1G Misfire > 4k RPM

[Awesomewheeldrive]

So, as a few of you know ive just got my engine in. I was trying to do the motoman break in. And well, first pull i was in 2nd flooring it and as soon as i hit 4k rpm and only at 7 psi (yes i have an aftermarket boost gauge) the car bucks and sputters. I know its not fuel cut because i have a 255lph walbro. I also have a 2g maf and 550cc injectors. Car runs flawless under 4k even in boost, but anything over i get misfire/sputter/jerky-ness. Ive got bpr7es plugs gapped at .029. I just replaced the ecu with a rebuilt ecu with new caps. I just want the car to run right..ive spent 6 months and all my extra money in this car and im just getting exhausted.

 

[blucas1984]

check for boost leaks and check base timing.

 

[Awesomewheeldrive]

No boost leaks... I think it maybe the fuel pump going out because it takes a good 5-10 seconds to fire when cranking

 

[Awesomewheeldrive]

Built a blt. No leaks. I check my fuel pressure and its solid. Pulled the fuel pump, it is a 255 just like i was told. Base timing is set at 6 degrees. I know mitsu says 5 but i upped my boost to 16psi so i think 6 degrees should be okay. Im running bpr7es right now, but im going to get new wires and a set of bpr6es today and see what happens.

 

[jpLaserRs]

Check your vac line to your wastegate mine did that and it was a pin hole in it 2.89 cent hose fixed it.

 

[Awesomewheeldrive]

Checked wastegate line as you said and nothing.. I changed plugs and wires. It picks up more on bottom end but still breaks up in higher rpm. I can brake boost 16psi at 3000rpm and no sputter or hesitation. But as soon as i hit 4500 still misfires like crazy.

I ended up hooking up my wideband last night and when im at a steady speed im at 14.1-15.3. But when im WOT im between 10.0 to 10.4

I also should mention that even in neutral it misses at high rpm

But in neutral it doesnt miss until 5500k

 

[Tiki2777]

Check your plugs, wires, and coil pack. Most non-BL stuttering in boost at med-high rpms is due to bad plugs. I would make the gap a bit smaller. (spark blowout) It fixed my stuttering when i had your problem.

 

[Awesomewheeldrive]

Im not getting blow out, i also tried new plugs today. Tried to gap them all the way down to .022 and no change. I did however notice that my last pull i didnt look at the road. I watched my uego. And it went to 10.0 and stayed there so apparently im running way to rich since the uego doesnt read lower than 10.0

 

[Awesomewheeldrive]

Idk what to do anymore. Ive got a 2g maf 550cc injectors and an safc with a wideband and no matter what i do/how much fuel correction i give it, as soon as i hit 3500rpm my a/f goes up uo and away. Its fine boosting under 3500. I can brake boost it and my a/f will be at 10.8:1, but when the rpms go higher than 4k the a/f goes to 15:1 or higher. No matter how much i corect it

 

[herms99gst]

Have you checked your tps and mas? What about fuel pressure at 45-5400 rpm's?

 

[herms99gst]

It sounds like a vaccum leak tho. Is the wideband new? Have you put a vaccum gauge on the car and checked your vaccum? Should be a steady 18-22 with very little movement.

 

[Awesomewheeldrive]

Wideband is brand new.. So its my boost/vacuum gauge. Vacuum is a strong 21-22hg . Tps is good according to my multimeter and according to my safc. I stil need to check the mas

 

[b3n_91]

I had a similar problem I changed out my spark plug wires and problem solved!

 

[Tyeler18]

Definitely sounds like a spark issue. I'd start with replacing your bpr7es with BR6ES gapped at .028 not BPR6es.

 

[NHerron]

Okay I'll clarify first

High AFR at cruise (14.3:1 - 14.9:1) That's pretty normal. Light throttle, cruising, and hot idle, this is what you should see, it's in closed loop operation

WOT pulls 10.0:1 - 10.5:1 is normal too. It's in open loop

But you say at about 4K RPM (idle or load), your AFR's begin to rise continuously UNTIL it starts to buck and sputter?

Or does it buck/stutter first and THEN do the AFR's instantly rise?

By the way, did you check the power transistor which controls ignition coils?

 

[fierosail]

replace plugs just because you can go wrong and they are cheep get soap water test for vac leaks do a boost leak test and check all sensor including the knock sensor.

 

[Awesomewheeldrive]

Ive already replaced plugs and wires. I did switch to bpr6es and accell 8.8 wires. I have an extra coil but its a 90 coil so i cant test use it. I think im gonna try to grab a coil off a n/t from the junkyard. And it drives perfect even at wot until it hits 4k rpm then it stars to buck. Under 4k my a/f is spot on. But as soon as i hit 4k my a/f goes to 14.3:1 and keeps going to 17.1:1. But this is only under load. I can floor it in neutral and it will shoot up to 7k pefectly. But when its under load it wont

And i was going to check the transistor but i dont know how to test it

Justed tested my mas. I was suppose to get less than 2 ohms and i got 112 ohms...... So im going to borrow my buddys 2g mas and see what happens

 

[Tyeler18]

I was JUST going to say, that sounds like a MAF problem. When we were defining the big map roms for the 3g community we were having the same problem. Something in our tables was causing a problem with the MAF going wild over a certain load percentage. I'd say your MAF is toast.

 

[Awesomewheeldrive]

Ya i was thinking its the maf and not spark because the maf is the only thing thay is going to make my a/f that messed up. And because the a/f im getting knock. And due to knock im pulling timing. And because im pulling timing its misfiring. A huge chain reaction of a hassle

 

[NHerron]

When does it start to buck and sputter? Before or After the AFRs begin to rise?

Runs good in neutral all the way through 7k+ now?

 

[Awesomewheeldrive]

It bucks sputters after the a/f starts to rise. Id say as soon as it hits 13.5 to 1. But in neutral its fine. Ill take a video and post it in a bit. That way everyone can hear it

 

[MetalMulisha]

I have the exact problem you are describing in my 95 talon. I'm down to coil packs and maf. Ive checked, and changed everything else. U hope you can pin point your problem!

 

[NHerron]

I would set the timing back to factory just to rule that out. After that watch the AF gauge to watch when it starts to buck during a WOT pull

 

[Awesomewheeldrive]

Okay idk what everyone is telling me about plugs, wires and timing. But just to say, ive already set my base timing to factory. Ive already switched plugs and wires. I bought a rebuilt ecu. And yes i did test the ecu and i did open it up and look at it. Its non eprom, rebuily, and new caps. I was able to borrow a 2g maf and rc 660's and those will be gettin put in the car when i get home. I also have another cas that i will wire in. And i borrowed a coil and transistor off a car that i know runs fine. So when i get home i will update everyone on whats going on

 

[MetalMulisha]

Okay idk what everyone is telling me about plugs, wires and timing. But just to say, ive already set my base timing to factory. Ive already switched plugs and wires. I bought a rebuilt ecu. And yes i did test the ecu and i did open it up and look at it. Its non eprom, rebuily, and new caps. I was able to borrow a 2g maf and rc 660's and those will be gettin put in the car when i get home. I also have another cas that i will wire in. And i borrowed a coil and transistor off a car that i know runs fine. So when i get home i will update everyone on whats going on

Good luck bro I hope you can pin point the problem, please do let us know what you find.