After having a wideband and an MBC installed in my Evo I decided to have it retuned by a reputable shop in my area. They did not have time to dyno tune it, so they "rough-tuned it". They also put in the tephra mod so the CEL flashes when knock is detected. My wife was the one who picked up the car, as I was in Afghanistan. She immediately noticed it was misfiring above 4500 rpm at WOT. She stopped and called them, they advised her to stay off the throttle until they could throw it on the dyno. She went back a week later. Same issue. They found the plugs fouled and replaced them, as well as swapping the coils. Also replaced the BOV (apparently mine was functioning) They still could not find a solution and turned the boost down to 16 psi and sent my wife home, saying it must be a fuel issue.

Fast forward two weeks, I came home on R&R, installed a walbro 255, and tested known good FP relays from a friends Evo. Still have the same issue. Since I have been able to drive it a bit I have made some observations: it only misfires at 100% WOT over 14.5 PSI, and before I tore out and returned wideband (if I'm paying someone to do something I can do myself, it better look good) it read 11.5/11.6 at WOT.

Prior to the MBC install/reflash the car Never had issues misfiring at WOT (I spent a lot of time there) and that was at 19-20 PSI, on stock fuel pump. Can a ****ty tune cause this problem?

Returning to Afghsnistan in 2 days, trying to decide if I should have the current shop work out the problem, or send it somewhere new. Prior to this I have had no problems with said shop, and they have done a good amount of work on the car since I've been deployed

Its an 05 w/ TBE, Intake, Forge MBC and BOV, and Walbro 255.

Thanks,
-Seth

 

Yes it could, simple thing to check is plug gap.

 

Plugs are OEM NGKs, gapped to .26

 

I'm having the same issue. Any codes? My wideband pegs out at 11.1 as soon as my turbo spools and then it feels as if it misfires numerous times when going over 4k. Hopefully mine is just tune related

 

The cam position center failed about a week after the issue presented itself, but since it was replaced there have been no more codes.

 

In my situation, I replaced an fp black with an hta35. I haven't been retuned as of yet (oct 10th appt) and my car is heavily modded on e85, 2.3l but we are having what seems to be the same issue. What it came down to me was either

1. tune
2.bad front o2
3. Bad map sensor (I'm on SD)

if I figure it out when I hit the dyno, I'll let you know...

 

Thanks. I'll let you know if a retune solves the problem.

I was asking if a tune could cause the problem because I've addressed all the ignition/fuel sources (except injectors. Stock injectors should be more then enough for my mods) and it never happened prior to this tune. Don't know who did the last one as it was done before I bought the car in 09.

 

I had/have a misfiring issue also, if I throw in new plugs itll run perfect then overtime it starts missing more and more. Mine are gapped around.023....When I had a bad knock sensor it (wiring was chaffing right where it comes out) was also misfiring like someone shut the key off while in boost, new knock sensor and ran sooo much smoother, then new plugs and no more popping at idle or mis at boost but hows your plugs look? Hows the top of your pistons look? Wet with oil or fuel or dry? I would prob go to a different shop, seems like they didnt want to help and just sent your wife on her way.