Hey guys, let me know what information you need to help me figure out this annoying problem. I think once fixed it will help with the results on the 1/4 mile as it bucks there too.

Ok so I was cruising at 110km's in 5th gear and if I was to quickly tap the gas at just about a 1/4 peddle the car would start to buck. I was data logging earlier in the day and when this happened the ignition timing went do to 8°. I'm tuning with an Emanage and using duty cycle. Maybe that's one part of the issue (using duty cycle that is).

Video

http://www.youtube.com/watch?v=Bk1-ksg3wzo

Any ideas would be great. If I pres on the gas gradually this doesn't happen.

Thanks

 

Fidanza flywheel correct? My ride does something very similar, though not quite as pronounced. Last week I put the stock flywheel in, and its back to normal, I think it has something to do with the material on the ring. Do you still have the first gear stumble going on too?

 

I don't believe its the flywheel as the clutch was engaged. That was me just pressing the gas a quarter way on the highway in 5th. At the quarter mile I had the same issue in 1st and 4th. In 1st it was like my redline was at 5-6 grand and in 4th was straight when I shifted from 3rd to 4th. Once you let off and go back on its ok.

BTW PM coming your way

 

to me it looks as though the car goes super lean and for a split second detonates under load then levels off lean. I saw the readings drop to about 13.6 then continue climbing north to over 18afr while you were still in the gas As fast and furious as this sounds, I think you have a nasty hole in your part throttle fuel map You need to put in more fuel. It also looks as though you're passing through the open/closed loop point for the ECU at those speeds which could cause the car to stumble depending on the amount of change you have in fuel in your tune since the computer will fight changes pre-closed loop.

 

Currently I don't have any 02's connected. So as far as the ecu thinks its dumping fuel. Also when this occurs its within my regular tune. It's not like it goes to the top or somewhere it shouldn't. I added more fuel to the spot it goes to when this happens without success. I also found out that my fuel pressure gauge reading from the fuel pump also moves when the car stumbles, not by much though but it does it (fuel pressure sensor is at the input of the fuel rail).

You also mentioned you saw 18AF, that was it going to 21-22AF cause I let of the gas after it stumbled.

 

Are you using an Emanage Blue or Ultimate? Also, if this is only happening in first and 5th gear, are you using the same/similar cell values in the other gears? What about your J&S, is it lighting up or anything?

That's kinda normal, specially at the rpms you're at. I'm not entirely familiar with your setup, but are you using a FMU? You might need to bring up your base fuel pressure and reduce the rise rate.

Unless the sound is off on the video, you were still "in" the gas and AFR was climbing rather than staying steady (i'll give it mid-high 16's when you let out - but without seeing the tach, it's hard to visually tell). Think you can do another video that show's the tach and the wideband gauge?

I want to help, just don't know all the variables.

 

Do you have a Fidanza flywheel? If you do it will cause this problem. Not sure on the a/f, but it will cause a studder under partial throttle. I have had this problem for probably 5 years. There is not a problem under WOT, but at low rpm's when you push the gas it will shudder. Another thing you can try if you are sure you have a safe tune is to bypass your knock sensor (resistor), to rule that out. I was having suddering problems when I fist did my vq35 swap and it was because I had a faulty knock sensor.

 

Yes I have a Fidanza flywheel but I also have this problem at WOT (but only when you power shift and it sometimes happen it's not consistent @ the 1/4 mile). I'll check the knock sensor.

Mad-MAX_SE

I'm using an Emanage Ultimate, I don't have any o2's, no FMU, just a 255lph Walbro and 600cc injectors. On the drag strip its random. I've had it happen in 1st,2nd,4th, on the road I can feel it slightly struggle in some gears (J&S does not report anything) in 5th is where I cruise/can replicate the issue (sometimes). I can also definitely take another video if it helps.

 

Is this the situation at which it happens.

High load, Low RPM, WOT throttle?

How are your sparkplugs by the way?

 

Low RPM, Low Load. At WOT its random (only happens at the 1/4 mile). Sparkplugs should be good, it won't hurt to look at them again.

I also tried to take another video last night without any success. Maybe me retuning certain points is getting rid of the issue (doubt it though). I'll try again within a couple of days as the car is going of the road to replace a caliper.

 

I was heading to work today and while I was turning and slightly tapping the gas around the corner the J&S went all over the place. I think it went all the way to the middle which I have set for 1° per red dot if I recall correctly.

Maybe the J&S is to sensitive? The car didn't struggle or anything though. Yet when I was setting the J&S it took some good hammering to make the J&S detect knock. Ahh what a $%^#%$.

Also I checked for codes, I don't have any knock sensor codes. I'm starting to think maybe spark plugs? To be honest I've had this issue at the track last year without the J&S installed. This year i'm still having it but it's not that much ( a little more random).

Difference between 1 step colder plugs and 2 step colder plugs?

 

You don't need 2 step colder for your application. Double check your connections at the j&s, seems like something shakes loose with vibration.

 

I'd like to blame the J&S but this happened at the track last year without the J&S.

 

Ok need some help on this. I took a video of me revving the car in the drive way and the J&S light came on (roughly 4-5 red lights)l. Now I know it looks lean but thats because I'm on and off the gas. If you look good you will see 10-12 A/F. Maybe I should turn the sensitivity down a bit. Advice?

http://www.youtube.com/watch?v=LZPy7-CLmxg




After math...

 

Tighten your KS sensor to spec. check PM. If JS is going off while revving engine then it might be too sensitive, mine goes off like that but rarely. Usually it goes off on the highway when I leave the car in high gear and accelerate (low rpm, high load). my **** is not all they to the max but close, its at about 8 (0 being all the way counter clock, 10 being all the way clockwise)

 

Will check, not sure what my sensitivity is at as I adjusted it last year. Thanks

 

The J&S ignores the knock sensor if it senses more than five inches of vacuum. This is to prevent false detections during decel or light loads due to piston slap.

 

When revving (I haven't checked) doesn't the vacuum get close to 0? So that means if there is knock the J&S will light up as its accounting for the knock sensor?

I'm suspecting the timing ring on my fidanza flywheel isn't the greatest. Could this affect the overall timing and cause my stumbling/random J&S knock sensing? Also when I fire up the car the timing is being recorded at 5-7° shouldn't it be 15°? And to throw another thing into the equation my car will sometime not start. It would crank over then stumble then keep cranking and fire up. But sometimes the car fires up like it’s brand new.

Maybe my big issue is the flywheel and in turn is causing the car to hesitate on startup (sometimes) stumble on the highway and cause the car to knock due to bad timing? It's all random BTW and I have recorded a full boost 3rd gear pull and the timing seemed fine?

Think I’m on the right track or totally off in my conclusion that the flywheel is the culprit? I could change the sensor that goes on the tranny.

 

your car is "bucking" because its going too lean. Check over your fuel maps and look for anything that needs to be tweaked a little bit.

Did you do the tune yourself, or has it been on the dyno and recieved a pro-tune.

 

At this point I don't think it's my tune to tell you the truth. It's been on a dyno but that was only used for 3rd gear WOT runs. I spent 3 hours on the dyno without any bucking issues. Fidanza Flywheel is coming out this Wednesday. Then I'll do a new tune using duration. Not duty cycle.

If it was a tune issue I believe the problem would be consistent at the same location. At the track sometimes I have what seems to be a new redline at 5k. One run 1-3rd was perfect.
Then once I shifted into 4th the car appeared to have a redline at 3k. It's all over the place. I have one more thing to try out before I pull out the fidanza flywheel and install the stock one back.

Forgot to mention that once you let of the gas and then go back on it the car doesn't stumble.

 

Post up a video of you revving it with the car parked and I can help you a bit. You said you have no o2's you mean no o2's plugged into the emanage just the wideband right ? Bucking like you described sounds like an improperly torqued flywheel.

 

First post has the video of the car parked and revving. I did this again a couple of days ago and the A/F are 10-11. The fidanza flywheel is off and the stock one is back on. I guess tomorrow I'll see if it made a difference.

 

OK so I swapped out the flywheel (issue persists), retuned my map (issue persists), swapped out the sensor on the tranny and the sensor by the crank pulley (issue persists), changed the pigtail for the tranny sensor (issue persists).

Can it be coils? Aren't 2000-2001 coils with the grey dot supposed to be the good coils? I swapped my non grey dot coils with the grey dot coils (to be honest this was when I could replicate the stuttering issue). So i'll try to swap my coils back and see if that's the issue. But I've had this issue before with my old coils. (I'm rambling)

The last thing that can be the issue is my damn Z32 MAF. That's the last thing that would cause this damn behavior ), I could splice in another connector for my stock MAF?

Ohh forgot to mention...

I checked my knock sensor, it reads 560k at room ~22°c. I read this was a good value to have. Maybe when the car really warms up the knock sensor goes out of spec. I can drive the car around until the motor is heat soaked and measure resistance. Maybe?

Anywho any random ideas to help me solve this problem would be appreciated. I still need to check the CAM sensor but I swapped that out last year. But with my car you never know...

 

Update:

Have P1320 code right as the car fires up. The code instantly comes on.

P1320 refers to:

Harness or connectors
(The ignition primary circuit is open or shorted.)
Power transistor unit built into ignition coil
Condenser
Crankshaft position sensor (REF)
Crankshaft position sensor (REF) circuit

Things I tried:

I checked all the ignition coils to make sure they got the proper voltage from the emanage. All the coils get the proper voltage at idle and 2500rpm (as per FSM).

Will check condenser tomorrow at work as my DVM can't check the capacitance.

Is the crank reference the sensor by the crank pulley?

Btw, (still searching) but whats the resistance supposed to be for Cam,Crank and Crank Ref supposed to be?

 

Crank REF checks out with my Oscilliscope, as well I checked the condensor at work. That's fine aswell.

I believe my issue is my crank POS sensor.

Thread to Crank POS Sensor findings

Just to update...Feels lonely inside here