Hi,
I have an 85 corvette with 69,000 mi. and have owned this car for many years without any problems. The car has been well maintained.
Today I went to NJ inspection for the 2nd time for high HC emissions.
The 1st time it failed for HC 1823 pass 220 - CO 0.02 pass 1.20 at idle
At high idle it easily passed with HC 43
Since then I have changed plugs cap and rotor, cleaned T.B replaced MAF sensor O2 sensor CTS and CSI switch. I have also checked for vacuum leaks and checked Timing
When I returned for reinspection the numbers were the same and failed again.
Can anyone help, is there something I am overlooking, what else should I check, what are some of the probable causes?
Anything that would put me in the right direction would be really appreciated.
Thank You.

 

Since it is over 25 years old why not register it as an Historic Vehicle. You'll get the QQ plates and be exempt from inspection.

 

Are you saying that it failed at IDLE only?

if that is the case, look at the idle circuit and other idle activity...

cold start injector,. and MOST LIKELY, the 8 injectors themselves. Numbers THAT high indicate a very rich condition....

1st, check fuel pressure. and flow. Make sure the regulator is not leaking gas in the vac line...

Next, without testing I can tell you that your fuel injectors are JUNK.
At that age, the stock inj were pretty trashy new, at 25 they are leaking and spraying wet gas and not a mist.

The seals and O-rings harden and leak fuel past. The nozzles clog with varnish from sitting and inactivity and the spray is disrupted to a drip more than a spray. AT speed with more air its less a problem,. at idle its everything.

1st...Ohms test ea inj hot and cold. Post the results. Anything below 12 is toast, 16 ish normal.

Next, call Jon. At that age I can assure you that your stock multec injectors are bad...so Jon will help you with about a $250-$300 donation and get you some updated injectors that WILL pass. The work is DIY. Easy Saturday job.

BUT,
IIWM, I'd invest the $100 in a set of FSM. Had that been done first you would NOT have wasted $1000 on other unnecessary parts...

There it is....MY best guess. Injectors. You MIGHT try a dose of some GOOD fuel system cleaner but that won't fix cheap injectors with bad seals and O-rings...it may help with the gum and varnish.

IMO, its pointless to get a "classic" exemption. The car is STILL not running right. Smog test DO tell you that you have problems. They may be un-fun and inconvenient but they DO point out the FACT that your engine is NOT right.

Good luck

and DO get your FSM. Money well spent. FleaBay has them by the truck load.

 

I didn't tell him not to fix it. And getting QQ plates is not pointless around here. Getting historic plates in NJ will take care of a lot of problems. In NJ, you can't drive a mile without passing a police car. An out-of-date inspection sticker is what they immediately look for and it is their bread and butter. With QQ plates you're only supposed to drive for exhibition or educational purposes but during the spring, summer and early fall there are cruise-ins practically every night (as a reason why he is driving if pulled over) plus the police don't seem to hassle people with them (with certain towns being the exception)

If he gets the plates, he has the breathing room to get it running right without the fear of getting a ticket every time he leaves the driveway.

 

First thank you for your response.
Yes it failed at idle only that's what has me confused.
What you say about fuel injectors makes a lot of sense and that's what I'll check next.
2 questions though... Is there a tool to remove the clips from the connector on the fuel injector so I can remove it and take an OHM reading and how can I check the cold start valve?
I have thought of QQ plates but I really want to fix the problem before any damage is done and agree with your opinion.