Bvullers

Hello, i'm new here and the owner of a 2004 5spd 192.
I have had the car for abour 2 years bur since a few days the rebuilt engine is in.
engine now has about 80-100kms on it (around 50 miles).
It runs now but is hesitant in low rpms, stuttering misfire and stalling.
its gotten better after putting the stock air box back in but i dont have all the parts of the intake so rn its only the box with a maf and a temporary pipe. It does however have the 3 vacuumlines connected and its not leaking past the maf.
this has made it drivable at low rpms.
Maf has been cleaned and swapped with a new one since i had it, no diffence.
The short term fuel trims seems to be at 23-26% and long term fuel trim and short term fuel trim bank 1 sensor 2 seem to be stuck at 0.0%.
ignition coils are bennetbuilt ones less than 200kms on them (ls coils) spark plug have been reused from before rebuilt since they had less than 50kms on them.
It throws a p0301 code so im guessring front rotor misfire.
I have pics if the spark plugs so ill add those in a comment.
its got a oil pressure upgrade and a sohn adapter when it comes to mods. And some gauges.
this issue was also apparent before the rebuilt.
gas milage is horible its gone from 65% to 40% in like 60kms.
engine has been rebuilt with oem parts and specs of the mazda manual.
reused housings and rotors in good condition.
above 4k rpm there is no hesitation and it puls strong no misfires or power loss.
Any ideas?
it also stil smokes a little when idling after cold start but since it has no cat and has been rebuilt so recently that seems normal to me.
after driving its gone.
I love to hear your suggestions😁

Bvullers

The spark plugs.
oh and i have checked for vacuum leaks with the cigar trick.

BigCajun

iTrader: (1)

The OEM intake needs to be intact and clean with the screens in place.
I would recommend new plugs and NGK wires, 50k is beyond what most folks here would recommend.
I'd also be sure there's a loom between the wires to eliminate the possibility of arcing.
I've heard of the Bennet LS coil kit, Idk if it could be a problem.

If it were me I'd buy some new Rev.C coils from a reputable place like Advance that has a lifetime warranty and try to get everything back as close to stock as possible to make troubleshooting less problematic.

BigCajun

iTrader: (1)

Also clean the ESS and reset the NVRAM.
(20 brake pedal stomp)

UnknownJinX

He said 50km, which is 30 miles, so the spark plugs should be okay.

Benett Built coils are based on the old BHR designs so it should work unless the coils are busted, but given that the OP only has issues at lower RPM, don't think that's the case.

I would double-check the airbox connections since the car is running very lean with such high positive fuel trim. And yes, the 20 brake stomps are worth a try.

Loki

iTrader: (1)

Focus on bank 1 sensor 1. Especially since you don't have a cat. Bank 1 sensor 2 is the post-cat narrow band O2, it doesn't do anything for fuel trims.

You'd ingesting unmetered air somewhere and it's compensating for that. Once the car is warmed up, what's the airflow in g/sec while idling at 800rpm? There are more nipples than the 3 on the accordion pipe, check the VFAD nipple under the throttle body. If that doesn't get you anywhere, check lines going to the oil injectors and the intake valve actuators.

UnknownJinX

He has a 192/4-port, so there wouldn't be a VFAD.

But yes, check for any potential leaks.

Bvullers

Its seems to be between 5.9 and 6.3. Idle is also jumpy. Cleaned the ess and also did the brake stomp but its still lumpy. Also the fuel trim is -18%/-25% guess i oversaw the minus before😅 So that would mean its running to rich? My spark plugs were also black but dry. So running to rich im guessing?.

BigCajun

iTrader: (1)

Ok, I read 50K, not km.