Car won't boost past 4000 RPM's

[TS4L]

Hi, I am having problems with my SR20DET boosting past 4000 rpm's. The car starts jerking and sputtering really bad when it revs up to 4 grand. I have checked all my intercooler piping and all the possible places for boost leaks , but no success yet. I have also switched out my Z32 MAFS with a extra Z32 MAFS and it still does the sputtering. Any Idea's would be great please let me know. If it helps here is a list of things that I have:-SR20DET-HKS intercooler and piping- Blitz BOVWalbro 255 Fuel pumpApex-i air intakeZ32 MAFSSAFC 2Bee R* exhaustGreddy 3 inch down pipe I live in Montana so I have a hard time getting any good help so any info anyone might have would help a lot. I am thinking it might be a fuel problem but thought I would ask

[quiksilvia]

my guess would be a vac leak or a boost leak.

[ItzGenX]

Or serious missfiring like I had (only under loads, not rpm specific)

[SpeedRacer1]

Is your ECU tuned for the Z32 MAFS?

This could be something really stupid, once my car wouldnt rev as high as normal, turns out I left the gas cap off. Another time the cold pipe would come loose only at a certain boost and pop off, but whenever I checked everything looked normal.

[quiksilvia]

he said he has the safc 2, so a retune isnt needed

[SRBURG13]

Yeah, I had the exact same problem, and that occurs either when the plug to the MAF is disconnected, or the MAF is on backwards. It won't let you past 4000rpm. My plug came loose at the end of the track. THAT was scary. Anyhow, I'm willing to bet it is something to do with the MAF. Make sure your MAF is on properly, hooked up properly, and that the AFC is set to accept the Z32 MAF.

Good luck.

[TS4L]

Thanks guys I will take a look over everything again and see if any of those suggestions clear up my problem

[runyun]

this is minor..but ck your fuel filter (unless it was already replaced)

[TS4L]

Okay, I have rewired the Z32 MAFS, Changed the fuel filter and went over the settings on the SAFC 2. I have also looked over and double clamped the intercooler piping, but still at 4000 rpm's it sputters and shakes. This is stupid because the car ran great all summer long and then all the sudden this. Please any other suggestions!!!??!!

[912.0turbo]

Mine kind of did the same thing and I looked over the piping and all LOOKED well.So I said screw it one day and took all of the piping off myself and put it back together again(saw some things that looked suspicious but not sure).Now it boosts fine<---knocks on wood

[martin]

How much boost are you running? How are you controlling it?Do you have the stock boost controller?

Interesting that it was fine all summer and it just started doing this... as the temp cooled down maybe? My Rx7 TurboII would do just what you described when the temp dropped significantly... it would build boost much quicker and the fuel cut would keep coming in. With my SR I don't see this problem, but I don't use the stock boost controller... mind you I also have no idea how the SR one works ;-)

Possibly something to think about.

-Martin.

[Cyberkreig]

if it was running fine and now its not I would suspect a blow maf.

[SRBURG13]

Sounds like a MAF problem to me too. Is it violent and WILL NOT let you past 4000rpm?? If so, then yes, it very well could be a blown MAF.

[TS4L]

To answer one set of questions stock Boost and the stock accuator on the turbo. I have two Z32 MAFS's and I have tried both and with both they do the same thing. Maybe I have two bad MAFS's, possible, I will see if I can get a third and try that. I think I am going to replace all my fuel lines from the tank to the filter. But my only problem with that is I have a fuel gauge in the engine bay and at idle it is showing I have 45 psi, but I don't know what the pressure is when boost comes along. Again I really appreciate all the help Thanks

[TS4L]

Ohh yeah I forgot the sputtering and jerking is fairly violent it's like hitting a rev limiter that flucuates back and forth from 4000 to 4600 or so and just will not let the car go beyond the 4600

[TheDonEffect]

I have the same exact problem. Initially I thought I wasn't getting enough fuel so I upgraded the pump. It helped because instead of violent jerks, I just get jerks. Before I had a full on cut, but now it lets me go to 4000+ but then I run into your problem. Is your mixture also very rich as well? Mine is ridiculously rich, I mean it still gets decent gas mileage, but still white vapor out the back, but not really bad when the weather isn't so cold, and no it's not a blown head gasket, compression test is consistent across the board. Anyway, it's not a serious mechanical problem, just one of those annoying, tuning problems. Keep us posted on your progress, I know I want to know what comes of this.

[starfireS14]

Im guessing its hella cold mine does same thing gas line freezes up put some iso heat or something in check plugs o2 sensor and AIV.

[TS4L]

I kept thinking something like this has to be a boost leak so I replaced all my couplings with Samco couplings and took it for a spin. I boosted and the car ran up to 4000 rpm's and started doing the sputtering again but this time all the interior lighting went out tach shut off no heater. So i really got mad and ran the car into boost and watched the revs on the SAFC 2 and i ran the car clear to 7000 rpm's no problem. So I boosted around the back roads for a while because boost in really addictive and then I took the car back home and started checking fuses i blew the ALT 75 amp fuse up by the battery tray. So what causes that???? i must have either a ground problem or the current is arcing somewhere Any help would be great where should I start looking first there are so many possiblities. Thanks

[nissan_s14]

Check all your grounds? From your negative battery cable, to your ground from the lower transmission harness, to the ground for your Z32 MAF.

[TheDonEffect]

So you boosted all the way to 7000 rpms without a problem? Slightly confused, I thought you said the problem was still occuring. Ok, someone mentioned to me that it might be a timing problem, thought about it and it could be, but as these cars are riddled with electrical problems, I'm still leaning towards the grounds or the mafs. <shrug> frustrating isn't it?

[klattr1]

i bet it is a fuse or something. Check one of your main fuses in your engine bay. Like the 100 amp or something. Will your car hookup to the CONSULT at Nissan? This would help with alot of things like mafs voltage and tps voltages to determine what is causing the problem.

[TS4L]

The problem does still occur when I put the ALT 75 amp fuse back in the fuse box up by the battery tray. If that fuse is pulled out or blown up the car runs fine.

[gtune4]

o2 sensor if not proper will cause this.

[NEED4BOOST]

checK your spark plugs and the gap on them!

[TS4L]

Well if anyone is wondering the problem turned out to be a problem with the alternator, the power wire was arcing to the power steering line that runs right under it. Thanks for all the help