Failed Low Idle TX SMOG Horribly!

jfn · Oct 20, 2014

Hello all. My '93 2.3L 5spd, which I have owned since '95 w/ 15K miles & and now sits at 214K, failed low idle emissions w/ 2x Hydro Carbons this past weekend. Below are my numbers for both high and low idle test scores.

High Idle

HC (ppm) 220/89
CO (%) 1.20/0.40
CO2(%) /13.8
O2 (%) /0.9
Dilution >6.0/14.2

Low Idle -- Where I failed
HC (ppm) 220/556
CO (%) 1.20/0.78
CO2(%) /12.0
O2 (%) /3.1
Dilution >6.0/12.82

Maintenance up to this point include
-tune up/fuel filter replace 1yr ago
-cat was replaced 8 yrs ago (aftermarket bolt on for ~$100)
-Oil change less than 500miles

Any ideas would be appreciated. Dont want to continue to have to drive to SATX (located in ATX) to get an inspection sticker. Note, the truck is registered in a non-emissions county, hence the reason why I can get a way with going to non-emissions county like Bexar.

-jfn

RonD · Oct 20, 2014

Contrary reasoning high HC levels at idle can be a vacuum leak, it causes a Lean mis-fire sending unburned fuel out the exhaust.

Does the engine miss a little at idle?

Could be vacuum hose but more likely an intake gasket that just effects one or two cylinders.

Another possibility is the thermostat, 2.3l runs cold if t-stat sticks open, computer runs fuel mix based on engine temp, colder engine gets more fuel.
Stock t-stat should be 195deg, some in colder climates run 205deg, just to keep 2.3l heater working, lol.
Temp gauge should be above 1/3 and below 1/2 after 5 minute warm up, if it is lower t-stat is bad or the wrong one, i.e. 160 or 180deg

tomw · Oct 22, 2014

You can also get high HC readings if there is an oversupply of fuel. That could be leaking injectors, faulty pressure regulator. One other thing that caused an almost brand new 2.3 to fail was, I think, a coating of stuff on the inside walls of the intake manifold. The EGR flowing in along with the PCV vapors, may possibly lead to a coating that will absorb some fuel which it will give off as the engine runs, similar to heavy carbon on the backside of the intake valve holding unburned fuel for a while.
After spraying carb cleaner (careful of cat safe) all over the inner wall, it passed.

jfn · Nov 12, 2014

The issue was my catalytic converter. The question now I have is why are my catalytic converters going bad.

The last converter I installed was 8 years ago and I have at max put on 60K miles. Something else has to be wrong I am thinking.

Will post my emissions results after new cat is put in.

tomw · Nov 13, 2014

Catalytic converters don't die, they are killed. - Sam Memolo ... auto TV/Radio host & mechanic for 30 years...

If you feed it too much unburned fuel, it will happily burn the fuel and melt itself. If you feed it mis-fired cylinder contents too much, ditto the previous.
If you use RTV silicone, (room temperature vulcanizing) the vapors can coat the catalyst bed.
If you use an un-friendly choke & carb cleaner, it can damage the converter (don't know exact proces...)
If you use un-friendly gasket sealers, same thing.
If you have leaky injectors, bad plug wires, or worn spark plugs, misfire can occur more often.
You might want to read up on converter failure causes.
tom

jfn · Nov 25, 2014

Agree 150% tomw.

The problem is trying to find a shop that can do the proper diagnosis other than going down the list of replacing:

1. Fuel injectors (never changed/cleaned)
2. spark plugs/spark plug wires (changed last year, less than 6k on them)
3. exhaust valve stem seals
4. piston rings going out
5. anything else ?

I would be happy to continue the investigation but when a dumb shop charges you two hours @ $100/hr to do a compression check.

Anyone around Austin, Texas that can help ? I have a bad back and have limited ability to work on my truck.

-jfn

tomw · Nov 26, 2014

You can rent or buy a fuel pressure gauge. Connect to the schrader(sp) valve on the fuel rail. Energize the pump by cycling the ignition from OFF to ON to OFF several times. The pressure should register, and stay up for at least a minute or so after you de-energize the pump. The manual specifies a number of minutes to hold pressure, not remembered by me, but in general if it will hold pressure for a minute, things are pretty good, i.e., check valve is good, and no injector is leaking significantly. It does not take much fuel volume to lower the pressure in a semi-solid volume.
If that is good, I'd check the stat as rond mentioned. A leaky or slow stat can get the temp close, but no cigar, leading to poor mileage and excess HC. In most cases, a failure is caused by misfire. You can get a rich mix because of fuel leaks, misfire, and bad O2 sensors. Leaks speak for its self, misfire can leave excess O2's in the exhaust, and the computer will try to add fuel as that is 'lean', a bad O2 reads low voltage, which is a synonym for LEAN, so it will add more fuel.
tom

Failed Low Idle TX SMOG Horribly!

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