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Mystery Leak? Lean condition

nice smoker you made. id just rtv that b back on.

and your tuner is using what tuner? you need tiny tuner to kill the cat test in a 01-03 car. and to use that you need dhp tuner.
 


Scottydoggs said:
nice smoker you made. id just rtv that b back on.

and your tuner is using what tuner? you need tiny tuner to kill the cat test in a 01-03 car. and to use that you need dhp tuner.
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Thanks Scotty! I was pretty impressed with the operation. Worked just as well as some shop grade smokers I've got to use before!

And the throttle body is pretty bent, but luckily my buddy has a spare L67 tb, so we'll just slap that on.

As far as I know, I'm 90 percent he's using hptuners. hopefully that can do the trick. I'm borrowing my friend's wide band so I can get it done right. I'm crossing my fingers!
 
your car a 01-03? if not its gonna do that bs over fueling crap on ya for sure.

and the tb has to be for your year group or the maf wont fit right, or with the tuner you could swap the maf file from what ever year maf your using too i suppose if its not the right year.
 
Scottydoggs said:
your car a 01-03? if not its gonna do that bs over fueling crap on ya for sure.

and the tb has to be for your year group or the maf wont fit right, or with the tuner you could swap the maf file from what ever year maf your using too i suppose if its not the right year.
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I knew about the tb issue, and fortunately it's from a 01.

Please explain on the over fueling. I'm afraid I know very little about how the rear o2 sensor affects the fuel trims. I was always told it didn't affect then? And I've got an 02.
 
Thanks Scotty. I think that the way its setup now, the rear o2 isn't causing many issues other than the mil. Everyone there was talking about removing the o2 and their fuel trims maxing. Mine don't, and I still have the rear o2 installed.
 


if its setting the cel its over fueling most likely. id try a o2 sim, one of them set ups that moves the o2 out of the pipe some. if it turns off the cel you should be good.

pick these things up and you should be ok.

 
I actually ran this spacer for a while and it worked, the only issue was that it collected condensation and rusted out the sensor in like 200 miles and shorted the heater wire. I think it has to do with the angle the o2 is at on the speed daddy headers. Anything I can do to fix that?
 
you have a per and post cat o2, we are talking about the post cat one where the flange to the cat back is. sim goes there.

the up stream you can move lower into the dp, like the goose neck area.
 


IIrc the way to correct the cat diagnostics issue is to set the codes to report but not set the mil. If it’s setting the mil, the pcm knows the rear O2 isn’t working and it won’t dump fuel.
 
Thanks iceman. Can that be done with hp tuners? Or would I need something else? I think I'll try putting the spacer on again just temporarily.
 
yea DHP and HPT can change the way codes are reported.. IIRC there is three ways to set it, normal, Do Not Report, and Disable. If you set it to normal it will set the light and show the code. If you set it to Do Not Report it will have the code but not set the light. If you set it to disable the code basically gets removed. If you remove the code the PCM wont know that the rear O2 isnt working so it will start dumping fuel to "test" the cat. And it will just keep doing it. But if you set it to not report the PCM will know that there is an issue but it wont set the light.
 
Thanks for the input! Tune didn't really do a ton. It's at 0 ltft and 0stft idle and goes to -7%ltft with gas. Found an exhaust leak on the header, so I'm going to try that. Ended up keeping the stock tb and just patching the leak. Runs much better! At least now I know it isn't a vacuum leak!
 


So the saga continues! :th_laugh-lol3: I ended up replacing the ECT sensor, thermostat, and IAT with no change.

Found an exhaust leak, so I swapped from my sd header gaskets to the mil oem acdelco gaskets (sprayed with copper gasket adhesive), used copper rtv on the crossover pipe and upgraded to stepped 2.25" band clamps, and exhaust leak is gone.

Also went ahead and deleted my egr since I just got the code removed with the tune. Much more room now!

Broke a spark plug wire in the process, so I got a replacement set from the junkyard (8mm ultra low resistance brand from summit racing).

I'm thinking the old spark plug wires were higher resistance than the new ones because the power and throttle response made my car an entirely different ride!

However, then I got a code for the bank 1 o2 sensor and found that the fastener had come loose and melted the plug, so for a quick fix, I used a good plug and spliced the wires.... yes, I know, not the best practice. Got a new acdelco sensor on the way.

Even with it spliced for now though, I'm getting much better mpg and throttle response. No more P0420 now too since I used the spark arrester spacer trick.

So to close, I'm at 0% stft and ltft idle and deceleration, and around -7% ltft on acceleration. Hopefully the new o2 sensor helps? If anyone has anything else for me to try, I'd be very open to suggestions!
 
Installed the new o2 sensor. No change whatsoever. I'm going to perform another leak test for vacuum leaks, and one on the exhaust just to be safe. I think this might just be a stock issue. I've never seen long term fuel trims under acceleration posted by anyone before. If anyone comes across this, I'd be really curious to see what a "normal" stock long term fuel trim graph over normal driving conditions looks like on a base n/a grand prix.
 
Well, the plot thickens... turns out I have a vacuum leak again! lol didn't think that could happen with negative fuel trims.... anyways, figured I'd post a really quick video of me doing the smoke test and where it's leaking from. I'll definitely be going with a new throttle body. This one is just too warped. Definitely just using rtv and no gasket this time though.

Good news is I used the same method on my exhaust and there are no leaks! (finally)


Still have to take out the o2 spacer. Still not sure how that works, but maybe it'll help. Looks like I have my weekend cut out for me...


 
Well Scotty, I'm glad I listened to you on this. Throttle body was indeed warped, but not as much as I thought it was! Verified with smoke machine and she's all good now! (and I don't have to pay for a tune!)

Best news of all though, I was still uneasy about the fuel pressure, so I picked up a acdelco one from the junkyard, popped it on, and wala! Fuel pressure around 48psi key on engine off and 57psi with engine running and vacuum removed!! Now my fuel trims are right around zero in park both ltft and stft! I go slightly positive (+2% on acceleration and -.75% on deceleration!!)

I think the coolest thing about this is that I found out some new stuff. So running a 10psi fuel pressure increase will boost your fuel trims by about -10%ltft, and that an overbored engine doesn't need a tune if run stock, and that a overbored engine doesn't affect fuel trims when run stock! Kind of cool stuff!

Anyways, now on to my pesky coolant leak.... :th_shakinghead1:
 
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