It's been quite a while since I've been on here as the G has been nothing short of a terror since March. I think I have the G down to one final issue, but do not know what it is. The G has spent 90% of the last 8 months in a shop, but after a few grand, is mostly drivable again. Let me recap with the short version:

March
Towed to Infiniti, car would not start, security light on solid
Infiniti replaces IPDM, car still will not start

April - September
Towed to independent shop due to Infiniti being unreasonable, still won't start
ECU determined to be shot, ECU replaced, car starts
G continually goes into limp mode when driving, APP replaced 3X, no effect
Limp mode persists, shop determines the ECU harness has a bad pin, fixes with one from Radio Shack, limp mode is gone.

Now the final issue:
Under acceleration (anywhere from 2k to 6k RPM) the G bucks like a bronco under light or heavy acceleration. It essentially just drops out (almost like a fuel cutoff) then comes back within a split second. Sometimes it will be fine, and others it will buck/stutter/drop out pretty wickedly. Bucking happens when the car is cold and warm. No codes are thrown.

In the last couple weeks I've replaced all the following to no avail:

Driver and Passenger Cam Shaft Sensors
Crank Shaft Sensor
MAF Sensor
Spark Plugs
Air Filter

Within the last few months:

ECU
IPDM
APP sensor

The shop has checked the fuel pump, and pressure is perfect.

All reset procedures have been completed multiple times. All parts replaced are OEM.

I've read through every post on all forums at least twice now, and I'm at a loss for what it could be. My next play is to replace the throttle body, but the shop said it tests out.

So, I'm hoping someone on here are can help me out, and finally rid me of the frustration of the last 8 months. I know I'm close to having this worked out, but honestly would like to stop throwing parts at it if I can. Both Infiniti and the indie are stumped.

If you provide a resolution that resolves my bucking problem, I'll PayPal you $50.

Thanks in advance!

David

03 6MT Coupe

 

check ur fluids. motor and trans make sure its at the right level. I know sounds trivial but I had a similar issue and it was becus trans oil was low. this was on a chevy with no dipstick lol

 

Ah, yes. I should have mentioned the following fluids have been replaced in the last 3000 miles:

Engine Oil
MT Fluid
Differential Fluid
Brake fluid (why not?)
Clutch fluid

Thanks!

 

^but the trans fluid is 100% at the right level?

 

I don't have any leaks coming from the tranny, and when I changed the fluid it was up to the proper level. I can check again, but it should be good to go. I can get the G to do the stutter in neutral with the clutch in, so I wouldn't think it's transmission related.

Thanks for the reply!

 

When it cuts out, do your electronics inside the car stay running?

Do the lights turn off, tach drop, etc while it "blips" during acceleration?

 

Everything is perfectly fine with the electronics when the bucking occurs. No other indications of an issue are present besides the engine bucking.

Thanks!

Edit: the tach does visibly stop or very slightly drop when it occurs.

 

Have you checked to make sure your parking brake is down?

 

Yes, parking brake is free. This happens at random, and can go a day or two without issue. If you push the car (4k rpm), it seems to act up more frequently.

Here's a video I took a couple weeks ago of the issue. Video quality is terrible, but you can hear the bucking/jerking pretty well.


Thanks!

 

Maybe knock sensor... I had the same problem... Didn't throw a code or check engine light, so had to get a special code reader and showed a pending code...

 

I have 3 OBDII code readers, and a pending code doesn't show up on any of them. Was this the same case with yours? What reader did you have to buy to determine the code?

Thanks!

 

Came across this from ol trusty eHow:


There are several other symptoms indicative of a knock sensor problem. The vehicle will often shake or vibrate and misfire when the engine is started. The engine may emit strong exhaust and burning smells due to the detonation in the cylinders. Fuel economy is often affected, causing the vehicle to burn more gas than usual and requiring frequent fuel replenishment. Also, your vehicle may display acceleration problems, such as dragging, hesitation or jerking from the engine during speed increases.

Sounds pretty much like what I've got going on. Any clue why this wouldn't throw a CEL? Anyone else change a knock sensor due to these symptoms?

Thanks!

 

The knock sensor shows up as a pending code... It will trigger the check engine light months from the problem occurring... Try taking it to a shop... Only certain code readers will pick up the code

 

I had something similar happen and it was that water got in my ecu idk how and also on the harness and I took it to a shop and they replaced the ecu and a couple of stuff from the harness and it was working fine after that, it was on my sedan, I have never had a problem on my coupe tho

 

The shop doesn't get any pending codes off of it, so perhaps it's a phantom.

ECU is brand new (and dry). I've only put 500 miles on it since it was installed. I think I've had enough ECU issues for one car! Haha

I pulled the trigger on a new knock sensor and harness tonight. Also tossed in a 5/16 plenum spacer while we're at it. I should be able to install both sometime early next week, and will follow up.

Let's keep the suggestions flowing! I do sincerely appreciate the help!