...hi all.
Yesterday i tested my EVO9 MRs top speed with ECU-Flash from the german tuner Koch. (he has won sveral Tuner awards from the german car mag Sport Auto).
ECU was flashed 3 month ago.

So, yesterday on the Autobahn:
Top speed was 168 miles w/o head or tail wind. Car performed very nicely with a steady top boost of 1.4 bar and going from 100 to 200 k in less than 12 secs (honest stopwatch . Everything was perfectly fine.

Going another 50 miles cruising 90 miles i recognized that power and boost had dropped (1.1 bar only), apart from that car was doing alright.
But in idle the car is very rough and almost dying, stuttering and then going up tp 1500 revs dropping again slowly again, almost stalling. Then this repeats. Keeping up the revs the using the pedal the car runs ok.

My thinking was that i have a boost leak / vacuum leak somewhere. So i checked for lose hoses on CBV, BC-Solenoid, IC, throttle body and so on, nothing to be seen.

Any ideas? What could i look for?
Could it be a broken MAF?
How can i check if i have leak? How to find its location?

THANKS all.

 

Could be a lot of things, as always, but you're describing something that happened to me as well, and my answer was not good news...

I'd just installed an AEM EMS and thought I had a good tune, too. I didn't. (My own fault, tho!)

Anyway, does the car still behave this way? I.e., you got it tuned, took it out, was happy with the results until "something happened" and now it always runs poorly, not just after you've "run it hard"?

Because if that's the case, then I'd say try this: Warm up the car, then with a bunch of rags covering everything around the oil cap, briefly remove the oil cap while the car is running. If it's healthy, some air will blow out, with some spatterings of oil as well. If it's ill, you'll see blue-ish smoke come out instead.

If that's the case, then go get a compression test to confirm it, but you may have blown a cylinder or two...

Best of luck!

 

Check the PCV Line to the Intake manifold. Recheck for Boost leack

 

where you at?? Im in Stuttgart.. I might be able to check your lines and help with a compression check, as well as all connections.. Good luck.

 

Thanks for the help, guys.

Lucky me, it was only a clogged MAF.

Unfortunately i had cracked my air filter housing a couple of month ago, and waiting for a new one i fixed the housing gaffer tape. A little piece was sucked in and clogged the MAF. i didnt see that the first time a checked the MAF since i wasnt able to spot the black gaffer without proper daylight.

I was alos lucky that i didnt damage my compressor wheel..... But you have to be lucky sometimes....