Searched but found no references to this at all. Any info on this is appreciated.

I need to test this sensor to see if it is working. Do you know of a way to test this? I did not suspect this as my problem but wire broke getting EGR off.

This is the sensor that screws into the base of the EGR. I am changing the egr and the wire broke off of the sensor. Soldered it back on and need to check it. A new one is about $70, tried to buy one with no luck. Napa, Advanced, O'Reillys, and AZ. Only other option is junk yard.

1989 IROC 350 engine, all emissions are connected and SUPPOSED to be working. Runs great with no check engine.

Failed emissions at idle on HC. Top is 120 and I got about 1660. Everything else is good. Last 3 years I got about 116 HC each time. Only thing I changed is the vac hoses on the charcoal canister.

BTW, also changing O2, air filter, water temp sender. Everything else is new. o2 has only 15000 mi but its cheap so changing it. The EGR was old.

 

I have a used one that I would sell if you want to go that route
http://www.mamotorworks.com/corvette...329-11663.html
http://www.chevythunder.com/fuel%20i...temp%20sw..htm

 

Searched google and found the topic in TPI

 

Thanks tuned. I'll just buy a new one.

 

Np

 

Update. Soldered the wire back on and checked it. It works. It'll be sat when the egr comes in - surprised I had to order it.

Have my doubts that the O2, egr, temp sender, injector cleaner, and air filter will bring a 1160 down to 120. Since it was running better than when I was getting a 116. O2 sensor had a nice white powder on it - not tan like plugs usually do. Also tightening intake bolts and checking/changing all vac hoses.

New TPS, wires, cap, and rotor about 2000 miles ago. About 15000 miles back it got completely rebuilt. New injectors, IAC, etc etc. flattops and a small comp cam.

BUT, heads looked good with low miles so I did not rebuild them. I have a new set of World Racing .202 closed chamber heads in the garage I could put on there if it looks like the guides are going out. Just don't need them on there for any other reason. This is a work car DD. I'd have to buy some shorties if I put them on there.

If anyone can think of anything else to change please post. I'm not short of money so I am not trying to half butt this.

 

Checked paper again

HC std 220, idle=1160, 2500rpm=67
CO std 1.20, idle=1.11, 2500rpm=.23

They don't check NOx so no reading. BTW, they did not put on rollers this time. Just plugged in exhaust and ran it.

 

HC is hydrocarbons or liquid carbon, otherwise known as gasoline, that has been vaporized and got through the engine without being oxidized. CO is carbon monoxide or partially oxidized hydrocarbon. HC emissions go high whenever there is any type of misfire. Also, most engines produce some HC emissions as perfect combustion is rare and the engineers count on heat in the exhaust manifolds to burn most HC out of the exhaust. The catalytic converter is intended to oxidize any remaining HC or CO that gets past the manifolds.

A few common causes of high HC are too lean fuel trims causing lean misfire(yes, too little fuel can actually lead to unburned fuel passing through the engine), any type of misfire including a performance cam that affects idle quality. Too much ignition advance cools the exhaust manifolds and allows more HC to pass through. A rich condition or poor tune will cause both CO and HC to go high.

Since you can't adjust fuel trims, you can only be sure that no unmetered air is getting into the engine that would cause a lean idle. You can verify that all sensors, the injectors and the ignition system are working correctly. It sounds like you've been over things pretty thoroughly. Connecting a scan tool to verify that the fuel system is achieving closed loop and that fuel trims are around 128(neutral) would be good. That leaves ignition timing, possibly your cam, and catalyst.

By retarding timing 2-4 degrees, you can reduce HC emissions considerably. Idle quality may suffer and you will want to put it back where it belongs once you pass the test. Making sure that the exhaust manifolds are hot when the car pulls into the test bay is the key. A long drive before hand and running the engine at 1,800 rpm for several seconds right before the test helps. If your cam isn't causing a rough idle, you can probably get around it and pass the test okay. If it's a lumpy cam, you're fighting an uphill battle. Doesn't mean you can't pass, just that you will need alot of catalytic converter do it. The same things that keep the exhaust manifolds hot also keep the catalyst hot. If you can't get through the test by reducing ignition lead and heating up the exhaust, you will need to replace the catalyst.

BTW, many states now only test idle emissions. Seems the expensive wheel dyns they used to use are too expensive to maintain. Aww so sad.

 

Last three inspections are with the engine configured as it is now. The ONLY thing changed since last time is the vac leak fixed on the charcoal canister. About 6 months ago I changed the plug wires to some Accel wires I had here and got a new cap and rotor with brass inserts. Forgot, I changed the thermostat to a fail open 195 about 4 months ago. Changed one of the rad fan motors that was going bad and changed the rad cap (I am suspecting after yesterday that the rad cap is not holding pressure as I could hear bubbling in overflow when I took temp sender out).

I estimate about 12-15k miles on engine. it does "miss" a little at idle which I always attributed to cam (but maybe not as its not a big cam). But the cam has been in there for the last three inspections and passed.

I was concerned about the closed loop and engine temp not reading correctly so I just bought the temp sender in the head, O2 sensor, and the egr. When it comes in tomorrow I will crank it and see if it runs better and goes into closed loop.

And to top it ALL off, House A/C compressor is not coming on so I am working on that too.

 

Temp sender in the cyl head is only for the gauge and will not affect ECM. The ECT sensor in the front of the manifold(yellow wire/ black wire) is the one that the ECM uses. It has a significant affect on fueling and the ECM's ability to maintain closed loop fuel control. From your test results, the engine doesn't seem to have a fueling issue as the CO is pretty close to ideal. Generally, I want to see CO at about 1/2 of the limit(.60%). Yours is off by .50% but that's not terrible. You really need to nail down the cause of the idle misfire. Monitoring BLM and INT, or if your vehicle's software is new enough, Long and Short term fuel trims at all operating ranges can help isolate a fuel control issue to either fuel supply, fuel control, or inlet air leak. You may have a runner gasket leak which affects only one cylinder. Propane or brake cleaner will help you find this. Watch short term fuel trim for a response as you apply the chemical.

Since you passed with this engine configuration before, your cam is obviously not the problem. You know better than anyone if the engine is running differently now than it has in the past. For instance, does it idle rougher? Your problem is at idle and since high HC is caused by misfire, you need to decide if you have a new idle misfire that wasn't there the last time you tested the vehicle. If you think the engine runs just fine, retard the timing 2-4 degrees for the test and replace the catalytic converter. Each 2 degrees retarded will reduce HC by 300-400ppm on a fully warm engine, and a new cat will reduce HC by 400ppm. These are rough estimates based on my experience but they are good basic guidelines. Remember, the key affect of reducing timing is heating up the exhaust manifolds. Hot exhaust manifolds significantly reduce HC emissions.

One more question, is you AIR system working? Was it working the last time you passed the test? Air injection reaction, as the acronym spells out, is intended scpecifically to reduce HC emissions by helping to heat up the manifolds by injecting oxygen rich fresh air into the exhaust stream which in turn causes re-combustion of any HCs in the exhaust. The added air also helps speed up heating of the catalyst. Once the initial after start enrichment is done, (about 60 seconds after cold start) the AIR switches to the catalyst where it helps oxidize any remaining CO or HC.

 

Thanks for the info. I will retard the timing some. Trying to avoid buying a cat but will if needed. I have driven it two days now to work (32 miles total) and it is idling better. I did put in some injector cleaner, that may have had an effect or it could be the ECM adjusting. Power seems to have picked up too. I don't run the car hard, just drive it to have a fun work car.

I found another vac leak that was not so small. Put a clamp on.

If the thought had even crossed my mind that the AIR system wasn't working I would have replaced it or at least started testing it. But I don't really know. The AIR pump is new with about 10,000 or so miles. No check engine lights. I will do a search for ways of testing the AIR. AFAIK, it was working last time and the AIR pump was newer then too. I put about 4500 miles per year on the car. I had no reason to suspect it, until now.

I keep this engine close to factory and well maintained. But I'd rather have a solid roller, closed chamber heads, victor jr, 850 df, dp, mech secondary, MSD, etc and more etc. I'll be 50 tomorrow, its nice to dream about the good ole days of no emissions...

 

We can actually make big power while maintaining emissions compliance. It just costs more. It is easier when we don't have to worry about DEQ. My IROC is very fast, and it doesn't have to pass an emissions test. The fuel injected beasts of today also run alot better than those old carbureted rods used to.

A quick test of the AIR system is fairly simple. On a cold start, there should be forced air at both check valves above the exhaust manifolds. You can loosen the clamps and remove the hoses momentarily to check. Remember, you only get a few minutes or less after cold start to check for air there. After that, there should be constant forced air at the check valve leading to the cat. This check valve is at the rear passenger side corner of the engine bay(as I remember). If the system does not seem to be operating as described, look for forced air at the diverter valve(the big black plastic piece over the RH valve cover). There are two switching solenoids that control air flow to either the manifolds, the cat, or out to the atmosphere. Air should only be diverted to atmosphere at high engine speeds, under decel, or if there is an engine control fault.

BTW, I'm 55 and I still love horsepower and speed.