NGK coppers with 7 heat range.

Modified by articzap at 4:17 PM 7/21/2008

Is it definatley spark blowing out?

Even so it was fuel cutting it'd continue to do it above 4k. Thats the weird part. Its only down low.

A/F looks fine too.

I'm pretty sure I know the cause; I noticed it the other day when I was tuning with a wideband. The "why", however, is still a mystery. Anyway, at that particular rpm range and that particular load, the engine runs pig rich, like 9:1 AFR. For some reason, the target pullswidths Nissan put in that particular section of the fuel map are huge, and the throttle tip-in enrichment as you get on the gas certainly wouldn't help things.

You wouldn't happen to have aftermarket cams would you? My theory is that because of the differences in the cams yadda, yadda [insert a bunch of cam design jargon here], perhaps the secondary butterflies are openning at the wrong time to suit the cams. And maybe need to open sooner because they're restricting the higher flow capabilities of the cams.

Of course, that theory goes out the window if you've got stock bumpsticks and I'm probably wrong anyway.

This seems most likely than my previous theory, now that I think about it.
Thoughts?

Modified by Buddyworm at 9:46 PM 7/13/2008

Keith
'84 S12 Turbo; Ca-det powered
'95 Maxima A32
http://www.cardomain.com/id/1984rps12

Have you checked the fault codes articzap?

Definatley check the continuity of the ignitor....

I searched through the FSM and couldn't find the test. Does anyone happen to know the page its on? I wonder if I'm having a similiar problem. My narrow band O2 sensor is reading 14.2-14.6. I'm starting to think its running a lot richer then that. I wish I had a way to test it though. I'll pull fault codes in a few minutes.

I'm just more and more confused with everything I check being in perfect condition. How do you set the TPS in case that could bumped during install? I don't know if that would cause this issue or not.

The SOHC ka is not the same.

- ARC smic
- Centerforce Stage II clutch
- 3" Megan Racing 02 housing
- 3" Megan Racing downpipe/test pipe
- 3" RSR Ex-Mag cat-back (sounds awesome)
- Removed A/C, P/S, and stock fan
- HKS air filter

Best 1/4 mile... 14.2 @96 mph 2.0 60ft. (stock turbo@12psi, open diff)

shooting for mid-low 13s with stock 370's, hybrid t2/t3, n60 maf and chipped ecu.

My Apexi turbo timer is showing around .6-.7 volts during those RPMs.

I will find the pages you need for the continuity check and the tps setting tonight and let you know..

Out of curiosity, does it happen more often at WOT or does it have the issue regardless of position?

I just lost to a third gen Camaro because I couldn't accelerate at a light. Had to play to catch up and was pulling on him, it was just to late.

Thank you very much meminto. If theres anything you need, please let me know.

Power Transistor (ignitor) EF&EC 125

Idle Switch - EF&EC 100

Throttle Position Sensor - EF&EC 98

You don't actually adjust the TPS, you adjust the idle switch...

This is from the euro manual which is the most common one floating around...

Now to add to possible light to the problem. After work I'll test the power transitor. But on my way to work today I was getting spark blow out around -8 inHg. Then when I'd let off the gas it would almost die all the way out. I then got it up to 4k and floored it. It had spark blowout for a few seconds then proceeded to pull like normal when in boost above 4k.

I'm starting to think its a going power transitor, which I'll check when I get home or I have and over fueling issue causing the plugs to foul out in the low RPM's and causing the spark blow out because of an over rich condition.

I'm going to assume this condition is caused by the Walbro 255 lph pushing to much volume through the injectors. Does anyone else think I should try pulling some fuel out of the mix with SAFC?

The fuel pressure is regulated, so the pump couldn't be pushing to much volume as such...

Actually how healthy are your injectors?

Wouldn't hurt to try. I've got my afc set all in the negative range...like -8 and -9 throughout.....because it was running pig rich. Found this out when I got it dyno tuned a couple of years ago. before the tune it would cut out at wot ONLY in 4th and 5th gear at 4000k-4500k. After the tune the afr's are where they should be, and it hasn't cut out like that again. Still not sure if my stock fpr is to blame because of the walbro 255

drftsilva, I would like to borrow a wideband for tuning but I need to get a bung weld it in my test pipe then. Stock injectors are 370cc. I doubt fuel was getting pushed past them, I just think to much fuel is being let through when they are open.

My lo map is 0

My hi maps are..........

800 rpms: 0
1600: 0
2200: 0
2800: -9
3400: -9
3800: -10
4600: -10
5200: -9
5800: -8
6400: -8
7000: -10
7600: -10

I took about 10% out with SAFC and it is indeed running a lot better but I'm still having issues.

I believe I have stumbled on to the reason why so many guys running Walbros run stupid rich. Its all in the bypass fitting.

When I was having problems I had my stock Synapse FPR and my Walbro. In order to get the car to run I needed roughly 38 psi of fuel pressure. I would also get horrible spark blow out, terrible gas mileage and tons upon tons of black smoke. I began by removing fuel with my SAFC. That alone worked wonders but never got it right. Besides, trying to fix an issue with SAFC is just a horrible band aid solution. I knew the problem was fuel now though. So I read through my Synapse directions, and sure enough it says that if you run a Walbro 255, you need to change the bypass fitting to a 2.5mm. So today I got home and began to tear into it. What ***** it is to get the FPR off without taking off the rail. Stupid firewalls. Well I change the fitting and put it back together. First thing I did was start it up and go check my fuel pressure. At idle I was getting 23 psi of fuel pressure. Seemed low but I revved the motor a bit and it shot right up to 38-40 psi. Before when I revved the motor it would shoot to 80 psi. I figured alright the fuel pressure is low, but lets take it out and see if it exhibits the same symptoms as before. I drove around until the car warmed up. The true test was about to come. I put it in first and got the car above 4k and floored it. Still pulled very hard up top, if not harder. My O2 volts were hovering right around .5-.65. Respectable voltage. I then proceeded to give it the true test. At about 10 mph I put it in 2nd gear. I gave it a nice 50% throttle pull. I came up with 7 psi and had just a bit of hesitation. No big deal, the plugs are probably just fooled. Tried it again and all of my issues were gone. The car runs nearly perfect now. All thats left to do is to install drftsilva's wideband and get this beast tuned for 14 psi.

Well your thinking to yourself, I have similar issues but I run a NISMO FPR. If you're running a NISMO FPR with a Walbro 255, you may have something thats not solvable unless you can change the bypass fittings, which I doubt you can, or drill out the bypass to allow more fuel to get past.

Or just buy a real FPR.

Where can you buy the fittings at?

On the Synapse FPR, theres to vacuum ports. One for the FMU and one for the static fuel pressure. I had it hooked up to the FMU port. D'oh. I hooked it up properly and good lord. That fixed my fuel pressure issue too, FYI.

I'm now making 12 psi on the stock wastegate and holding 12psi till around 6500 RPM-7000 RPM. I'm so happy that its finally working properly. 14-16 PSI here I come.