03 wrx 154k stage 2 invidia dp and g200 Bullwinkle tune for the last 50k ish miles. drove to work and school car acted 100% normal get gas park car on the drive home it wwouldnt go over 5-6 lbs. only things ive done to the car was belts and oil change thoes were done last thursday and monday. The car will rev past 4k so I dont think its in limp mode. the car feels like it wants to go over 5 lbs and shutters after I let off the gas idle is normal vac is sitting at 18-20 at idle. My guess is bad gas. But any advice will help.
ya stock bcs, ill give the wastegate arm a look, ill reset the ecu ive always done that by removing the battery connections and touching them together, ive never done it on a car with a tune and im guessing it wont effect the tune if your saying to do it.
Won't effect the tune. No need to touch the cables together. Just pull the negative cable and then press the brake pedal (or anything else that'll draw current). Check the c-clip on the wastegate arm too. If no codes pop get a boost leak test (since datalogging isn't an option in this weather).
What pressure does it normally idle at? My car is usually around 21 inHg. 18-20 would indicate a boost leak to me.
its always been between 18-20 hg thats normal a car doesnt maintain the same vac while idle it varies with idle rpm ip using a prosports gauge
so I was on my way to o'reilly to see if I had any pending codes, coming up to the lot the car was still acting weird. I parked went inside and got the scan tool plugged it in no codes brought it back in and car is boosting normal but there is some hesitation from 0-5 psi then after 5 its normal. also how would I check the WG I dont have a vac tool (apply and remove vac when the car isnt running). Could this be a plug issue I did the plugs like 30-35k ago with stock plugs not any colder or hotter.
possibly stuck bypass/blow-off valve? My Turbo XS valve has stuck open before only allowing 5-7 lbs of boost at WOT. i gave it a tap with a dead blow and the piston started sliding again.
I was about to suggest the same thing. It could be sticking open, and then snapping closed after some delay (and only closing sometimes). Is it an aftermarket unit? If so, I would open it up and clean it out. Also, visually check that the wastegate arm is properly connected. You should be able to do this externally. I don't think you'll have to remove anything except possibly the turbo heat shield.
Could definitely be a fouled plug(s) or bad gas like you mentioned earlier. Really hard to tell without a datalog. If you want to continue to check possible mechanical issues, then try a boost leak test next as a post maf leak can cause similar hesitation conditions as what you're describing.
I'd try to figure out the problem before throwing parts at it (especially if you have to pay for the parts!).
