Thread: P11 Power Loss Issues - Need Help/Suggestions

First a little back story on my setup.

2001 P11 G20t
- B14 SE-L (Non-RR) longblock
- All RR accessories, IM, sensors, etc
- SSAC knockoff EM
- WAI w/ cone filter
- Prothane X-member mounts
- Stock ECU
- Manual Trans

Ok, now a little more on my symptoms:

1. While cold, low RPM partial and WOT acceleration feels like a dead spot between 2000-4000 rpm, even in 1st gear. Feels ok, even at WOT, after 4000rpm. I can barely chirp the wheels shifting to 2nd though. Acceleration/Throttle response is best (though not necessarily excellent) while car is cold!!!

2. When hot, low RPM partial and WOT acceleration ranges from dead spot at partial throttle to absolutely ZERO response at WOT. I cannot make it up the ramp at my warehouse without a running start in 1st. If I stop on the hill to open the gate, I cannot make it up the ramp even if WOT in 1st. Car bogs, backfires, and dies.

3. When hot, if idling on flat ground, I can rev the car smoothly up to redline (besides 2000-4000rpm deadspot) with very light throttle. Seemingly no issues. If I smash it to WOT, almost no throttle response. Car barely climbs/crawls up the rpm range until about 4000rpm or so, if it even makes it there. It may accelerate ok after that. Not always.

4. Acceleration while cruising on the freeway SUCKS in 3-4-5. To really get going I sometimes need to shift down to 2nd to get any sort of movement in. Still dead-ish spot from 2000-4000rpm. No bucking or anything at WOT in 3-4-5. Just ZERO acceleration.


Parts changed recently:
- Walbro 255 (new)
- K&N Fuel Filter (new)
- Cap & Rotor (new)
- NGK BKR6E-11 Plugs (new)
- Bosch 15727 o2 Sensors, up and downstream (new)
- OEM MAF (used)
- OEM TPS (used)
- OEM Coolant Temp Sensor (new)
- PCV (new)


Some other bits to note:

Car had really old fuel in it when I bought it. Smelled terrible. Used old fuel pump to pump all the crap gas out, installed Walbro, put new 92-octane gas in.

I cleaned all injectors and they fire all the same. Did not clean fuel lines.

I installed the SSAC and removed the EGR pipe that goes from the SSAC to the EGR valve. Capped off the valve. Left all sensors plugged in, thus my only CEL for EGR. Oh, exhaust leak at gasket between primary and secondary pipes. used the crap gaskets that came with the kit. I have a copper gasket waiting on the side. Also, regrounded upstream o2 at ECU grounds on IM.

Car used to buck like crazy under mid to WOT. Changed out MAF, bucking went away. Acceleration issues were present before AND after MAF swap. Also, regrounded MAF at ECU grounds on IM.

Idle used to suck. Was all over the place. I was actually able to do the idle relearn and car idles nicely, though idle does drop pretty low if I rev it up and let off the throttle. Idle eventually moves back up and settles at a steady 800rpm.

No changes to acceleration patterns after changing out all parts listed above as well!

Had a friend scan it to monitor some settings last night and he said fuel trims were pretty high. Not sure what that means exactly.


Anyways, any suggestions as to what to look at next? Anyone have any similar issues?

The only other things I can think of would be the following:

- Check for vac leaks?
- Compression test?
- Clean TB?
- NEW OEM MAF?
- NEW OEM Distributor (for new CAS)?
- NEW Plug Wires?

ANYTHING ELSE?!?!

Any help/ideas/brainstorming would be greatly appreciated all. Thanks.

Branden
aka hawaiiaNX

Plug wires are a great place to look next.

Other than that, it looks like you've taken care of everything it could be other than the ECU. So, I'd suspect the ECU if the plug wires don't do it. We had another one just like you recently who did everything under the sun, and it ended up being the ECU.

Hey Ben,

Thanks for the quick reply. Just wondering on the ECU (which I thought about, but forgot to list), I would need to reprogram the ECU to the key if I swapped ECU's, correct? And that can only be done at Nissan/Infiniti?

Branden
aka hawaiiaNX

You may want to look at the IACV. The 00+ use a different IACV/AAC than the previous Gen SR's. These use a stepper motor so be sure to check out the FSM for proper trouble shooting. I know my IACV is messed up as its hung up under 2k rpm, once above it closes and the engine runs right. Also your question about the ECM, it doesnt look like it needs to be reprogrammed. Looking at the schematic it shows the ECM looks for a 8-16bit signal from the NATS within a set time frame of the ignition being turned on. Whether this code is unique is unknown to me. I have an 00 p11 I can check this evening to see what this code looks like, but all signs are pointing towards interchangeability.

Interesting points ebinkerd. I would think the IACV wouldn't matter once the throttle plate was open. Just spitballin' here but I would think that, if anything, it would affect really low in the RPM range. My issues come up from about 2000rpm (just roughly after throttle is depressed) up to 4000rpm. Once I hit the higher rpms, throttle response seems to be fairly on point.

As far as the ECU, please let me know if you are able to swap them out without a reprogram. If so, I may shop around for a manual, 32-bit ECU to try.

Thanks for the help and direction!

Branden
aka hawaiiaNX

Mafs are shit across the rr engine line. These symptoms still sound maf to me. Spend the dough and get a new one. Alternatly, I have 4 used ones lying around. Maximas used the same maf whichever generation the 01 falls in is the correct year.
Oh and I have two of those iacv stepper motors around too if you need.

Now that you mention, that does sound like it could be a MAF issue still. I just figured it was doing that before I changed the MAF plus it was bucking under mid to WOT. After changing, it was still weak feeling but no more bucking. Maybe it will be worth trying a brand new MAF. The 22680-2Y001 that covers the 00-01 Maxima and Sentra would, I assume, work for the G as well. Not bad at $90. Maybe I'll bite it and try one.

Thanks canx2k!

branden
aka hawaiiaNX

Try buying just the element.A get away with cheaper.

http://maxima.org/forums/5th-generation-maxima-2000-2003/258878-upgrading-stronger-2k1-maf.html

Already ordered a "Brand New OEM 22680-2Y001 MAF" from Amazon. $87 shipped. Should be here in a week or so. Will report my findings once it's here.

Thanks again!

Branden
aka hawaiiaNX