Failed inspection..

[t.mcginley.jr]

Finally got my car registered today, got my license plates, put em on and went to get inspected.

I live in NJ so they have emissions testing. The last time my car was inspected (and passed) was in 2006 from the previous owner. Since then I did a ton of engine work and replaced the whole exhaust system (it has new Magnaflow cats installed) and the AIV's are intact.

So I failed the idle emission test horribly, but passed the high idle (2000rpm) test no problem. Here's the numbers:

HC (hydrocarbons): 460 ppm / 220 allowed
CO (carbon monoxide): 7.84 % / 1.20 allowed

So after looking these things up, I'm probably running too rich at idle. After I got the car home I heard some gurgling noise on the top of the engine, I have to investigate that. But I might end up doing that vacuum trick just to get it passed inspection. You remove the vacuum line going to the fuel damper and it drops your HC and CO readings ALOT. Any thoughts?

[AZhitman]

When you fail because of high HC, it means the engine isn't burning the fuel, and it's also washing / diluting your oil. Some common causes are spark plugs, spark plug wires, misadjusted timing or vacuum leaks.

When you fail because your CO is too high, the fuel / air ratio is way off and incomplete combustion of the air/fuel mixture. A CO failure will always be rooted in the fuel injection system. CO failures are not fixed with fresh plugs.

I think spending some time with the emissions section of the FSM is a better idea - Here ya go: http://www.nicoclub.com/FSM/300zx/1990/

[t.mcginley.jr]

I'm wondering if it's related to the gurgling noise I'm hearing from the top of the engine. I removed the throttle cover but still can't locate where it was coming from and I don't see any fluid (fuel or otherwise). I have a feeling I won't know until I pull the plenum off.

As for injectors and spark plugs, they are all brand new. Would a slightly pinched injector o-ring cause high readings like that?

[AZhitman]

Definitely could, if it's leaking fuel. Check out the homepage article on Deatschwerks - we talk about this issue.

I'm inclined to think the "gurgling" might be coolant-related. Do a quick top-off with the bleeder screw loosened and see if that eliminates the fluid sound.

[t.mcginley.jr]

Ok so after getting a few days to work on the car...

The #6 injector o-ring WAS pinched. When I looked down around the plenum, the fuel rail itself was dry except around the #6 injector it was wet. So I got a new o-ring on it and put everything back together. I ran it around for a few minutes and came back to pull the codes. Came back with codes 13, 34, and 42. Since then, I've taken care of the code 34 with a new knock sensor harness (the KS is brand new OEM) and also code 42 with a new OEM fuel temp sensor. I reset the ecu and drove around for a few minutes again. Now the only code left is 13, coolant temp sensor. A new one is coming via USPS today so I'll get it installed tomorrow.

Would a leaking injector o-ring, coupled with those 3 error codes, cause my high HC and CO readings? I don't remember the numbers at the moment but I know I was WELL over the max allowable for both.

[t.mcginley.jr]

Also, after getting rid of code 34 and 42, I drove to the gas station, fueled up, and then it wouldn't start. Took about 10 minutes before it finally started. Would the bad coolant temp sensor cause that?

[Ace2cool]

Definitely could be the CTS. And the temp sensor combined with the fuel temp sensor could definitely cause the HC fails. An excess of fuel can also clog the cats and keep them from burning efficiently, which could give you high CO readings.

The pinched O-ring alone though would give you high HC readings.

[t.mcginley.jr]

Would the pinched O-ring indirectly lead to high CO readings also? AZhitman mentioned that a CO failure is "always rooted in the fuel injection system".

And now that I think of it, the inspector put the exhaust probe on the drivers side, which had the leaking injector O-ring. I would love to know what the results would have been if he put the probe on the passenger side

[Ace2cool]

Would the pinched O-ring indirectly lead to high CO readings also? AZhitman mentioned that a CO failure is "always rooted in the fuel injection system".

Absolutely. The pinched O-ring would cause excess fuel to transfer directly from the fuel rail to the cylinder, without being controlled by the duty cycle of the injector.

[t.mcginley.jr]

Great thanks guys, I'll let you know what happens after I go for my re-test (after installing the new CTS of course)

[t.mcginley.jr]

So I still failed inspection, just not as bad as the first time. Still high HC and CO at idle.

First time the idle numbers were:

HC: 460 ppm / 220 allowable
CO: 7.84 % / 1.20 allowable

This time the idle numbers were:

HC: 229 ppm / 220 allowable
CO: 2.52 % / 1.20 allowable

So I'm getting much closer, but the CO still seems to be the main problem. As a recap, fuel injectors, spark plugs, injector connectors, fuel lines, fuel filter, fuel temp sensor, coolant temp sensor, knock sensor, and KS harness are ALL new (OEM).

I did notice after getting it home though that the short piece of fuel hose going to the fuel dampener is bulging. The hose is brand new and it IS injection hose. Would the fuel dampener or fuel pressure regulator being bad cause higher fuel pressure and therefore high CO readings??

[Ace2cool]

Couldn't hurt to do a pressure test.

If it's in spec though, you've most likely got a bad cat, or something else is wrong with the injectors (possibly another pinched ring?) Not likely though.

[t.mcginley.jr]

I think I forgot to mention that both cats are less than a year old, they are Magnaflows. I know I read that a vacuum leak can cause high CO readings but if it was only a vacuum leak, wouldn't my HC be OK and only CO would be high?