My recently purchased Evo bucks at steady cruise, misses at idle, and hesitates coming off a stop. The car accelerates just fine. Replaced the previous owner's bov with a oem ix bov, and figured I'll plug in my obd2 scanner as I take it around the block. I noticed the map sensor data bounces a lot on steady cruise, it'll also read 24-25 in/hg with the car on, engine off but 10-11 in/hg at idle. Curious I tried my other cars, and they will have a constant map sensor reading at cruise. I would think the map sensor is faulty. Is there have current link to an evo 9 fsm? I'd like to test it before I purchase a new map sensor.

 

Which map sensor do you have?

 

oem

 

Its always gonna change with different throttle and load.
If you have cams even more so.
Sounds like a tps symptom.

And also a vaccum leak. Do you have a wideband and what does it read when it happens.

 

I have initially check vac lines, IC piping, and around intake manifold, everything seems to check out. I understand different throttle points and loads will yield a different reading for each different parameter. However I don't think the map sensor readings should be erratic given one load and one throttle point. In my case steady state cruising, the readings change as much 15 in/hg. Even at idle the readings are bouncing around although not as severe as it does during cruising. Comparing to my other cars gives a constant reading in the same scenarios, thus leading me to believe the map sensor is going out. Obviously each car is different in the way they operate, which is why I'd like to find a evo 9 fsm.

 

I have a stock map sensor you can borrow if you want to try it out. I'm in Wellington but will be going to the DIA tomorrow. Let me know if you want to meet up. You could post in the Evo Club of Colorado facebook group, I'm sure someone closer to you can let you borrow one to troubleshoot.
Did you do a proper boost leak test or did you just visually check the vacuum lines?

 

Pressure test of course. I appreciate the offer, I'll let you know if I decide on it, .