Well, I had to take a service manager and a Nissan "Master Technician" on rides to prove that it was hesitating. Technician said he’d never seen anything like it and he’d have to contact engineers at Nissan N.A. I Dropped my Max off yesterday morning.

They called yesterday afternoon, said it was fixed- they had to reprogram the ECM because it was leaning out the fuel/air mixture too much.

So, did it work? Not sure yet. The hesitation came back a few minutes into my drive, but at a lower (about 3000) RPM. It was a lot more subtle. As I drove 30 min. home, however, the problem stopped happening. So, the jury’s still out- it might be gone for good, it might not.

BUT… here’s the juicy part- my car is running like NEVER before. It feels like there’s 10-15 more HP at least! Throttle response is quicker and better than ever, and it feels like I can get to 60 a LOT quicker. More power is available in every gear. My guess is that they fattened up the fuel curves and gave me a richer mixture altogether- but I’m no expert. My butt dyno is very, very, very happy though!!

So, my dilemma is that even if the hesitation is still there a little, do I want to bring it back in and risk having them undo whatever they did to my ECM? (not to mention what a huge PITA it’s getting to be, etc, etc)

 

Describe the "hesitation". Is it a surge/cut in throttle when you slightly let off the gas pedal and then reapply pressure?

If so, it sounds like you might be talking about the FUEL-CUT issue MOST of us 5-speeds have. Supposedly, getting the ECU reprogrammed helps, but doesn't quite fix it.

 

This hesitation was different. Happened between 3500-4500 RPM in every gear. (Mostly right at 4k-4100) First noticed at highways speeds when it started getting hot. As the days got hotter, it got worse.

It happens/happened when steadily accelerating (slowly) to the RPM range or cruising at 85 on the free way (holding throttle steady.) NOT when letting off the gas.

It felt like a cylinder was missing on and off- very jerky sort of stuttering feel.

The Nissan tech I took for a ride was familiar with the fuel-cut issue and said it felt different. Also, that issue should have been resolved before my AE was built.

There’s the possibility that this is very similar to the fuel cut issue, however. Someone said when they fixed the original fuel cut, they just moved it to a different RPM range. Sounds like Nissan logic to me.

 

Some other possibilities could be a bad coil(hard to trouble-shoot which is the culprit) or possibly an overly sensitive knock sensor. I would suspect it because you said it acts up more when it's hot and the ECU was leaning out the fuel. Keep us posted.