Emissions testing woes

[rich_e777]

For the third time my car has failed the Hydrocarbon number for the emissions testing here in Tenn. last test after redoing head, LIM, UIM, injector O-rings and all the other misc. parts and gaskets I mentioned in the "what have you done to your car" thread it had a HC number of 269, 220 is what is required to pass. At that time I still had about a half tank of fuel mixed with stuff to clean the carbon build ups out of the engine, well I did it better with a pneumatic wire brush and attachments. Today all I did was change the spark plugs and got a reading or 609!!!!!!!!!!!!!!(on 87 Octane) WTF? The engine is as smooth as ever and no problems other than a weird oil pressure issue which im sure now is associated with the wiring not oil pressure itself. The only thing I can think of at this point is a bad CAT. converter which is about 4 or 5 years old or one of my injectors is acting up. Is there a way to test the injectors in my car or one from a junkyard? I have a multi-meter but an elementary understanding of what the settings need to be at to read it.

 

Now there is a hiss coming from just behind the PS pump, which I thought was a vacuum leak in the UIM but when I sprayed some carb cleaner around that area the engine didn't seem to respond, and it is my understanding that if a leak where present there that it would kill the engine. Also the hiss seems to come from within the plenum more towards the center. I'm up for an ideas to pass this shit legal or not, I've about had it with this gubmint and its regulations. 5 more years and I can kick the cat conv goodbye and get antique plates.

[RobertISaar]

to really test the injectors, you would have to pull all of them and hook them up to a flowbench and watch for spray pattern, volume, etc.

 

HC = unburned fuel, so you're either running rich over all of the cylinders, a misfire, cat...

 

could also have one cylinder running leaner than the others. when that happens, the PCM richens up all of the cylinders to try and get the O2 sensor readings back to where they should be. if this were the case, after running long enough the plugs could be pulled and you'll find 5 that show excessive fuel and 1 that looks fairly normal. when this happens, the cat doesn't really function due to a complete lack of free oxygen. both the CO and HC conversion processes require free oxygen to function. NoX doesn't require an excess of oxygen. one injector flowing less fuel than the rest can cause the same effect.

 

 

 

since you have a smooth idle, you probably aren't experiencing any kind of misfire.

have a way of checking fuel trims? that will give some idea if the O2 sensor is causing the PCM to command any richer than base calibration or not. if it is, that could be a sign for either a failing O2 sensor or injectors that aren't quite flowing the way they should. wouldn't necessarily be able to pick out if a single cylinder is having a problem though.

 

otherwise, that hiss bothers me and would possibly explain everything. also, it seems a lot of carb cleaner these days isn't as flammable as it used to be. i've been hearing recommendations of starting fluid instead, that stuff will certainly burn(for better or worse).

 

 

IF there isn't one(or more) cylinders causing the average of the cylinders to run rich, then i would look at the cat.

[skitchin]

FWIW I would verify the IAT readings as well. Low compression on one or more cylinders is also possible. Beyond that I think saar pretty much nailed all the scenarios.

[RobertISaar]

low compression would likely show up/feel as a misfire. of course, different levels of "low" can complicate things.if it were rings, i would expect a lot of fuel in the oil as well. valves.... raw fuel right out the exhaust valve could cause interesting stuff.IAT isn't a HUGE contributor to much in the calibration, but always worth investigating. CTS can be the difference between undrivable turd and factory-smooth. that would potentially dump huge amounts of fuel into the engine, along with the possibility of an excessively high idle speed.

[rich_e777]

I think I have access to a compression gauge but not sure about how to go about testing the fuel trim, searches are pointing to scan tools and I don't know of one for the obd 1.5. I think that's what mine is, Also the O2 sensor is about 5 or 6 months old. On my gasket job I did find some injector wires that had the coating chewed up on it somehow and I taped those two up with electrical tape. Could that have something to do with it? Also how long should I drive it so I can see any evidence on the plugs, put about 50mi on it today after the change.

[RobertISaar]

good scanners and aldl cables will work to read out the datastream from the PCM.

 

what brand of O2? please don't say Bosch, otherwise expect to replace it. those just don't play well with GM units at all. Denso/Delphi/Delco seems to be where people have the best results.

 

as long as the wires were isolated from each other, should be fine. if i had a section of wire that was bare of insulation or even the copper being compromised, i would have chopped it out and soldered in a replacement section. the injectors only draw around 1 amp each, but with something that critical, i'd rather go overkill than risk redoing it.

 

how long before you would see that kind of issue on the plugs, i really don't know. could be now, could be another 50 miles, could take a couple thousand. depends on how far off the one cylinder might be.

[crunkGP96]

I'id say with how high your #'s are reading, it might be the catalytic converter. They do go out, even with lower miles. I had a few issues with my car when i first got it, replaced some parts and finally figured out it was a plugged cat. My car only had 93k on it. Just letting you know that they do go out on these cars. I replaced it for about $160 and the car has driven like a dream.

[rich_e777]

I believe it was a Bosch. Sat around for awhile before I put it on but it made a big difference when it did. Should have stayed with AC Delco, never done me wrong before. My converter is old and I do question the integrity of the shop that put it on, but they did have flanges on both sides to make a fast swap possible, however Midas screwed that up so I will have to pay a shop to do the job, again.

[Imp558]

I like Robert's suggestion about the CTS, and the IAT can mess with you too, if one of them are reading too cool the engine can run pig rich, which would not only fowl your numbers but screw you at the gas pump. How's your fuel economy? Do you have the ability to scan the car and see what the PCM thinks the coolant temp and intake air temp is? Bearing in mind that the coolant gauge reads a different sensor and can't tell you what the pcm sees.

[Pontiac6KSTEAWD]

The hiss, to me, sounds like the vacuum spider under the upper intake plenum. Luckily, your EGR is digital, so you wouldn't have to worry about that. However, it would mess with your fuel pressure regulator, you emissions charcoal recovery system, probably your PCV valve, and possibly your HVAC ducts in your dash.

 

All of those, except the HVAC, will mess with your emissions. I will also agree with the CAT, but would recommend starting with the Vacuum spider. It will be far cheaper to fix, and correct other issues in the process. Such as... (read on)

 

While you have your intake plenum off, you can OHM check the injectors. I can tell you how to OHM check the 2.8/3.1 cars, but not the 3x00 cars. Hopefully someone else will have the numbers you are looking for there.

[RobertISaar]

the 3100 injectors will be in the 12-16 ohm range if they're not shorted internally. basically the same resistance specs as the 3.1 injectors.

[Pontiac6KSTEAWD]

So basicly, 11.7 and below is bad, 11.8 is borderline, and 11.9 and above is good. You do want them to all be reading within 1.2OHM of each other thou.

Edited October 30, 2013 by pontiac6ksteawd

[RobertISaar]

GM's official spec on them is 11.8-12.6. not sure why i thought "up to" 16...

[gp1991]

i cant believe you have to do emissions on a 94 in the first place thats just not fair. I would fail for the next few cars behind me if they made me test lol

Edited October 30, 2013 by gp1991

[l67ss]

Just tag it in arkansas, youre close enough

[ManicMechanic]

Last year for my '89 to go through emissions and he made it pass. Gotta love a guy like that.

[Schurkey]

A rich mixture will drive the CO sky-high before affecting the HC much. If the CO isn't high, you're not rich.

 

High HC is typically misfire, including a mixture so lean it won't burn. ANYTHING that causes misfire causes high HC, except for (total) lack of fuel. I suppose a defective cat could increase HC, but I'd be more concerned about high HC ruining the cat. In other words, you could replace the cat, but if you don't correct the high HC, you'll replace it again...and again...

[rich_e777]

Alright will be pulling of the plenum and testing the injectors a little later I can test resistance(Ohms), might as well pull the IAC sensor of the TB and the EGR clean it up to couldn't hurt. This "vacuum spider" that's the first time I`ve heard that term and have no clue what that is. I wish I could remember what the CO and CO2 numbers were before my last test, but the CO now is 1.06 and the state limit is 1.2, and the CO2 is 12.7 but TN doesn't care about such things. Also could it be that I have to put it through some drive cycle after having the battery, plugs and a few sensors disconnected? If I have to get another converter Its only going to be on the car to pass the test and its coming right back off. Road trip to AK sounds good but with my suspension in its current shape I don't want to push it. It would be about a 10 hour round trip on expired tags, no insurance, and I don't think I have enough ammo to fight my way through Memphis twice, once maybe.

[rich_e777]

Last year for my '89 to go through emissions and he made it pass. Gotta love a guy like that.

Yesterday I had a guy who could barely speak English and spoke no Spanish. I had to tell him how to do the test as he wouldn't let me rev the engine at all. Every other time Ive done this test I held 3000rpms for a minute or so. Then his manager came over and started talking to me like I didn't know anything about cars. He apparently didn't either and could only repeat information he heard from other people without understanding anything.

[rich_e777]

A rich mixture will drive the CO sky-high before affecting the HC much. If the CO isn't high, you're not rich.

 

High HC is typically misfire, including a mixture so lean it won't burn. ANYTHING that causes misfire causes high HC, except for (total) lack of fuel. I suppose a defective cat could increase HC, but I'd be more concerned about high HC ruining the cat. In other words, you could replace the cat, but if you don't correct the high HC, you'll replace it again...and again...

Before I thought the Cat converter I thought that maybe one of my injectors at idle wasn't atomizing fuel and just dripping it into the cylinders. That's what my guts telling me but the Cat is probably over due for a replacement. Funny thing my car is the only one in my known family that has ever had a converter go out(if this is the case) in the last 7 years and some have had their cars longer than me.

[rich_e777]

i cant believe you have to do emissions on a 94 in the first place thats just not fair. I would fail for the next few cars behind me if they made me test lol

5 more years. 25 and older in TN are eligible for Antique plates and in turn are exempted from emission testing and requirements. I hope she makes that milestone and the engine can last me until then.

[Schurkey]

Also could it be that I have to put it through some drive cycle after having the battery, plugs and a few sensors disconnected?

Disconnect the battery, all the adapted computer memory for fuel curve, etc. is gone. Engines often run shitty when battery is disconnected, until they re-learn the adaptive info.

 

If I have to get another converter Its only going to be on the car to pass the test and its coming right back off.

Why? It's not like it's hurting performance.

[rich_e777]

Disconnect the battery, all the adapted computer memory for fuel curve, etc. is gone. Engines often run shitty when battery is disconnected, until they re-learn the adaptive info.

 

 

Why? It's not like it's hurting performance.

I Did drive around a bit after everything was reconnected before I had this last test done. Took it on some back roads for interstate speeds to get the engine warmed up. So I should drive it some more? No problems with that. As for the converter I`m only going to bolt it up to pass the few remaining tests over the next few years and I don't want to wear it out unnecessarily. If that turns out to be what the current issue is, if its not it will stay were it is until the time comes I can legally remove it so I wont have to worry about it getting clogged up.

[rich_e777]

Just confirmed the cat converter is shot, rattling pretty bad. So that's one thing, but I thought one should be able to get a lot of miles out of them, only put a few thousand on it as it hasn't always been my DD. Also curious as to any conditions that would make them where out faster. About to pull the plenum off and find this "vacuum spider". Is that a reference to the way the top of the LIM looks? I do not have any vacuum lines under there just the fuel rail and related wires.

[Pontiac6KSTEAWD]

I call it a vacuum spider, I am sure that's not its official name. But its the hard plastic vacuum lines that are under the intake plenum. They commonly break anytime you are doing any repairs around the throttle body, or under the plenum. Sometimes you can get lucky and just use rubber vacuum hose to repair it.

 

While you are under there, check the PCV Valve, and hose. The hose is a known problem to break when you do any repair under the plenum. It can also be a royal pain in the ass to get back together correctly.