Runing lean problem

**LHRxXD3adXx** · 12-12-2014

So ive been fighting this issues since i got my car done its a 98 gtp ls32 swap. I keep having the runing lean code come up over and over agian. I did have a few leaks on my headers and stuff so i got that fixed and my fuel mileage was at 11mpg before and now at 15mpg so i fixed something lol. But its still runs lean. I made a smoke machine to do a smoke test and there are no more leaks so my last thought is that my o2 censors are bad. I have three on there but only use two. There is one right behind bank 2 on my headers that i use and the one at the U bend that i also use. The extra is behind the after the cat. Whats an easy way to tell if they are bad. I have a great scan tool with live data and stuff that can help.

**Fivefingerdeathpunch** · 12-12-2014

So a P0171 code???

What do your fuel trims look like?

And you can just watch the o2 mv on he scanner, look at them switch up and down and up and down. Anywhere from .100 to .900 give or take, should just swing up and down all the time. If it's hanging up and staying at 400-600 all the time, it's a bad sensor.

**LHRxXD3adXx** · 12-12-2014

Ok thanks before i fixed the few leaks short terms were ar trying to add 16 and 17. Now with those things fixed short term was better i cant remember the numbers. But loong term is still trying to add 16s all across. Sorry im still learning this stuff thats all i remember

**LHRxXD3adXx** · 12-12-2014

And yes p0171

**LHRxXD3adXx** · 12-12-2014

Ok so after looking at them the one right of the headers goes up and down form .2 .8 .6 and stuff but the other one just stays from.6 to .7 so is that a bad sensor?

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**Scottydoggs** · 12-12-2014

you link was jacked up. the rear o2 does about nothing on a 98. the up stream should be dancing up and down rather fast. im not sure what o2 is what in your pick.

**LHRxXD3adXx** · 12-12-2014

Ok so the one right of. The headers is fine it bounces up and down. No leaks that i could find with a home made smoke machine. Where to next im out of ideas

**Scottydoggs** · 12-12-2014

you say l32 swap, what blower is on the car now? gen 3 or a gen 5? did you hook up the pcv to the TB?

**Fivefingerdeathpunch** · 12-12-2014

Need more info on the car, what mods, what was done with the motor swap.

Bigger injectors or changes in maf sensors are huge causes to random lean conditions. If the tune isnt right, you are just chasing your tail.

**LHRxXD3adXx** · 12-12-2014

Ok here is the list. Ls32 full swap. Big daddy headers. Still have a u bend. 3 inch full exhaust with flowmasters. Northstart throttle body. Stock injectors. 3.4 pulley. Cold air intake. 1.9 rockers. Colder plugs and thats it i think

**Scottydoggs** · 12-12-2014

you tuned at all? you cant just toss a N* and maf on. and you need to run the pcv to the TB as well.

**LHRxXD3adXx** · 12-12-2014

I bought it with the northstar so it should be tuned to it and what do u mean by having the pcv to the TB. I am going to tune tonight and see if it helps

**Scottydoggs** · 12-12-2014

http://www.grandprixforums.net/threa...cover-breather! a gen 5 blower has a line from the blower to the TB. the N* has a place for it to go already iirc. but some dont know and use a filter/breather on the valve cover

**Fivefingerdeathpunch** · 12-12-2014

Never assume anything, the tb and maf are not stock so you can't just trust that they are tuned correctly.

I'd throw the N* in the trash anyway, you are not even close to outflowing the stock throttle body and maf sensor yet. Pop a stock maf table back in the car and the problem might just go away.

**LHRxXD3adXx** · 12-12-2014

Ok well ill have a look at those tables. My friends is got hp tuners and is going to take a look at it today

**LHRxXD3adXx** · 12-12-2014

Ok so my northstar and the supercharger had that blocked off. But i can just take it off and run a hose. So why do i need to do this? I understood that it will make the pcv valve function which explains why i had negative pressure in my valve covers and i ended up using a breather on my oil cap.

**Scottydoggs** · 12-12-2014

so the pcv works as it should. the breather on the v/c is allowing un metered air in the engine.

**LHRxXD3adXx** · 12-12-2014

So that could be causing my lean then right?

**Scottydoggs** · 12-12-2014

it could.

its possible the tune is off as well because of it.

you dont really need that n*. get an adapter plate to get the l67 TB back on there and drop the stock maf tables in your bin file. hook up the pcv like the how to says, and you should be running better.