97rebuiltZ28

Good job man!! I’ll homestly miss reading about your adventures everyday lol. Good luck with it and I’m glad that it’s sorted out now.

ridiqls

Haha def will still keep posting. Got a lot to do still

The vents don't work, AC has a major leak somewhere, on the lookout for maybe a RS kit at the junkyard.. still undecided on that.

DrewHMS97SS

The RS kit is pretty cool (I had a '97 RS), but I think you'll have a hard time finding a kit that is in good condition at the junk yard. I had a pretty bad wreck where the whole front end was redone, and the entire body repainted. Even knowing how low the front of the car was, being super cautious in parking lots, and taking all speed bumps and driveways at crazy angles, I still has scuffs on the bottom. That said, most people don't care as much as I did. I can't tell you how many RS cars I have seen on the road with the front effects removed.

Take a look at the RK Sports kit: RK Sport 93-97 Camaro CA-300 Ground Effects Kit - Hawks Third Generation

It looks similar, but you end up with better ground clearance in the front.

ridiqls

Looks like I'm not in the clear yet.. failed smog test. OBD1 is a sniffer test and it passed everything but the Nox is too high. Both at 15 mph and 25mph. Measured at about 9xx when the max is around 750.

Emissions troubleshooting is the worst. Smog tech said it was because the engine is running too hot because the gauge goes up to 3/4 but I know from the scanning and datalogging that it is running at normal operating temps.

I also replaced the EGR valve, put the premium fuel and drove it for about 20 mins before I got to the station.

The previous owner showed me the failed emissions and he also was in the same range for Nox, around 900 something. But he tested with a busted EGR. Apparently replacing the EGR didn't do much.


So, I have a few options. I was told I should try cleaning the EGR lines. I'm not sure how much that will help to be honest, it's over by 200 points.

The other option is to replace the catalytic converter. I hear a rattling right beneath the passenger seat and it rattles at all RPMs. I am not sure if it's the heat shield, the exhaust hitting the cross member, or the catalytic converter is busted inside. But the cat was replaced 4 years ago and the exhaust doesn't have any fumes once the car is warmed up so not sure what's going on there.

Last option is to tune the cooling fans to come on lower to see if it helps with the Nox. Anyone have any experience with that?

Well the final option is to get it "smogged". I just don't like going this route because it's hard to find people.

Anyone who understands the inner workings of emissions.. would love to hear what would possibly cause NOx other than the listed stuff above.


Here's the smog sheet:
Nox is around 1000


I know NOx is a result of high combustion temps.. so possible factors are overheating, EGR which recirculates the nox back into the engine, bad catalytic converter. The fact that NOx levels are higher at 15mph/1800RPM compared to 25mph/2000mph, makes me think it's the cat. As the cat gets warmer it works more effectively? Not sure though

DrewHMS97SS

There are too many pages to go back and read, but did you get a tune done after the rebuild? I though you had gone with a different cam, which could definitely throw off your smog (and how it runs) if not. If you did, I suggest taking the smog info back to the tuner with a recent log of the car running for adjustment.

ridiqls

Actually I decided to go with a stock rebuild so everything on the new engine is stock. And unfortunately, the previous owner's smog results are pretty similar to mine with the old engine, which tells me it's not the engine but something like an accessory or cat.

From what Injuneer told me of the datalog, it seems like AFR isn't much of an issue.

DrewHMS97SS

Did the logs Fred went over show good activity from the O2 sensors? If the operating temp is within expectations, I wouldn't think kicking the fans on early would make that big an impact. Wasn't there something going on with your MAF too? Did that get sorted?

ridiqls

I believe the O2 sensors were good. The MAF was ok, it was just a crack in the intake and a loose connection.

On shoebox's website:
​​​​​​"Too little or no EGR flow can allow combustion temps to get too high during acceleration and load conditions. This could cause:

Spark knock (detonation)
Engine overheating
Emission test failure"

I think the next step is to troubleshoot and test EGR flow. I'm going to have to google how to do this. If the EGR flow is good (and the vacuum holds since it's a new EGR) I can eliminate that as a problem.

Injuneer

The first and second logs were just at idle. The first log showed very good results on the A/F ratio - LTFT's 130 left/128 right. But as I mentioned, it wasn't the same in the second log. As it turned out, the right bank was fairly stable at idle, with the LTFT ranging from 125 to 130.(-2.3% to +1.6%) But the left bank was starting to show instability, with it trending toward the lean side. The LTFT ranged from 128-138.(0% to +7.8%). The results were a little muddled by several instance of revving the engine, which is really pointless, since it doesn't show much of anything with the engine not under load.

Then we got sidetracked on the starter, and I didn't do much more with the second idle data log. The third log was for analysis of the starter problem.

What you need now is a log of the engine operating under load, out on the road. There are 15 more critical LTFT cells, and none of them are used until the engine it under variable load/variable RPM. Running lean helps create NOx in two ways - excess O2 is available to combine with the nitrogen, and lean mixtures burn hotter, providing the heat for the oxygen+nitrogen reaction. But, running lean will usually result in very low HC and CO, and your HC isn't that low.

As I noted before, I really think you need to start a new thread. Leave this one as a record of the rebuild. The new one will cover the operating issues with the engine. As mentioned immediately above, there's just a lot of posts for anyone to go back and review.

ridiqls

Gotcha, okay I'll reply to this under a new thread