[SOLVED] Backfiring and misfiring hard

J

Joestegs

Greenie N00B Member
I recently helped my brother do a jdm engine swap on a 2008 speed3 and went through all the paces and its been running good for the past month+. So naturally I went out and bought my own speed3 with a blown engine and put a jdm engine into it, finished maybe a day or 2 ago and when we went out to test drive it as soon as I would give it anymore than maybe 5-10% throttle it would start jerking and misfire extremely hard to the point where it sounds like 2step. Also free revving it will sometimes stop increasing rpm and start backfiring and shaking the whole car. It sounds like the turbo is spooling super hard when it does that and I'm not even sure where to start from here. The guys I got it from said it was tuned for 93, for the intake and the stock de-catted downpipe, so all that stayed the same from the blown engine. When I first started it up it had a boost leak and a vacuum leak and I had forgot to plug the o2 sensors in. I fixed all of those and unplugged the battery for 10 mins to try to "reset" it and it had seemed to run great until I tried to drive and it started doing the backfiring. Any help would be appreciated.
P0193 p0113 p0102
 
Did you uninstall the tune on it? Definitely something you want done and back to base map of aftermarket parts with a new to you engine

Check all grounds and connections don't neglect the hpfp ground as it goes into coil pack / injector harness images (1)~2.jpeg

-Are you sure it's backfiring into the intake manifold and not after firing?
- check MAF connection and clean MAF sensor
-Might be worth cleaning that hpfp, if it is "tuned" with a catless downpipe you'll also want upgraded hpfp internals, perhaps the ones off the old engine - assuming seller actually upgraded them.
 
Awafrican said:
Did you uninstall the tune on it? Definitely something you want done and back to base map of aftermarket parts with a new to you engine

Check all grounds and connections don't neglect the hpfp ground as it goes into coil pack / injector harness View attachment 25825

-Are you sure it's backfiring into the intake manifold and not after firing?
- check MAF connection and clean MAF sensor
-Might be worth cleaning that hpfp, if it is "tuned" with a catless downpipe you'll also want upgraded hpfp internals, perhaps the ones off the old engine - assuming seller actually upgraded them.
Click to expand...
Definitely should've made sure the tune was gone first, I don't have an accesport and cannot afford one currently but I'm going to try versatuner out because I've wanted to get into tuning for a while, I have a cord on the way and will update when I get a tune on it
 
Awafrican said:
Did you uninstall the tune on it? Definitely something you want done and back to base map of aftermarket parts with a new to you engine

Check all grounds and connections don't neglect the hpfp ground as it goes into coil pack / injector harness View attachment 25825

-Are you sure it's backfiring into the intake manifold and not after firing?
- check MAF connection and clean MAF sensor
-Might be worth cleaning that hpfp, if it is "tuned" with a catless downpipe you'll also want upgraded hpfp internals, perhaps the ones off the old engine - assuming seller actually upgraded them.
Click to expand...
got the correct tune installed on my 3 but not much has changed, i tried to log it but i dont really know what im looking at so ill just throw it up on here. going to go check all the grounds and clean the MAF, probably get hpfp internals ordered too

Figured it out, I tried looking over the log again and realized actual fuel rail pressure was a flat line, which matches up with the code that I had that stated fuel rail pressure circuit high output or something along those lines, I check the rail sensor and it had separate and fallen apart, thanks for the help! She's running great now!
 

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