Hello Everyone,

I just bought an Evo 8 recently and I'm new to the platform. Car ran fine during test drive, had about 110k miles. Now, any time I go past 1/4 throttle and have any sort of load on the drivetrain, the car bucks really hard. Cuts power, tries to go, cuts power again, etc. Car is completely stock, except for a BOV and different cams, according to the previous owner. He also said he replaced the clutch with another stock clutch. He also put in a new TPS sensor, it looks like he made a pigtail on the existing harness to the connector. He is convinced it is related to the TPS. I have a code for a rich primary O2 sensor and a speed sensor. The speedometer/odometer work fine. I also have all three of the ACD lights on. So far, I have done a boost leak check, changed the plugs, checked the MAF(completely clean, look like it might be new), checked the TPS voltages, which were low so I adjusted the sensor. I found a leak around the throttle body seals so I replaced those. I have a tactrix cable on the way to take logs. Nothing I have done so far has had any impact on the drivability. The car sat for awhile in a shop according to the previous owner. No obvious boost leaks outside of the throttle body seals.

Any thoughts where I should go from here?

Any input would be much appreciated!

 

No boost gauge? Sounds like it's hitting fuel cut.

 

Correct, no gages at all, ordering AEM gages to install, trying to isolate this problem in the meantime.

Fuel pump maybe?

 

Fuel pump wont cause fuel cut if that's what you're getting at, but some gauges would be beneficial at this point to see boost and AFR's. Your description sounds like fuel cut but it generally takes more than 1/4 throttle to build enough boost to hit it. Does it get easier to do in higher gears vs lower?

 

you can log the throttle position sensor when you get your cable and that should tell you if you have a tps problem

does the car have a tune?
cams and different bov... car may not be tuned correctly and you are building to much boost at low rpm, part throttle.. .and not adding enough fuel.

 

Car is not tuned as far as I know. It is as bad, if not worse in 4th and 5th gear. The car doesn't even try to build boost, it literally cuts power as soon as the turbo starts to spool up. What does a bad TPS signature look like in the logs, idle position starts too high or too low?

The O2 sensor running rich code suggests too much fuel being added though?

 

just log the tps, then turn the key on (dont have to start it), then start the log...slowly push the throttle down and then let back up and make sure you in general have 0 - 100 - 0

what happens if you just mat it... does it pull clean?

 

The more throttle input, the worse it breaks up. It bucks violently at full throttle.

 

maybe your BOV is backwards