Under no or little boost, it runs fine. When you hit .5 bar and above, the car bucks pretty bad and sputters. The boost drops dramatically when this happens. This all started happening after a battery reset and I have driven 160 miles since then. Any ideas? Spark plugs? Its a Evo 9

 

spark plugs will deff do that. change them. if that dosnt work then if u had a tune on the car u might have lost it for some reason if your battery was off for to long. anytime u take a battery off u should put a 9 volt battery into your accessory port...aka cigg lighter socket

 

You can lose the tune by disconnecting the battery? It was probably disconnected for an hour. That's sucks if that's the case.

 

NO, you can't LOL...

WTF, the tune is written to the ECU and battery disconnect will only affect short and long term fuel learn trims and idle.

Best thing is to perform an idle learn after the battery is disconnected.
Connect the battery, idle without hitting gas for 10 minutes.

Going back to Tune... If that were the case, everyone doing a clutch would need a retune or anyone changing a battery,LOL

 

Thanks, going to try that now. How long does the battery need to be disconnected to be reset? It still idles at 1k so I'm assuming the tune is still there

 

Plugs, make sure air filter is clean.

 

What plugs would be good - Its a Evo 9 with these mods - (making 22lbs boost)

M2 Camshafts, Valve Springs / ARP Headstuds / Turbo-Back Greddy Evo 2, 3in Dp / Buschur Duel Pump Fuel System / Aeromotive FPR / ETS 3.5in Intercooler / Injen IC Piping / Greddy RS BOV / GST Open Airfilter

 

I have some iRidium in stock heat range, that ok with the above set up? Any need to regap or just leave plugs in their stock form from box?

 

and nothing else was done while that battery was disconnected? did you work on it or something? why did you un plug the battery?

did you check to see if your maf is plugged in? couplers still on tight, no boost leaks?

change the plugs and see if it changes anything

 

Do you have duel maps? if so try switching. If your daily map isn't the one that the ecu recognizes as the default then when power is lost it will switch. the tune will be held by the C-mos in the event of prolonged power loss.

 

I disconnected it to clear a gas cap evap code. Cel never came back in those 160 miles, but now I can't have any fun. Stock heat range plugs fine?

 

No two maps that I know of anyway. Where would a switch be typically? Never heard of have more than 1 map other then a Cobb ap

 

^ o sorry u must know everything. do some research

 

and yeah go with stock plugs

 

WRONG...You need to stay away from cars and stop posting bad information....Since you told someone else to search, may I suggest you come into the Ecuflash section and grace us with your ECU knowledge lol...

OP - Your root cause is not your spark plugs. If the car ran fine before you disconnected the battery, I suspect your plugs are (were) fine. Have you checked for a boost leak (one of the most common problems with the evo) ? I don't know what issues / symptoms you had that caused you to disconnect the battery, but a boost leak would cause you to run poorly.