[07Versa6MT]

So for a while, any time i was WOT, i would get random stumbling, no misfires just at WOT, and once in a while a little stumble. I had never suspected injectors but realized they can start to get bad at my mileage. This morning coincidentally had a really hard start. Wouldn't start for two tries, then fired up fine. Now it stumbles like a whore in low gears at WOT, below 2300 RPM. I may just have gotten a bad tank of gas, but at my mileage (330 000 KM) it's reasonable to believe injectors are dirty or just worn out. Also doesn't pull nearly as hard as it used to.

What do you think?

I'm not going to use injector cleaner, if they're bad, they're bad and i will replace them.

 

[Versa12]

Any CEL's?

I would throw a couple bottles of HEET and fuel injector in the gas tank and see what that does. If the gas is bad you should see an improvement. If the injectors are dirty you also should see an improvement. Pretty cheap way to see what is causing the problem.

 

[07Versa6MT]

No codes. I'll just drive it normally and use up the tank i have then see what happens.

Update: Well, my diagnosis is injectors or a fuel supply issue at this point. The fact that it occurs only during cold soak to me indicates dirty injectors with a bad spray pattern, requiring warm engine for vaporization, or wrong fuel pressure. The weird thing is that high RPM running is fine, it doesn't pull as hard as before this problem but doesn't stumble whatsoever. No misfires... If i go to a higher gear and revs are 2300 or less and i mash it, it will stumble all over the place, but not misfire. Not a single misfire code. It's not WOT switch related since it will happen at just off WOT. It took me forever today to start it, this battery really proved itself. Key cycling to build fuel pressure didn't work. Just kept cranking, with breaks in between to be easier on the starter. I'll crank and crank and then one cycle it'll fire up no problem, which to me indicates vaporization problem due to bad spray pattern. It will display the same stumbling and huge lag when revving, if i mash it it'll stumble to just over 2500 then run fine from there. Idle quality is fine.

I've known about the FPR recall for a while, but those were the kind of thing that present problems shortly after being driven off the lot due to some assembly issue. This is completely random. Unfortunately these have a dumb returnless system, which means no test port on the rail. There has to be one at the tank on the pump.

 

[fonque]

The in tank fuel pressure regulator in first gen versas are known to go bad. They cause very hard starts and stumbling in certain conditions. There should be some threads floating around the NICO forum about it. There is even a video on you tube of the replacement.

 

[07Versa6MT]

Thanks chief.

Update: A tank of high octane and a can of Seafoam (in fuel) has improved the problem, no hard starts yet. Still not going to rule out bad FPR, but it did help with the low end stumbling too. I bought the high octane for more pre-mixed additives and general higher quality for all you people wondering why, and Seafoam is my favorite product for general engine decarbonization or cleaning. I have a set of reconditioned injectors on the way. Whenever you order "remanufactured" injectors, understand that it only consists of ultrasonic cleaning, new filter and o-rings, and flow matching (the last one is hopefully).

I was going to get 550cc injectors in preparation for my rear mount turbo but i can't really afford that yet.