Write-Up: Northstar Throttle Body Install

https://www.dropbox.com/s/lo8xruz9xvm5mml/112314.csv?dl=0 - LOG

https://www.dropbox.com/s/yt3qwl7n4indkma/96v6.1.bin?dl=0 - BIN WITH PE ENABLE SET TO 100% TPS

Yeah dude IMO get a new o2 (pre-cat upstream). I'd recommend Denso like zzp says but I've used the usual Bosch without any problems in the past. The downstream one doesn't do anything useful for tuning. An unaltered car can generally slide by ok with a poor o2 sensor but when you have to tune in a new maf sensor and it's not giving good info, you really have nothing. Emissions will let that sensor nearly go dead before it says something's wrong and the PCM doesn't have any really solid way to verify that sensor so it's considered to be a 'trusted' sensor. And it looks like the knock is similar or even attenuated without power enrichment so whatever the PCM is trying to do in fuel trims is not helping.
Just to verify, were you basically KR-free before the maf change or was there anything else changed?

I was pretty much KR free before the new throttle body/MAF. I could stay WOT from 0 all the way to 100+ without seeing a blip, but if I gave it a little gas on the highway in 4th I would see a degree or two. Do you have a part number (front and rear) for the Denso sensors?

Do you think I should just pick up an LQ4 MAF and gut the 96-99 N* MAF since there's tables readily available for it and more people have more experience with it? I'd rather not spend the money on one if I don't have to, especially if I'm going to be getting new O2 sensors.

You have the northstar maf setup with the plastic maf housing that bolts to the tb right? Are you using the maf sensor that came in that housing or did you swap in your L67 maf sensor? I believe it fits in that housing the same. No matter what it's not gonna be dead nuts perfect but I'd think you should be able to use your original maf sensor in that housing with the factory maf cal table and run ok. You need a good o2 to confirm anything one way or another but i'd try that.
I don't remember how much different that earlier northstar maf housing is than the original L67 throttle body maf area but I assume it should only make a small difference. If porting that area completely out of an L67 throttle body doesn't do enough to the maf sensor flow to require a maf calibration tune then I reckon the northstar housing won't.

I'm using the sensor that came with it, but I can try swapping in my original sensor and flashing back to the tune I was running right before I installed the new one. I was also surprised by how much it started knocking.

Grabbed a Denso 234-4012, will be here Tuesday. Will spray the existing one with PB tomorrow and Tuesday to make life easier.

Does anyone think I should throw in my OEM MAF (same p/n as the N*) and flash the tune I had before installing the N* to see what happens?

The sensor that came along with the northstar setup has the same part number as your oem one? I don't know if I ever looked into that.

turtleman wrote:

The sensor that came along with the northstar setup has the same part number as your oem one? I don't know if I ever looked into that.

Yep. Parts stores don't show it but they are indeed the same exact sensor (96-98 L67 = 96-99 N*) The reason the usually don't show up together is because most places want you to buy the whole plastic housing with the MAF for the N* while they only want you to get the sensor for the L67. I can even take a picture of the 2 side by side so you can see that they are the exact same ones if you would like.

New sensor is in, going to get a good scan whenever I go back out. Should I re-enable the stock PE settings, or leave them at 100%?

Well I found a guy on GP forums with pretty much exactly the same issue as me, only he has the 72mm zzp stage 2 body. Another guy said just to bump the stock tables up 25% and start from there. Wouldn't you know it? Knock is mostly gone.

deekster_caddy wrote:

Will it start if you unplug the MAF sensor? Is the IAC opening?
Also, you may need to adjust the idle set screw. The IAC should technically take care of it but on mine I had to increase the stop a bit to get the idle smoothed out.

Would the idle set screw on a northstar TB set the stage for lean fuel trims at zero throttle? should it be backed out a bit to adjust for the 3800 idle and cruise?
Seeing lean trims at 0 throttle and cannot find a vac leak. Scraping for anything else I can check.

When I did mine I just had to start/drive it a few times and it learned itself. Fuel trims were still a bit off until I dicked with them, but it finally started to idle/run right after a couple days.