got the car from a guy that let it sit for approx 5yrs... had to replaced the trans (ZF6 conversion thanks to everyone here!!! )

Now I went to get it tagged and was told I need an emissions test... it passed HC and NOx no problem, but the CO% was nearly double whats allowed.

I've researched a little bit (and searched here) and found this..


So would it make sense that I can replace the o2 sensor, clean the TB, reset the IAC and TPS and then it should pass? (assuming that the airfilter etc. is ok)

 

More than likely the 02 sensor. I wouldn't worry about the IAC or TPS.

 

Scanning it might help, but knowing the actual test numbers would provide some insight, so if you have them, post them. Where the HC's were in relation to the CO can point to possible solutions.

 

25/25 Test (25mph constant)

HC - 103 (137 allowed)
CO% - 1.10 (.87 allowed)
NO - 797 (956 allowed)
CO + CO2 % - 14.6


50/15 Test (idle?)

HC - 132 (140 allowed)
CO% - 1.53 (.79 allowed!)
NO - 819 (1046 allowed)
CO + CO2 % - 14.9

Car was fully warmed up (drove it around for about an hour or more, freeway/city mix)... fresh gas.

 

My 87 failed the test the first time I did it this year. Replaced the O2 sensor and it passed with flying colours

 

How does it run? It looks a little rich. You may want to tune it up if hasn't been done recenrly. Any MIL problems? Note: The NOx may come up as the mixture (CO/HC) clears out, due to the increased combustion temp.

 

MIL?

How many o2 sensors do I have? I know about 1 on the drivers side downpipe.. is there one on the passengar side?

I put in new plugs and wires last year right before the trans went, so I think they should be ok...

I guess it runs ok, this is my first vette and I put *maybe* 15mi on it before the old trans went out, so I have nothing to compare it to.

 

Looking at the numbers, I'd be inclined to believe that the O2 is sensing a lean condition causing the ECM to add more fuel than it needs, but you might want to make sure that the air filter isn't plugged up. You can confirm what the O2 is sensing with a scanner or by grounding the diagnostic test terminals with the engine running. If the Check Engine Light is flashing really fast, wait until it slows down signalling closed loop operation. Then if it's on more than it's off, the O2 is sensing a lean condition (and if it's off more than it's on, it's sensing a rich condition). Assuming it's reading lean, you'll need to look for anything that might be letting in air after the MAF. That includes the connector to the Throttle Body, Plenum & Runner Leaks, vacuum and exhuast leaks (did you remove the headers to install the tranny?), leaking air pump check valves at the headers or an air pump solenoid that is directing air to the headers after it's gone closed loop. There of course remains a possibility that the MAF is sensing more air than is flowing through it or that the O2 is faulty, but I would want to rule out all the other things first.

 

Thanks for the input guys... I never removed the headers, just the Y-pipe from the 3-bolt flange back. Headers stayed on the car.

I replaced the o2 sensor (Bosch oem replacement), cleaned up the throttle body, installed new wires (checked the plugs they were ok), cleaned out between the radiator and condensor, (?) man it was full of leaves and stuff... checked the filter/intake path to the TB it was ok, checked the PCV valve, it was ok, ran another can of seafoam thru the intake with minimal smoking, put some Lucas injector cleaner in the tank...

Had a preliminary test today just to check ... and it got worse.


Today was quite a bit hotter, but here are my numbers now...

HC - 148 and 162 (wayyy worse than before)
CO% - 1.48 and 1.77 (higher too)
NO - 528 and 591 (this went down quite a bit)


This seems to be indicating a rich condition, right? Do you think its possible the new O2 sensor is bad?

Hoses looked good all around... possible bad EGR? Maybe a leaky injector?

 

Man i feel sorry for u, look at my mods it passed emmision on first try, call me and let me see what can i do for u, actually the guy did emmission on my car i know him little bit but probably he will hook u up, when he did run on my car he ran hard very hard so that it will burn all carbon and help out produce less carbon. so goodluck and give me a call lets see what can i do for ya.

sami 404 822 8070

 

thanks for the offer! I may be calling you soon..


also *bump* for the weekday crew to give suggestions.

 

You might try using the Diagnostics I previously posted to see if the O2 is reading Rich or Lean. My guess (and you might as well use Ouija Board until you know) is that it's sensing a lean condition and it's dumping fuel that it doesn't need making it extremely rich. If so, you need to hunt around and find out where the extra air is coming from. On the other hand - if it's neither rich nor lean - ie; grounding the diagnostic link has the Check Engine Light flashing the same on/off pattern during Closed Loop operation - then it needs a new CAT. Knowing what the signal is makes finding the problem a lot easier - without knowing, it's a crapshoot.

 

I just had mine e tested today. I was under "hot rod" status. Here's a copy / paste of driveclean where I live
" it will be considered a hot rod if the motor differs from the type that was originally offered by the manufacturer for that particular model year. All hot rods registered as the model year 1999 or earlier will continue to be tested according to 1980 emission standards"

Instead of just testing it "as it sits" I unplugged the ESC wire (brown/black wire by brake booster) so the computer couldn't control the timing and it was just set to the base timing of 6 degrees. It threw a service engine soon light, but disregard that.

Test-----------Limit---------Result
Idle HC---------300-----------23
Idle CO %-------1.5----------0.88
40 kmh HC------242-----------3
40 kmh CO %---1.92---------0.01
40 kmh NOX----2520---------331

I think it would have passed without the disconnection of the ESC connector but just in case I did it anyways.

 

That makes sense.. The problem I have now, which I've been trouble-shooting more than this emssions stuff, is that my check engine light never lights up. I've tried swapping bulbs and it hasnt helped... in fact, I dont think anything on that panel lights up. Soooo, until I get that fixed, I cant use that as a diagnostic tool.

 

Do you have an adjustable fuel pressure regulater?

If so what is it set at?

If you do and it's set for perfomance, can you take it back down to a stock level and after BUMP it back up to your performance setting??

I'm in California and this is what I'm going to do when it's time!

Thanks,Matt

 

I think I'd head to Autozone and see if they can pull codes. The light not coming on bothers me..if you know how to use a digital voltage ohm meter ..the first thing I'd do is check to see if your getting power to the light.

 

If Range and Instant doesn't work either, it's usually the ECM. I have worked on one or two cars where the owner has removed the light after purposely cutting the O2 sensor lead (with the thinking being that Open Loop operation provided better performance). Under that scenario, it isn't going to pass.