are describing. When a clutch in a manual transmission is locked, then it is locked. Period. The higher torque multiplier in the higher gears normally means that these are the gears in which clutch slippage is first seen. You simply blow through the lower gears too fast to hear/see/feel the slippage until it gets pretty bad.

 

I guess it's possible that he's explaining the problem backwards, but I kinda doubt it. When the clutch is slipping, you feel it give way immediately as the RPMs shoot up, but you don't accelerate. when the RPMs catch, the tach drops and you start to pull again. What he's saying is the opposite. He said he accelerates normally up through the RPMs, but then the tach drops and he loses power. If he's really trying to describe a slipping clutch, then his powers of observation are severely lacking in this case.

 

Ok im not a mechanic or anything but to ME it sounds kinda like a fuel cut. i have a boost controller in my car and if im in 4th gear going about 40-45 mph, and hit it, my car starts to "hick-up". i know what it wrong with my car but i dont need to fix it yet cuz i know how to drive it but im not sure what is wrong with urs. Sounds like fuel cut but I honestly dont know. It does sound like clutch problems to but it were slipping the rpms would go up not down. If u just got a tune-up make sure they put in the right kind of spark plugs, and didnt leave anything disconnected. Does the rpm drop in any gear or just certain ones?

 

If it were fuel cut, his boost would not remain steady and the RPMs would not suddenly drop by 1500. Fuel cut just cuts the fuel immediately...it's like hitting a brick wall, and the boost falls off, but your RPMs don't unless you just let off the gas.

 

It is the strangest thing I've experienced. Boost remains stable, at 4000-4500 RPM it suddenly drops to about 3000 RPM with boost needle still at 20 PSI, then RPMs will slowly climb till red line, power is way down. No infinite loop. Boost is maxed the whole time. Uncanny.

 

True! Does This person have a boost gauge and know that its not dropping any psi or are they assuming. Sorry I'm not calling u with the car problems an idiot but nobody asked that question so i thought i would. ok lets assume there is no gauge, I still have no idea where im going with this?????? I dont know take back to the dealer.