so the whole gapping the plugs to .40 wasnt the solution ?

 

It worked for all of a few drives, basically up until the last month I have ran the same tune and hardware for the last 2 years and never had an issue. There have been no misfires since the new plugs and gapping, however the fuel cut reared its ugly head. I really don't know anymore, this car has been a basket case which I guess comes at the price of having a pristine 36,000 mile ng900. I am going to try the simple things first and see how those go but it is frustrating that the misfires/fuel cut seem to come at random because you can do a dozen WOT pulls and be fine and then one will have those issues come up.

 

k again sounds like the same issue i had and jp is still having.... if you reset the ecu it goes away untill adaption has finished then it comes back...so every time you fix somthing that you are sure is the reason for this missfire or fuelcut and reset the ecu you are sure you nailed it then two days later bam it happends again... sounds like you have the same issue as i do although yours sounds a little less severe then mine

 

is it a full fuel cut or is it sort of a weird fluttering?

 

like this?



its unlikely its the fuel pump unless your having a partial failure, since the stock pump can handle stage 4+ tunes ie 250-270ish whp.

the key is that you say it happens when you roll into 2nd

long story short, swap the DI with a known good/or new. this is very similar to a high rpm misfire/flutter i chased on an old 9000 which wound up being a mildly flay DI when pushed hard. basically the spark was blowing out when it came on too hard.

 

Ah, that is great to know. I think I will find a T7 DI for the sake of reliability and give that a try, then I will look towards the other options I have which I hope to avoid. Thanks again, I will let you know how this turns out!

 

convert to a t7 bpc while your at it?

 

Haha, I know T7 BPCs are cheaper and more reliable but I am not really interested in modding the car anymore as I will be giving the car to my younger brother this summer and I don't want to put any more of my own money in it (already have $12,000+ in it).

 

let me know how the DI work as i have a similar problem.....................i say this, but then tonight the car ran FLAWLESSLY........grrrrr.....turbo cars are so moody

 

I will update for sure, I think I will go for a black T7 DIC for the longer spark duration and more powerful spark plus the reliability over the T5 cassette.

 

And you're not worried about the difference in Knock detection between the two DI's?

 

I haven't found any information against moving to a T7 DIC, this includes no one with blown-up engines or any difference in performance. From what I have gathered, a T7 DI has lower voltage to detect knock slightly later than a T5 DI but those who run them on a T5 motor find that knock levels and knock detection are fully functional and the motor adapts to changes in octane and environmental conditions just as efficiently as a T5 DI.

I may just go with another T5 DIC just to keep in line with factory hardware but I was debating the T7 DIC on a T5 engine due to what seems like advantages in spark duration which I heard allows for smoother operation and better spark for tuned cars.

 

I bought a known working DIC from Mockba and threw that on yesterday to see if it worked. Well, today I rolled into second and fuel cut hit on/off/on/off/on/off until I let off the gas. To recap:

-All new sensors (o2 sensors, coolant temp, blah blah blah)

-Vacuum lines checked and are all connected to their respective locations with no split lines

-New Saab OEM fuel pump installed 6,000 miles ago

-Known working DIC installed


I am not sure what to try next, I will get a new BPC as well because the car feels like it is overshooting slightly so that might be part of the problem. Is there anything else I should look into?

TIA


Edit: forgot to reiterate that the car runs as normal at anything under 5/6 throttle, not even the slightest hickup.

 

BPC sounds like a good idea to swap out too.

Also, ever think of a weakening wastegate? Causing too much boost for a short period of time, fuel cut etc....but that would only really solve the fuel cut, no missfires.

 

I think I am only experiencing fuel cut since you can see the light poofs of black smoke when this happens before I lift off the throttle. Good idea on the waste gate, I had chadwick build my T28 from a turbo he had but I swapped my wastegate from my OEM T25 (30,000 miles on it) before installation. I will double check my base boost as well to rule that out.

have you talked to john about this

I will PM you regarding that.

 

have you talked to john about this

 

Any chance its the change in elevation and you need a remap?

Idk whats the elevation difference between CA and wherever you were on the east coast but is it sizable enough to cause an issue?

I still think its the stock fuel pump try to keep up with your injectors and tune.

 

I was 100 ft up from sea level in Connecticut and am probably 10ft at most above sea level in CA so that wouldn't be an issue. I have always had that thought in the back of my mind about the fuel pump but I have talked to a number of people who are running similar or higher power levels than I am with the stock fuel pump and they have had no issues for the years they have used that setup.

Leaving the fuel pump and DIC aside, what could cause fuel cut?

 

Leaving the fuel pump and DIC aside, what could cause fuel cut?

Other then overboost? the rev limiter.

Thats all I can think of.

Unless...this is a bit of a stretch.....the roll over fuel shut off valve?

 

Kink at the fuel filter location?

Wastegate adjustment?



Your problem and FiveIron seem to be having the same issue though.

Both are tuned by the same tuner.

 

Make sure you're smoking a cigarette while doing this
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oh you'll be fine!

 

Make sure you're smoking a cigarette while doing this

No way dude.... lung cancer is serious business.

Christian, come by some time if you wanna try a new DI around the block and see if it's any different.

Best,
Drew

 

Now, is the fuel cut (like STOPS the car) or is it a misfire that is just a bit intrusive and stops you from revving smoothly?

 

It is almost definately fuel cut because the car stops accelerating completely, sorry for the confusion as I did some research on the difference between fuel cut and misfires and had a hard time differentiating.

 

Keep in mind there also a difference in "stops accelerating completely", and fuel cut.

During fuel cut, not only do you stop accelerating, you also get a harsh bucking. Got that too?

Just trying to figure out if you acutally are experiencing fuel cut or something else.

 

Yup, harsh bucking. What happens is that you roll to WOT once it shifts to second and as soon as it hits full boost, it cuts out and starts bucking until I let off the throttle.

My apologies for the confusion.

 

Any chance your FPR got knocked loose? It did travel across the US in a rather harsh ride from the looks of it... Just a thought.

 

It looks like there are some commonalities here; quite a number of JZW tuned guys are all here for the same problem. Hmmm. I just ordered a T5 BPC since I am not in the mood to modify the car's wiring for the T7 BPC, past that I will have no choice but to look into the tune and fuel pump.

 

Sounds like you guys actually are hitting over boost fuel cut I however am not. My car does it with that feature turned off

 

I would stop throwing money at the cars and get John involved as this "sounds" like issues with the tune. Does anyone have access to T5 suite that can flash another tune into one of the ecu's just to see if this bucking goes away, doesn't have to be the perfect tune for a test?

 

I will have this side covered this weekend or next by someone involved in the making of T5suite, then I will go from there. It also worries me that features such as adaptation and overboost fuel cut are being turned off in our tunes (mine at least) and only found out about these features recently. Past that, I am still going to try a BPC from another member to rule that out and go from there.

Thanks everyone for working together on this issue, keep it coming!

 

I have made up my mind that I will go after a few more parts related possibilities before looking into the tune since that could get a bit more complicated.

 

So let me get this straight. The issue you two have is wot full boost it bucks then the car goes still. Now this buck is it like a face smack the steering wheel or just a hasitation?

 

Nearly face smack, it cuts then power starts coming back then it bucks again in rapid succession. I hooked a temporary boost gauge up a year ago or so and was hitting a spike of 20 lbs.

 

At what paid boost is this happening? What rpm. What map sensor are you running