I re-failed my emissions test -Need help determining cause

[mariner33]

Hi Everybody,
I just re-failed my emissions test, unfortunately. It passed the idle and cruising speed Hydrocarbons test (HC), as well as the idle Carbon Monoxide test (CO), but I was way over the limit on the cruising Carbon Monoxide percentage.
The technician gave me a hand out that briefly (very briefly) explained the CO test. Evidently, CO is "partially burned fuel". Does anybody know what would cause my high levels? and or how to fix it on my own? Here's what I did so far;

-The vehicle had high miles (over 200K), and the initial CO reading was 4.5 % when I first took it in for testing. The limit is 1.0%, so the vehicle definitely failed.

-The engine had a bad rod knock, and since it had high mileage, I assumed the engine was well worn, although, it still had decent power.

- Rather than remove and rebuild the entire engine, which would cost way too much, I rebuilt the bottom end of the engine (new crankshaft, main and rod bearings, oil pump, timing chain and gears.

-I then re-timed it, after replacing the plugs, wires, cap, rotor, and air filter. The engine runs very smoothly and quietly now, with no excessive oil consumption and decent power. I was hoping that the worn timing chain and gears were throwing off the timing during the cruising portion of the emissions test. However, as I mentioned, it failed the re-test.

-The good news is that the CO % is down to 2.5 % now, but it needs to be below 1.0% to pass the test.

Here’s a picture of the results sheet;

http://mediaservice.photoisland.com/auction/Nov/20041132335210053274955.jpg

Can anyone who knows more about automotive emissions direct me to a site where I can learn more about them and how to repair them? I don't want to take the vehicle to an authorized emissions specialist, because I like to fix things myself to save money. Plus, I want to learn more about emissions.
I've heard about products you can add to your gas that will help lower emissions for testing purposes. Does anyone know more about them, like what they are and how they work? Thanks for any help anyone can offer. The vehicle is a second car, so it's not critical that I pass emissions right away, but it would be nice.

 

[mariner33]

I forgot to mention, it's a 1986 Cherokee Laredo with the 2.8L Chevy 6 cyl engine, Automatic. Also, I don't think the previous link came through. Here's the end of it. Just add the "http://" before it.

mediaservice.photoisland.com/auction/Nov/20041132335210053274955.jpg

 

[Bounty__Hunter]

Here's some tips I picked up from another site:

I've had cars of questionable emissions in the past and it seems that a higher octane fuel and making sure it's good and hot just before testing has helped me. I've also fine-tuned the carb on one of the older emissions test machines till it met the parts per billion requirements.

4 bottles of Heat in my tank and I passed. Run the crap out of it & get it nice and hot before you go as well. I had mine hammered waiting in line & they where like WTF!!!

So I went home and advanced the timing just a bit, hoping it would help burn up a little more of the fuel (with the Nova distributor, timing is a bit of a shot in the dark, anyway), leaned out the Weber's idle circut just a bit and took it back in... I am not making this up when I say I blew about 1% of the allowable in every category and passed in under 30 seconds...

 

[mariner33]

Thanks for the tips. I've heard about the bottles of "Heat" trick. I think the primary ingredient is isopropyl alcohol, but how would that reduce emissions? Less carbon atoms in the isopropyl molecule than there are in the regular gasoline molecule I suppose. I went to the auto parts store today and found a bottle of something called, "Guaranteed to Pass Emissions" that you're supposed to add to a full tank of gas. It's supposed to clean the carbon build-up in my intake and exhaust systems. Does anybody know what the ingredients are in those types of fuel additives amd do they work?

 

[berettajeep]

TJ disconnects

200k ? Is the Catalytic Converter original?

 

[mariner33]

I'm not sure. I bought the Jeep used, but if I had to guess, I'd say it probably is the original. I'd rather not replace it because those babies are expensive. I only need to reduce the CO emissions by 1.5 more percentage points to pass the test, so I'm seriously contemplating the "heat" trick or some other emissions lowering fuel additive. I just would like to research it more. Can these additives hurt my engine?

 

[MudderChuck]

The alcohol, slows down the burn a little (actually lowers combustion temp.s), to help with complete combustion. The EGR valve does the same thing. But actually the hotter the cat gets, the better it works as long as it has sufficient oxygen for the catalyst.
But I think a higher heat, may be better solution.
My motor is different than yours, but unhooking and pluging the vacuum line to my EGR, drove my CO, down to almost nothing (more heat at combustion). I´d say two posibilties are a tired cat. and possibly a faulty EGR. Faulty EGR usually makes for a really bad idle.

 

[TwistedCU]

At you're local uato parts store should be a bottle of stuff that guarantees you passing. I wish I could remember the name. Works like a champ. They won't hurt your engine unless you put more than recommended in or did it all the time.

 

[jacobdown]

Ive had the same problem, and i found a cheep easy fix. Go to your local hardware store, and get a bottle or can of denatured alchol. Get the smaller of the cans. Wait till your jeep is on a 1/4 tank and add the whole can. Drive around and get the motor hot, then go get the test. This wont harm your engine. Ive done it twice and it worked on my neighbors Bronco. You can find this stuff in the paint section and costs about $10. It worked for me hopfully it works for u if u tyr it[/b]

 

[jay79cj7]

Speaking from theory rather than experience: CO should be formed in higher levels when there is not enough oxygen for the fuel to burn cleanly (CO2). It means the fuel is burning, but it forms CO instead of CO2. Could you be running rich? A catalytic converter is a catalyst to convert unburned fuel (hydrocarbons, HC). I do not believe that the cat itself would contribute to the level of CO, because that is a byproduct of combustion, not a leftover.

 

[mariner33]

That makes sense to me. Although, I think the cat also converts some CO to CO2. If the carb was out of adjustment, I'd expect to see a failure during the idle part of the test as well. It might be a little on the rich side, but the engine is running smoothly and the exhaust is clear and smells normal. Anyway, I only have to lower the CO amount by 2 %, so I'm going to try the fuel additive method first. I bought a bottle of something called "Guaranteed To Pass" at the auto parts store. It only costs $7, so it's a inexpensive approach. I'm guessing there's a lot of carbon build-up in my engine, and this stuff is supposed to clean it up. In theory, the carbon build-up reduces air flow and creates tiny pockets where fuel can hide with out being burned or only get partially burned. Who knows? I kind of want to see if this stuff really works or not, so I'm going to give it a try. The directions say I need to add it to a full tank of gas and run it until near empty before driving to the emissions test center, so it may be a while before I find out the results. I'll post again after I take it in so you guys will know whether or not the stuff really works. Thanks for the help.