Hey guys,

As the title states I own a 1998 Nissan Primera SRI P11 that comes with the SR20DE engine, making 131PS in this version.

I purchased the car recently and it has around 140k KM's, it had been well maintained with regular oil changes and always used good quality fuel, and is overall in very good shape.

Now, the previous owner, when I bought the car, had informed of this issue and I myself saw it happening when I test drove the thing, thinking that it would be something simple to fix later down the road (silly me!). In normal driving, it accelerates regularly and climbs along the revs normally and gets up to speed pretty quickly, although a friend has told me that it still felt down on power.

The big issue is that under hard acceleration, in every gear (neutral included), as soon as it gets to 2500RPM it hesitates wildly, almost like it's being blocked by something and climbs slowly to 5000RPM at which point it "releases" itself and blasts normally to 7000RPM with full power. It's almost like it's being choked for those 2500 RPM's in the middle.

Now, let's get to the gigantic list of things that I have already tried and have NOT worked:

- New spark plugs;

- New spark plug wires;

- New distributor and new cam position sensor;

- New TPS;

- Decatted (in case the old cats were clogged, they were not);

- New O2 sensor;

- New Knock sensor;

- New IACV;

- Adjusted timing back and forth (no changes);

- Some people advised me that it could be the fuel pump but I had a friend drive the car with my ear against the fuel tank under the seat and it sounded very normal to me, with increasing power as the car accelerated;

- Cleaned and sanded every single ground on the car;

- New battery.

Now, at this point, I have searched every single forum page with people describing this hesitation and tried every single one of the fixes they suggested to no avail. I am running out of ideas and I am desperate for a solution.

One thing that I noticed when I was driving the car around with it plugged into the OBD2 scanner is that on the O2 sensor voltage gauge, under WOT, the voltage dropped to 0 while under regular acceleration it kept scanning and kept the voltage under acceptable levels. This led me to believe that it was all the O2 sensor's fault but I put a brand new OEM sensor in and nothing has changed.

There are also no codes being showed in the scanner, and no lights on the dash.

I have a brand new ECU that I borrowed from a friend to try and plug in to see if it would help and I'm also going to change the fuel filter just in case but I have serious doubts that it would be a filter causing this issue due to the consistency of the hesitation in the rev range, always at 2500 RPM.

I hope there are some bright minds in this subreddit that can help a desperate and very confused Nissan owner.