Need Advice on Passing Emissions
 

First off, I must say I know little to nothing about cars. I learned how to drive in a 1991 Nissan 240sx and have been a fan of Nissan ever since. I was always intrigued by the Skyline, especially since it wasn't available in the US for many years until recently. I learned about the Infiniti G35 and how it is basically the Skyline but marketed for the US and set my eyes on it. When I got in an accident that totaled my 2010 Nissan Altima I took the insurance check and the opportunity to buy myself my "dream car."

I found a good deal on a heavily modified 2005 G35 out of state (rural Washington, I'm from Portland Oregon) and after meeting the guy and test driving it, I feel in love and bought it on the spot. When I attempted to register it though, I was unable to pass emissions due to a O2 sensor heater, so I continued to drive it for a year under the previous owners registration until I could no longer drive it legally. At this point I had to garage it as the driver side window motor is burnt out and it was starting to grow mold inside the car. It sat in the garage for about a year until I ran my 2002 Infiniti i35 into the ground. Now it was time to unleash the beast as I was able to convince my wife that getting my G35 legal was going to be better/cheaper than trying to fix the i35 which had countless issues.

I took my G35 to a mechanic specializing in Japanese cars to get a OBD reading and he said he couldn't read it since the battery had recently been replaced and no codes were showing on his scanner. I then went and got a trip permit so that I could at least drive it legally until I could get the codes to pop up, but nothing was showing on my Bluetooth OBD2 scanner (Kiwi 2 + Torque) so I took it to DEQ (required emissions testing for Portland metro) to expedite the process. This time they told me the Catalyst was unsupported and that the previous owner may have tuned it to bypass it.

I then took it back to the mechanic whom referred me to another mechanic whom was supposed to be able to help me. He took a look under the hood and told me that the Catalyst was hollowed out and that he wouldn't be able to work on it, I wouldn't be able to pass DEQ, and that it would be a costly fix. He said my options were to register it outside the Portland metro area somehow, or to replace the Catalytic Converters which he estimated to be about $1500.

So now I am unsure what to do as I know nothing about cars and have basically a 7k lb paperweight in my garage. I don't know a ton about what all was done to the car other than the previous owner said it had 339 HP, it is lowered, has a strut bar and I think straight pipe exhaust, but that is all I know forsure. I will try and find the Craigslist post from the previous owner as I'm pretty sure I saved it somewhere.

Any advice on this situation would be greatly appreciated. Thanks!
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Your exhaust sensors are not sending the expected signal to the ECU and it shows up as an error.
Three possible solutions. Only the first is legal.
1) Change the exhaust back to stock.
2) Set up a forwarding mail box in a location that does not require emmision testing and use that address to register the vehicle. If you have already failed the test in that state it may show up in their records.
3) There are modified 02 sensors that only send the expected signal. Thats all I know about them. Do a search.

New Cats aren't $1500 unless your state requires CARB approved ones like California does. You can buy used OEM ones on Ebay for like $300 for a pair if you decide to stick with OEM, but there's a risk that they might not be great.

Its very likely that the previous owner had it tuned and since they didn't have emissions testing had the rear O2's deleted in the tune to keep the check engine light off. If that's the case no matter what you do to the exhaust it will NEVER pass emissions. You will need to have it reflashed again with Uprev to turn the O2's back on.

​I'd prefer to do it legally if possible it seems like a hassle to have to change addresses and I'm not sure how that would affect other things like insurance etc. i.e. if I'd have to change all my addresses to the new one.

As far as changing the exhaust back to stock, do you mean the cats or the whole exhaust system? I did some research yesterday and while I initially thought I had a straight pipe exhaust, I don't think this is the case as I believe I still have cats. The second mechanic said I had hollow cats, not that they were missing. I'm also curious how he can tell they were hollowed just from looking down from the hood, or if he just saw they were aftermarket and assumed.

Honestly, I don't know exactly what I have other than it's heavily modified and I can't drive it in its current state. I can take pictures of that would help though and I'm doing my best to learn as much as I can on my own.
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I think he was referring to new OEM ones from Infiniti, which when I looked last night were $738 each. If I were to buy OEM I would do as suggested and buy used and swap them out just to pass DEQ as others have suggested in other threads.

​​​​​​​Would another option may be to buy high-flow cats and have them instead of hollow/no cats, that way I get a balance of performance and ability to pass emissions? Would high flow cats be able to pass in my state and is this a viable/preferable option for someone woth no experience and little knowledge of cars? Again, I bought this car to learn and I am willing, but I also do need it to be street legal.

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​​​​​​I can almost guarantee this is the case. I have never seen a CEL on my car even though Torque shows Oxygen Sensors and Heater Unready, and Catalyst unavailable. DEQ guys also said it was likely tuned by previous owner to bypass Cat's since there was the discrepancy on their report. If I have it reflashed is it possible to save/export the current configuration and the reload it after the test? Should I retune it if not or keep it stock?

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What is likely the best (legal) to getting getting it registered? Looks like I need some used OEM cats or some high-flows that can pass (little unsure on this). Something to rise the car and the tools to remove and replace the cats (breaker bar, 1/2 extensions etc from watching YouTube, not sure on other tools). I also need to l likely get reflashed to stock it appears though I concerned this may not even be an option with all the mods done to it as it might be throwing codes like crazy from reading other threads/forums with users with similar issues.

​​​​​​​Thanks everyone for all the help with this issue, I really do appreciate it.

Not sure if this is allowed but I didn't see anything against it in the rules I'm going to attempt to bump my post as I need to resolve this issue asap since it took 24 hours to approve my post.

I also added some pictures to my album in case it helps anyone assist me. It looks to me like the cat is stock and I'm not sure how the last mechanic was able to tell it was hollowed either.

It also looks to me like I have a cat back exhaust with a y-pipe, not a straight pipe like I thought. I have pics as well as I could take of the underneath of my car in my album above.

Also please see my replies in the post right above this one as I don't want them to buried. Thanks!

^^ He may have just sniffed the exhaust and been able to tell the stock-appearing cats weren't doing anything.

He literally popped the hood and said "yeah, this is too modified for me to work on" then shined his lights to where the cats would be and said they were hollowed, lol. Also when I bought the car I asked the guy if it would pass DEQ and he didn't mention anything about modified/missing cats and said it would pass.

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Update:
I talked to the guys over at Performance Rage Engineers in Portland and they said that they should be able to help me to get it tuned while being able to pass DEQ and that that would be likely the best option as it would throw codes if other parts weren't stock, so it sounds like that's what I'm going to do. They also said they should be able to help me figure out the status of the Cat's, so here's to hoping that it all works out and I'll be able to drive it again soon.

I'm still a little confused on how the licensing works for tuning. I was quoted $700 total for the license ($300) and the time on the Dyno ($400). Does that mean that if I want to tune it again I will just need to pay for the Dyno (since I've already paid for the license), but that I will have to take it back there and only there since they hold the license?

They are proposing performance dyno tuning which isn't what you need. Your not looking for performance gains your looking to pass an emmisions test. Your problem is simply that something has been changed in the exhaust system that is preventing the 02 sensors in the system from sending the expected voltage signals to the cars ECU. It could be a lot of things that are impossible to identify by posting. My best advise is to find a shop that specializes in fixing emmisions issues to pass the state test. Worse case would be that you need new cats and sensors but it could be a lot less.

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Ok, I feel as though I'm getting conflicting information and it is likely due to what you said, trying to diagnose the issue by posting.

DEQ and some members here have suggested that it's an issue with the ECU and that no matter what I do to the car as far as exhaust/cats/sensor it wont pass. While others seem to think it's an issue with the cat's exhaust etc. I guess I'm just confused and frustrated as I haven't really been able to find anyone willing to help me as far as mechanics go, and these were the first guys to offer hope that I will be able to pass DEQ (and retain performance). But I agree that I don't want to spend money for a tune if that's not the issue, or if it won't actually get me to pass.

I guess I will try and find a shop that specializes in emissions like you said, maybe see if DEQ can refer me somewhere. I just have a feeling they're going to tell me I need to take it to a performance specialist and try to pawn me off on someone else.

It could be either of those things, that's what makes it complicated. It could be cheap and simple, or it could be extremely expensive. People are just suggesting likely possibilities they have experienced or other issues that would produce the same symptoms. In the end, somebody with the car needs to sit down and troubleshoot the issue. You could even be failing inspection for several different reasons.

If the exhaust smells like an old muscle car or a go-kart, your cats are hollowed out or not working. You'll need new cats.

To pass inspection in the NE you can't have a check engine light, and the OBDII scanner needs to be able to communicate with the onboard computer to verify that your computer isn't flashed to hide the light, amongst other things. According to a quick google search the code "Catalyst is unsupported" could also mean your ECU isn't communicating with the scanner, which would fail you and could also make poor or shady mechanics certain they need to replace your cats.

If you knew what mods were on the motor, you would know if it were safe to switch back to a stock ECU, which would only cost you a couple hundred dollars as long as you source your own parts and DIY. You could also pay close to $1000 for an UpRev dyno tune. The guy who does the tune should be able to figure out any engine or emission problems easily if he's experienced.

Ok that makes sense, hope I wasn't coming off hostile or ungrateful as I really do appreciate everyone's help here and I'm already learning a ton which was the goal in getting the car in the first place.

The car doesn't smell like that, I know the smell you're talking about and the exhaust smell's like a normal exhaust would, to me at least.

I'm starting to be able to figure out what's done just by looking at the pics I took and comparing them to the service manual as well as googling images of the stock parts. I know for sure I have a Kinetix Intake Manifold connected to a Fujita air intake (keen eye for the obvious, lool). I believe I have a dual cat-back exhaust with a y-pipe (ISR brand?) when looking at my pictures in my album, and the cat's look pretty stock to me compared to what's on eBay for OEM used as well as compared to aftermarket. Obviously, I can't tell if they're hollowed or not without taking them out, which is why I was confused that the one mechanic could. Personally, I think he was just lazy and/or didn't want to work on my car as it was "too modified". The other parts I'm trying to tell based off of the stickers (lol) and am not sure exactly what else is done without getting deeper under the hood/car. If I had that original craigslist post that would have helped but evidently I didn't save it and relied on the link which expires after 6 months I believe.

What I'm unsure of is if any of those mods would cause CEL lights if I reflashed to stock which is only $100 or if I should really pay to get it tuned and if that will fix my issues or just be an extra expense when what I really needed was OEM parts etc.

I also signed up for a free CarFax which told me the last service done to it was replacing a O2 sensor back in '15, so I am going to assume it has them just potentially disabled since that was done about a year before I got it and the guy sounded like he'd had it garaged for a bit.

I guess what I need to figure out what my best course of action is and cheapest <legal> potential path to getting it registered. I'm not sure if I should take it to the tuners first and have them try and help me, or if I should try and find a mechanic that will be able to tell me what the status of the cats/sensors are. The former seems to be the most reliable but costly, the latter has been fruitless for me so far as I am having a hard time finding anyone that will work on it.

If they smell fine and the car runs well, the cats are probably fine, so that's good news.

I looked at your picture, and didn't see any serious performance mods which would make your engine any different to work on than anything else - the Kinetix manifold looks (and is) expensive but it's not really a big power adder, and the intakes are known to lose power on these forums compared to the stock ones. I have one just like it, makes cool noises :)

What I did notice is that you've got a non-revup engine from a 2003-2004 G35 swapped in, which MIGHT be causing issues with your ECU if it wasn't done properly.

You might be able to just swap in a used ECU of the correct engine and transmission combo if your problem is indeed with the computer, and get it reflashed at the dealer.

Did you get the PO's facebook/phone number? Why don't you call him up and ask him if he knows anything about this? Tell him you've already bought the car and you're just trying to figure out what's going on and he might stop lying to you.

Thanks for taking the time to check out my pics, it definitely helps having someone help me figure out what's going on under there. I have no idea how you or especially I would have been able to tell the engine was swapped. Can you elaborate on how you know for my own learning, and why somone would have done this?

So if that's the case I just need to fund a used OEM ECU, swap it out and have it reflashed to stock? Would my previous ECU still have the previous tune so that I could swap it back? And is this something a noob like me could/should do?

I still have his girlfriend's phone number and I could certainly try and reach out to them. I don't believe he lied to me about anything personally, I think that the one mechanic that told me the cat's were hollow was full of it. I'll send them a text and see if there is any way he'd be willing to help me figure out what all was done to it, thanks again for the help!

I'm not a tuner or a mechanic, but to my understanding replacing your ECU would remove that as a possible issue, you could keep the old ECU if you wanted the tune. It might be buried under a panel or two, but it should be literally a plug and play removal you can do at the parking lot of the dealership. Search "nicoclub g35 coupe FSM" for some good reading for learning more about your new car! If you want to own it for a reasonable cost you should get used to diagnosing and solving small problems on your own and performing basic maintenance on your own if you don't already.

The non-revup engine has variable valve timing on the intake valves only, which is visible on the front cover of the motor (Google Images: VQ35 revup vs non revup). They make less power and don't rev as high, but have more torque down low and don't have the fatal oil consumption issues the later revup engines had, which is probably why yours has been replaced. I wouldn't worry about it, although I would pull the spark plugs, change the oil, and monitor oil consumption for awhile as these cars all burn some oil.