S14 SR wants to die when gassed and sputters under boost

Ive searched the technical section with no luck so… here it is.

Swapped an s14 sr in my s14 and it wants to die as soon as I let off the gas. Even if I hardly touch the gas and then let off, the revs will drop and the car will nearly and sometimes stall. It does the same on start up as well. If it makes any difference its a kouki sr, ecu code NA and a MAFS with the part number 22680-69F01. The only after market parts are a walbro 255 fuel pump, cone air filter, aluminum dual core rad, and a 3" turbo elbow. And there IS a stock recirc valve. Another problem is that it stutters and kicks under boost.

Just like this video of someone else’s car. (Couldn’t find the diagnosis that this guy came up with)

http://s35.photobucket.com/albums/d175/devilishfantasie/?
action=view&current=CIMG2151.mp4

Any help would be greatly appreciated. Thanks.

did u upgrade the fuel pump when u did the swap??

Yes forgot to mention that. Walbro 255 was installed.

Maybe the alt or alt fuse? Sounds similar to what my skylines problem was and it was the alt fuse

recirculating valve? or aftermarket blow off valve???

^^ same question. Also check for boost leaks.

K ill check those things. And its a recirc. Thanks. Ill post results.

blow spark plugs kinda do the same thing, but check for boost leaks

Check your base timing, if the CAS has been moved while that engine was in transit that can screw it up. Should be 15 BTDC iirc.

Swapped alt fuses just in case, had the alternator checked a while ago and it was fine, day ago I took the mafs off and cleaned it with electrical contact cleaner and went over all the piping tightening everything up.

I dont think its the plugs… but ill be swapping a friends in to check soon. As for the cas… How would I check that? I know where the cas is and all but my knowledge kinda ends there.

Also, I believe the car is in “limp mode”. Doesn’t wanna rev past 2.5 - 3k.

wehn it doesnt rev past 3k isn’t that a sign that the maf is bad?

Yeah thats what I’ve kept reading. I’m gonna check voltages and then post results.

a dead maf or bad one wouldn’t necessarily stall the engine though. It should still run, just like shit.

it does run… but it runs like poop… its just that when the throttle is pressed and let off the revs drop usually below 500 and nearly stall but the car doesn’t always necessarily stall.

So to sum up real short:

  1. Nearly dies when gassed and let off (sometimes does die)
  2. Wont go over 2.5-3k rpm (Limp mode?)
  3. Before it went into Limp mode it would stutter and kick back and forth during boost.

Sounds like the maf… make sure the connector is seated properly. Start the car and have buddy wiggle it around while you rev it up and see if you can get a stable run. Sometimes its just the boot that connects the maf and sometimes its the wires that were extended from the harness. Often its not soldered properly and breaks with corrosion and vibration and such. That would be my bet but there are other possibilities.

Try wiggling it and let us know what happens!

I checked the voltages today and one was 1.28V and the other was 14.48, but that was with a cold running engine on idle
The car seems to rev fine when not under load (neutral)
Took spark plugs out and they were BLACK!!! I cleaned them, took it for a spin, it revs past 3k now but still stutters really bad when boost kicks in.
I connected a boost gauge to it and was running 5psi, then I connected a boost controller and turned it up to see if it will boost more and it did but still stuttered like crazy.
Any other tests I can do for the maf? My buddy has a s14 sr but his maf is a tiny bit different (zenki), my connector is oval and his is rectangular.

Thanks for the inputs everyone!

Little update. Changed coolant temp sensor as the resistances were off. Cleaned the MAFS and throttle body. Got voltages for the MAFS: 1.2V at Idle and 2.5~V at 4000rpm. The car is no longer in limp mode, and it doesn’t stutter under boost. The idle is a little better now (less likely to stall after the gas is let off) but the car is WAY down on power. It almost feels NA. Im suspecting a big boost leak… Any tips on how to check other than the “spray soapy water everywhere” method? A DIY setup would be nice.

Thanks.