mcgee

I have a 92 corvette with a lt1 with a comp cam 224 intake 230 exhaust,24lb injectors,52mm throttle body,adjustable fuel regulator,headers,flow master exhaust and 185 degree fan kit and a chip burned from pcm4less,won't pass emissions HC ppm reading 2521 and co% 3.30! Does anybody have a suggestions?

mustclime

you still have the cats?

mcgee

yes i still have cats

hooked073

you are running way rich chances are you lean it out some you will things down

mcgee

can i lean it out without redoing the chip?

mcgee

today i checked to see if there was any codes found 15 dtc and 13 dtc

hooked073

That would be something your tuner or the guy that burnted could tell you. what is the max co2 reading your state permits

mcgee

1.20

mcgee

my car doesn't get over 170 degrees would that make a difference?

Giamanut

Pull your spark plugs they tell the story. With that HC you have un burnt fuel. The plugs see that fuel burn up close and personal like.
Okay I just failed and then passed smog.
Failed with about the same hc as you.
Engine is brand new overhaul. And here is the story.
The smog place says get some guarantee to pass stuff from autozone and bring it back.
So i go get the stuff and head down the freeway, and as soon as I hit the On ramp I think
wait a minute this is so stupid.
I take it home and pull the plugs which is exactly what you should do!
I have 6 perfect tan colored plugs and 2 black plug so now I know why I am not passing smog. I have 2 cylinders that are not burning all the fuel. The problem even though the valve where adjusted the way most people on the forum say to adjust them I took a 1/4 turn of the valve on just one of those cylinders and took it back in and it passed smog
went home and adjusted all my valve with the car running and it is perfect. and for the record the spin the push rod method of adjusting valve lash is okay only to get the lash roughed in enough to run the engine.

GKK

The HC levels are showing that the engines Air/Fuel ratio is way off and the CO levels show the engine is getting too much Air.

Your engine needs a proper tune.

Giamanut

AFR is not always about tune. Pull the plugs if they all look the same then yes you probably
need to tune but if you have one or two that are black you have incomplete burn in those cylinders! Which could be 1 a bad plug or plug wire or a valve that does not have enough lash both are easy to fix. Plug are always the first place to look and 1 cylinder with incomplete burn will make it fail smog. Spark plugs do not lie.
If all plugs are black your rich
If all plugs have tiny speckles your lean
If all plugs are tan your passing smog
if one or two are black and the rest are tan your tune is good and see above.
You can guess or you can pull your plugs.

Giamanut

To be precise HC levels are showing Exhaust gas at tailpipe has unburnt fuel IE rich. This does not mean AFR is off necessarily. 1 bad spark plug can make the exhaust rich however leaning the AFR will make 7 cylinders lean and still not correct the problem if there is a bad plug or tight valve lash at play. Just saying when OP pulls the plugs you will have enough info to make the call.

GKK

The OP's engine has a lot Against it for passing emissions...

Larger Cam
Larger Fuel Injectors
Larger Throttle Body
Headers
Cooler operating temps

DTC 15 = Coolant sensor low temp. indicated.
DTC 13 = Oxygen sensor circuit wiring/connection.

Definitely, get both trouble codes repaired since they are directly related to the engine failing the emissions test.

Also, if an O2 sensor is installed in the headers, they might be installed too far down from the heads resulting in the inability to correctly read the exhaust.

The C4 Vettes are designed to operate at hotter temps for emission purposes. With HC levels off the chart, I'd take it in for a proper diagnosis to save you time and frustration.





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Kevova

Your code 15 low coolant temp could cause ecm to alter A/F mixture in an attempt cause temp to raise to 185+. The 13 O2 sensor not ready or dead won't let it go into closed loop. Both codes could be / or part of the problem. You need a scanner to see whats going on. You may have to make mods to pass test and undo them afterwards. I am fortunate not to have to go through the nightmare of emission testing

desertmike1

are you running an 160° stat?

bassackwards

You need to get your system to go into closed loop before you can do anything else. The system will never work if the computer is detecting nonfunctioning sensors.

mcgee

I'm running a 160 degree stat and a 185 degree fan switch could that be the cause for code 15?

GKK

Yes, the engine temp is too, cool.

mcgee

ok,thank's for your help!