Acceleration issues on SR20DE block with Neo VVL head

[nicoxis]

Need some help guys...

I have a Nissan Primera (also known as Infiniti G20). Originally it had a standard SR20DE but I've done couple of mods to it, Neo VVL head swap, high performance 4-2-1 extractor (speed daddy), Fujitsubo High flow exhaust and a JWT Pop charger.

Bellow are some pictures of the head swap process, which my mechanic did.





















My issue is that acceleration acts weird, specially when cold. Just pushing gently on the gas pedal it starts accelerating and then it decelerates (no matter if I push it further down).

The problem is reduced when the engine gains temperature (harder to notice), and it only seems to disappears when going WOT.

I've looked for vacuum issues but found nothing. I'm thinking it may be a problem with my injectors being dirty or not mounted correctly, but that's just guessing on my part (I'm a car newbie).

Any ideas on what else I should check for? O2 sensor maybe? maybe I'm running lean?

Thanks in advance!

[nicoxis]

anyone ?

[06_blkout]

I wish I could help but I don't know anything about the SR20

[nicoxis]

I wish I could help but I don't know anything about the SR20

thanks for answering, SR20 aside, what would you think if this was happening to any car ?

[pressafoot]

tps sensor definitely is sticking or not working.. happen to me lots of times

[nicoxis]

checked TPS sensor and it's working properly...

It has another symptom, the fuel line that goes from the filter to the fuel rail keeps loosing or braking.... I think I have a pressure variation that is causing the hesitation and causing my fuel line problems.

Would a fuel pressure regulator fix an issue like this?

[pressafoot]

Whoa wtf !!! Please thoroughly describe and explain the hose situation cause this dont sound right

[nicoxis]

No prob, one day I started feeling a huge gas smell while driving I found that the fuel hose was massively leaking (it was broken).

I replaced it and though I just had a faulty hose. Some days later I felt a gas smell again, this time no broken hose, it just got loose and was leaking through the end of it (I thought, maybe I didn't tighten the hose clamp enough). So I went ahead and tighten it.

After a few days the smell came back again. And this is were I began to think that my hesitation issue could be related to fuel pressure. Why? because if pressure is going up and down causing my acceleration to stall and go up again that could translate into some kind of pulling of that fuel hose leading to the issues mentioned above.

I don't have any startup issues, performance and fuel consumption seems good. I don't know where else to look for...

Would a fuel pressure regulator fix my problem (assuming that my theory is right)?

[pressafoot]

Damn like that just sounds sooooo weird...fuel pressure regulators help buy a really cheap one with a gauge and see what happens but if you are going rich then the car would get sluggish and you would smell gas..... know what it might be though? Your ground wire on the maf maybe you need to reground it.. that might possibly be the problem... check it out

[nicoxis]

I'll get the pressure regulator and see what happens, thanks

[nicoxis]

installed fuel regulator, it alleviated the issue, but it's still there :/ I'm getting a Wideband to see what's going on

[nicoxis]

Just to close the loop on this one, the issue ended up being the original ECU not able to handle the mods. So I installed a new ECU with new map and timing along with a SAFC2 and wideband to fine tune.

Car is working like a charm now!

I'm looking into NIStune now, do you guy know what's the average price for that?