Just failed smog for the 4th time. I pass every part of the test (idle and 2500rpm test) except that my HC are too high at idle. The requirement is below 100, and it tested at more then double at 220. However, as soon as the rpm is brought up, the HC drops to around 20. I don't remember any of the other numbers, but those were within the limits. I had an exhaust leak before my o2's, right on the EGR flange. I thought this was causing me to fail, so I had to pull the entire header off to get it welded. However, it did nothing to change my results, and now I feel like driving my car off a cliff.

I've spent the last 4 hours searching the forums and google, and from what I can tell, HC being excessive is a result of unburned fuel. Well, my plugs are basically brand new, brand new ICM. Plug wires, cat and opti have less then 20k miles on them. I just cleaned the MAF. Air filter is clean. Mobil 1 oil has maybe 1500 miles on it. The rest of my mods are in the sig. I'm thinking maybe I should pull the injectors and have them tested to see if they are working properly? Where could I get this done at? Also, I read that a fault in the EVAP system could cause high HC at idle? How do I test this....oh and I read somewhere else that a bad PCV valve could cause HC problems, so I'm thinking about replacing that. If anyone has any ideas feel free to chime in. Damn I hate emissions. Thats the price I pay for living in CA I guess.

 

Pull the rails up with the injectors intact, turn the key to "on" to pressure the fuel system, and look for drips from the injectors (Do not turn it to "start" ). A tiny drip will provide a lot of excess fuel at idle, but may become insignificant at higher RPM/engine load.

 

Engine temp is a key to HC emmissions. If you have a 160 thermostat then you will need to program your fans to a higher temperature. You want the engine temp in the 195 range. I have a PCM just for smog that has the fans set higher and it really knocks down the HC. For me it went from 50 to 25 (ppm) by running the engine hotter.

 

Sounds like you did not tune it yourself. Unless you programmer can see your scans, there is no way for them to be dead on a repogram with the mods you have.

It will be as simple as adjusting the computer in the idle area once you know what is going on but you are probably just running a bit rich in that area. This is an extremely simple fix...once you know how rich you are.

 

I had the same symptoms - very high HCs at idle (triple allowable) but the HCs at 2100rpm were fine. The other exhaust gasses were fine on my test as well.

I notice that you have an EWP like I do. I assume this means that you have a double roller timing chain and therefore no crank position sensor and no ability for the computer to detect misfires. This may be the root of your diagnostic problem. It certainly didn't help me any.

A few have suggested looking for an exhaust leak before the front O2s (which you have already dealt with). When I finally decided to pull all the plugs it was obvious that one cylinder was never firing and that was sending unburned fuel (and excess oxygen) past the O2 sensor which was causing the computer to think the engine is lean and add more fuel (creating the high HC condition). Anyway, I also checked each of the plug wires on that bank for resistance and burns and they were all fine as well as doing a compression check on the suspect cylinder and a couple of others for comparison.

I put new TR55 platinums in (after gapping them) and picked up a cylinder immediately. You might also try the water-on-the-header-primary trick to try and isolate a cold (dead) cylinder. I think there are also infra red thermometers that can do a more precise job on that front.

Good luck and let us know what you determine.

 

I can scan the car with Datamaster, is there anything in particular I could look for? I have a feeling there is, I'm just not sure what to look at, or search the forums for...

Another thing I just remembered, my dyno graph shows a 4-5whp dip from my peak of 333whp between 5500 and 5700rpm. Probably unrelated. Another problem I gotta fix though...

Also, whats everyone's opinion on dumping a bunch of alcohol into the gas tank before getting it smogged? Apparently this is supposed to lower HC a lot. I kinda want to do this legit, because I KNOW the hotcam can pass CA emissions, but if worst comes to worst.

I'm gonna pull the fuel rails this weekend. The car has 87k miles, and they are the stock injectors, so there MIGHT be a problem with them. I seafoamed the car pretty good when I bought it, so I thought things would have been taken car of, but maybe it dislodged something.

I have the stock thermostat (195?), and I drove the car for 30 minutes, beating on it, and driving it at low speed in a high gear to get the engine temps up. The gauge was reading 210 when I pulled it up to the shop.

I did get a mail order tune from PCMforless, and it definitely improved the car a lot. I figured the mods I have are pretty common, so I would think that my tune is more dead on then most people. However I do agree that to get maximum performance it does need more then a mail order tune.

I literally just installed brand new NGK spark plugs .50 gap, so I don't think that is the problem. However, just to be safe, I think I'm gonna pull all the plugs again and check them out, and do a compression test at the same time.

 

For the price I would try to Seafoam it first, then change the plugs, and then see if any of the header primary tubes are cool. If any aare cool then you'll be starting into the top end. gl

 

My god man! Just get some adjustments in your idle tune and you are done. Really, I have dealt with this before.

 

The original poster has a 94. They do not have the CKP sensor or misfire detection.


For "dueno".... what did the CO look like at idle? Incomplete combustion due to cold cylinders will drive up both HC and CO.

 

I wish I had written down the exact numbers, but CO was passing at both idle and 2500rpm.

 

Then is sounds like you are dropping raw fuel in the cylinder.

 

There is something else to check, sniff around the drivers side rear wheel well. See if it smells like unburnt fuel a minute or so after you turn the car off. The charcoal canister might be toast, that's what happened on my car when I had a similar scenario.

 

Thanks for the all the help guys, much appreciated. Today is a nice day so I'm gonna start pulling things apart. I'll let you know what I find.

 

Discovered a couple things today. Just because I was under the hood, I tested my fuel pressure and it is within spec. However, the vacuum line going from the FPR to the manifold had a gasoline smell to it, but there was no gas in the line. From what I have read in this thread (https://www.camaroz28.com/forums/sho...issions&page=3) that could definitely increase my HC at idle. Also, I scanned the car with Datamaster and my injector pulse width varies between 2.3-2.5ms at idle, when according to Injuneer's guide (http://members.aol.com/InjuneerZZ/ScanMast.htm#step%208) it should be between 1.4-1.6ms. However, my car idle is raised to 850rpm, so that might be why its higher. Tomarrow I'm gonna pull the fuel rails and check for drips, and then remove the FPR and see how bad its leaking. I think I may have found my problem though with the FPR...we'll see.

 

Update:

Got the fuel rail pulled and checked for leaking injectors, there were none. Some of them appeared a little dirty/greasy around the o rings though.

Pulled the FPR off the back. What a bitch. The torx screw stripped out, so I had to rip out the whole wiring harness and throttle cable assembly so I could pull the fuel rails up and out just so I could take a look at the back of it. Finally got the FPR out, and the vacuum port and line definitely smell like gas, however no sign of liquid gas. Would just purely gasoline vapors cause my HC to more then double the limit (220)?

I think I'm gonna go around and check all my plugs again even though they are brand new. Once I get the new FPR installed and go and get smogged I'll update again. Thanks guys.