Pull your Catalytic, put a flash light up to one end to illuminate to check for severe clogs. Wash in soap and water. Allow to dry. For stubborn clogs, use a wire to clean out the bee hive.

The cats job is to cook gases. Test the converter with an infrared thermometer:
https://www.youtube.com/watch?v=9VZ5K8n5jj0

Scotty Kilmer recommends a pressure test: https://www.youtube.com/watch?v=IzyvL5tQLzU

But I don't see why you would pressure test the converter, after you have unclogged it. Perhaps, it would indicate a crack where gas is escaping, resulting in a loss of pressure.

Already checked the cat. 200?F inlet, 350?F on the outlet.

Thanks, though. Hadn't thought about washing it!

You don't really pressure test the cat. You test if the cat is causing backpressure by reading the pressure upstream of the cat. I bought an Astro van a couple of years ago, and it had a clogged cat, found with such a test. We drilled a 1/16" hole in the downpipe and applied a manometer, and it read high. The cat was a blue blob instead of a honeycomb over about 20% of the surface. The truck went from a choking, limping, stuttering dog into a warhorse, in fact, it was a semi competent wheeler, pulled a very heavy Cobalt boat from Alcoa, TN to Gaineville, GA over the very steep Blue Ridge at Fort Mountain gap.

Is 350? hot enough i.e. within spec?

You already have the usual suspect in mind- the thermostat. "1/8" above the cold mark" is too cool. If a car runs too cool it tends to throw the sensors off and run rich. My 1989 3.0L had that problem, running too cool (wrong aftermarket thermostat) and crud accumulating in the combustion chamber.

The no. 1 suspect is your state government. Does AZ have smog referee's like California? If so, drive over to the referee and have HIM/HER tell you what is wrong with your vehicle so YOU can COMPLY. Damn, AZ should at the very least do that. Or cross the border into Cali, have a smog test flunk and then go to a Cali referee tell you what's up under California's exacting standard.

No. 2 suspect is a cracked vacuum hose. No. 3 suspect is the control of vapors: fuel filters, evap canisters, etc.

You are going through the problem sequentially, which is good.

I definitely think the temps are suspect. Of course, give it a month and I'm sure I'll be fine. Already well into the 90s here during the day. Won't be long, I'll have the AC fixed and really put the wood to the engine. Bet that raises the temps!

Noticed there appear to be 3 temp sensors on the tstat housing.
- larger, 2-pin, which I assume is used by the FCU
- smaller, 1-pin, above right, which I assume is the gauge
- another smaller 1-pin below the thermo valve on the right

Always a mystery.

Larger two pin with connectors in a tee, pointing forward, is the ecu ect sensor.

Smallest one pin is a thermoswitch to control o/d shifting.

Medium one pin is gauge sensor.

Thermo switch should show either open or almost zero resistance to ground. Gauge sensor should show some temp dependent level of resistance, never open, never almost zero.

That's interesting. My truck is a 5-speed. I can see someone, somewhere along the line, installing the automatic's tstat housing/manifold, but then why do I have all three connected? <img src="/forums/images/graemlins/pfft.gif" alt="" />

Thanks again, Eddy.

I was incomplete. Also controls a/c compressor clutch, killing a/c when overheated, as well as a/t o/d killed at the same time...

P-P-P-P-PASSED!
Timing is everything. (And a quart of 91% rubbing alcohol just in case.)

2.6L emissions failure lessons learned from hindsight:

In order, from made the MOST improvement to LEAST improvement of all the things I did to pass smog:

1. Timing. Target is 7?BTDC, +/- 2?. Even if you think it's set, check it again. Mine was set, but somehow ended up at 10?BTDC. Bumping it up to 6?BTDC (vac advance disconnected, by the way), resulted in a noticeable driveability improvement (and I went from 15 to 18mpg around town). I had been hoping for a 15% improvement over the previous test just to scrape by. Correct timing (and the bottle of alcohol) got me DEEP into compliance levels.

2. General tune up. Air filter, oil/filter, spark plugs, PCV, make sure the thermostat opens. This is a good time to clean up your vac lines, too. Trim off loose ends for better seals, dab a little RTV on any caps, maybe try to follow that vac diagram under the hood.

3. O2 sensor.


Hope this helps someone else. Renewal cost me $101, including $32 in late penalties.
<img src="/forums/images/graemlins/butwiggle.gif" alt="" />

Congrats... Old vehicles can be a bit of work to get them through, but once you figure it out, the right tricks for your truck, then it's not too bad.
-Jon