Smog-test as diagnostic: Should I have reset the ECM before the test?

[BonzaiDuck]

Maybe this will seem trivial to other enthusiasts here. You've seen all my wild threads on my 95 Trooper's new audio system and other aspects of its resurrection.

I found my "Solid Gold Repair Shop" for the present and future maintenance of this SUV, and I occasionally give the staff some lunch money or a couple bottles of Martinelli's Sparkling Cider when I drop by the shop. Why? Because I'm obsessive enough about my Trooper-as-ongoing-project that I engage my service-advisor in more e-mail messages than he deserves. Which explains my misgivings about pestering him today during this joyous holiday season.

I was anticipating my 2022 California smog-test, because I watch the numbers. I've kept the records of bi-annual tests going back to 2002. For this year, I anticipated some improvement in the numbers.

As I mentioned elsewhere in a thread about "warming up your vehicle in the morning", I've used Marvel Mystery Oil (MMO) to slowly clean the engine and get rid of noises from sticky valve-lifters. This has all worked out quite well. And -- the engine runs better than I remember. That is, there has been noticeable improvement in engine performance -- runs smoother, quicker response, etc.

As I understand it, and members are encouraged to correct me, the ECM, engine-control-module or "main computer" collects data as the vehicle is being driven, and continuously adjusts the fuel mixture and other factors to assure best gas mileage and performance. To clear my ECM, I must disconnect the battery and twist the ignition key to "on" for 30 seconds. The last time I did this was about 18 months ago.

While the Trooper passed its 2022 smog-test as required for registration renewal, I was not happy with the numbers. HC ppm "MAX" acceptable is 60, and "MEAS" measured ppm is now 60 -- 19 ppm above the 2020 test. CO% is about what it was in 2020. NO ppm is up to 254 from 207. In past years, it had been higher and lower in a random pattern (as I said, I have 18-years-worth of smog-test results.)

So, "PASS" notwithstanding, I may have missed my chance to see if there had been actual improvement. Whether I did or didn't depends on what effect it might have had to reset the ECM before taking the car in for smog-test yesterday.

So. SHOULD I HAVE RESET THE ECM? I will probably reset it tomorrow, when I intend to put the battery on the charger.

Second, I've received some advice to use a product called "Cata-Clean" to rejuvenate the catalytic converter -- hopefully to get better results for HC-ppm and NO-ppm. Customer reviews of the product seem pretty solid at five gold stars. SHOULD I USE THE PRODUCT NOW? OR SHOULD I WAIT UNTIL A FEW MONTHS BEFORE THE NEXT SMOG-TEST?

 

[NutBucket]

The quick answer to your question is it probably doesn't matter since the ECU in your vehicle is fairly simple compared to modern ones. And the issue of HC could be very simple. Cats work better the hotter they get. If it sits too long between you arriving at the shop and the tech doing the measurement it could make a difference...though to be honest if that's the issue the reading will likely be dramatically different (like pass/no pass). So it could just be a simple difference in readings between machines, etc. I wouldn't worry about it at all since you're still firmly in the "pass" zone.

 

[BonzaiDuck]

The quick answer to your question is it probably doesn't matter since the ECU in your vehicle is fairly simple compared to modern ones. And the issue of HC could be very simple. Cats work better the hotter they get. If it sits too long between you arriving at the shop and the tech doing the measurement it could make a difference...though to be honest if that's the issue the reading will likely be dramatically different (like pass/no pass). So it could just be a simple difference in readings between machines, etc. I wouldn't worry about it at all since you're still firmly in the "pass" zone.

Sounds reasonable if I put my brain in common-sense mode and ditch the compulsive-obsessiveness.

The better this old beast gets for my efforts, the more I focus on minor things. I DID go forward to order a 2-pack of the Cata-Clean.

I told my service advisor that I believed there were two types of used-car-owners or two extremes. There are those who need a beater to travel to work so they can get their daily bread. Too many expensive repairs and they may ditch the car and buy another used one. Then, there's the local cement-factory tycoon who appeared in our monthly "Villa" magazine. He has a collection of classics; if he needs to spend a bundle to stave off disaster with his '64 Eldorado, it's chump-change to him.

The average cost with insurance for owning any type of passenger vehicle in Alaska (averaging used and new together) is about $250/month. The average in California is $550/month, and I -- living in CA -- have spent on average over 20 years about $240/month. These last three or four years showed some lumpy payouts -- tires, ball-joints and a harmonic balancer this year -- but they all figure into an average of the last 20 years. So for me, it's a matter of budgeting and anticipation. If I don't have to replace a catalytic converter now, then it can certainly wait. Maybe I won't ever need to do it, but this year's smog-test made me wonder.

As for the temperatures of the car when I took it for smog-test, I made sure to run it up and down the highway for 40 minutes, and then I left the engine running while I waited for the tech to start the smog-test. I have another two years to worry about failing the next test. But I don't think there will be very much to do with the engine or fuel system then if it does fail; my repair shop should be able to fix it. Or -- maybe the cat-converter is going south, but that's still not a huge amount of money if it's the only major repair to do in a year's time. I just wish my numbers had been a tad better.

 

[NutBucket]

To me the numbers are perfectly fine given the age of the vehicle. As you say, nothing to be concerned about until they actually become an issue. Unless there's some major mechanical failure there probably isn't a whole lot you can do to restore them without spending an unreasonable amount of money.
Luckily your truck is old enough you can use aftermarket cats if it needs replacement. On newer cars I believe your only choice is OEM due to the infinite (money grabbing) wisdom of the state.