I just took my 92 GTA in for smog this morning to get it registered. It has been non-opted and only driven about 300 miles in the last year, 200 of those miles in the last 3 weeks.

Here is the bad:

HC - 15mph/1548rpm: 130ppm (Max allowed is 108ppm)
NO - 15mph/1548rpm: 1766ppm (Max allowed is 767ppm)
NO - 25mph/2011prm: 1058ppm (Max allowed is 706ppm)

Those are the only 3 things I failed. It was sunny and 70 degrees and I let the car idle for 30mins until they pulled it in to put on the smog dyno.

I plan on grabbing a laptop and trying to double check my tune for 128blms at those speeds and rpms. I also plan on running a can of SeaFoam DeepCreep into my engine and possibly changing my spark plugs and o2 sensor although they are pretty new, last couple years/last 5K miles. MY cat is also a brand new 3" highflow CATCO with only about 3K miles on it.

Any tips on what I can do to tweak my tune for passing where I failed? I am running the stock spark tables and everything else as close to stock as possible. About the only things changed in my tune my VE tables and some temperature settings for various things because I run a 180 degree thermostat.

Thanks!!!

Alex

 

Update:

I've ran and entire can of SeaFoam DeepCreep through the intake and it already seems to run smoother and accelerate better. I also cleaned and oiled my K&N.

I bought a new set of AC Delco spark plugs and I'm going to change the oil/filter and tranny fluid/filter. I'm also going to run a can of liquid SeaFoam through my gas tank to clean my injectors and valves a bit more. I also bought a stock 195 degree thermostat I'm going to install so I can set all the temperature settings in my tune back to stock. I'm hoping a higher temp will help my emissions.

I also ordered a new Denso oxygen sensor from CarQuest that will be here Tuesday. It was only $28 with the correct harness connector. I trust Denso MUCH more than Bosch when it comes to consistant o2 readings so I'm going to re-do my entire VE map.

Before tuning I'm going to verify my fuel pressure since I had to replace my fuel pump about 3K miles ago, and test the MAP, IAC, & TPS sensors before re-tuning.

Anything else you guys can suggest based on those smog readings? Honestly I don't even know what affects my NO and HC readings...

Thanks!

 

Make sure your base spark advance set with the distributor isn't set higher than the initial setting in your bin, too much spark advance will boost NOx levels. I'd disconnect the EST connector and check it with a timing light.

I'd pop the distributor cap off and look for corrosion on the terminals and rotor, and disconnect and check the spark wire between the coil and the cap, it can get corroded at the connections.

Paul T.

 

Thanks for the tip! However in CA the smog tech does that as part of the functional inspection and I was watching him and it was set just as it should be. I also leave my base timing stock and make adjustments in my spark maps.

I'll check the cap and rotor and plug wire as you mentioned too. Thanks!

 

I live in Cal and I didn't know they did that, I'm glad you pointed it out so I don't have it bumped up for my next smog check, I'm sure that sets off a red flag for the inspector.

As you probably know the high HC means the engine is probably missing for some reason, likely either weak spark or irregular fuel, for a car that sat that long I'd be worried about the injectors being gummed up a little, try some injector cleaner in your gas (unless the SeaFoam is doing that). If you have any doubts about the injectors, www.witchhunter.com will clean and flow test them for around $18. each, they've done a good job on the injectors I've sent them.

Paul T.

 

Thanks, no I didn't know that high HC's indicated a miss. My fuel injectors are brand new as of only a couple years ago. They are Accel 30lb and were flowed and matched when installed. Yes the can of SeaFoam I am running through my tank will help clean them if they have gummed up in anyway from being parked.

I also noticed that I have an exhaust leak on my passenger side header. Can this cause adverse smog readings? It looks like a real bitch to get in there again.

I only had time today to change my oil/filter, tranny fluid/filter, install the stock temp thermostat, and re-tune for running the stock thermostat.

Tomorrow evening I'll be replacing the spark plugs, cap, and rotor. Tuesday I'll install the new Denso o2 sensor. I also have MSD 8mm spark plug wires that are only a few years old to but I'll check them for burning or bad connections.

Any other suggestions? I really concerned in my NO readings being 1K over max allowed!

 

if u have a bone stock tune for your car id go with that for testing.. swap in the other tune after . testing is done.

 

I've been trying to get my tune as close to stock as possible and it already is.

Besides, I've been passing smog the last 4 times (8yrs) with my same custom tune. That's why I think this time I failed because my tune is just out dated now for having another 50-75K miles on my engine since I last adjusted my VE tables. I could be burning more oil, have different compression, who knows what.

That's also why I'm trying to get some input as to exactly what I can change to help pass in the area I failed. Like should I run leaner that 14.7 at the mph and rpm that I failed NO or what. Stuff like that.

 

High HC's and NOX can be caused by too much spark timing. With the headers the O2 sensor should be a heated unit. Sitting and idling for 30 minutes may have had the cat cooling off and going out. Right before you go in hold the engine RPM high to put some heat back into the system.

An oil change prior to the test also helps with emissions.

Next time through data log during the test. That will show you what areas of the tune are being used for the rollers.

RBob.

 

with NOx that high your EGR might not be functioning. crudded up perhaps the passages in the manifold.

stale fuel won't run well, you mentioned it's been sitting for a while. run it out or "share" it with another vehicle and get some good fresh 91 octane in there.

i'm not a fan of idling forever before a test. a simple 15 minute average drive should be all the heating up it needs. by idling for so long (and with the stock fan turn-on points on these cars) you can actually be taking the engine temps up 20-30* higher than otherwise which can of course contribute to NOx a bit. Setting the fan on/off points lower (say, 205 on, 202 off) may help. I've done this on my 91, and really like the results. Sorry, can't remember exact values I used off the top of my head. If you start causing pre-ignition due to hotspots in the chamber, well, then your smog test is going to be a loss. :P are the knock retard routines still in effect on your tune?

hope some of this was helpful!

 

AHHHHH!!!!! THAT'S WHAT IT WAS!!!!

The heated oxygen sensor!!! I've been meaning to install one for the last 4 years, lol! The lats time I passed the guy had to run it 3 times to get enough heat! I remeber now!!!!!!!!!!!!

I just ordered one, see this thread of mine:

https://www.thirdgen.org/forums/tech...10-heated.html