Intermittent Stall at Red Lights

[metalforever]

The O2 sensor is unplugged. How do I plug it back in? Sorry if this is a basic question.

[Abscate]

[E1]

For what it’s worth…

We relocated camp this week after being mostly parked for six weeks.

Our fuel level was well below half a tank over that period, with the only drives being fives or so miles to town, and same back — about eight round-trips total.

I let the gas run down more than I typically do, and barely made it to town the last time before moving on. It acted like it was running out of gas, as it had when fast-idling when working in the engine bay a few days prior.

But cars don’t run and then drive several miles if running out of gas. I filled the tank and added a load of the red HEET. It ran fine for about thirty miles twice, then acted like it was rich and flooding. We pulled over twice, suspecting possibly the catalytic, and sure enough, the inlet temps were 450 inlet and EIGHT HUNDRED outlet. The 400 was normal, but in general I see 100-150 degrees higher on the outlet when all is good.

After the second stop, I added a bottle of Lucas injector cleaner, and idled a few minutes to get it to the injectors, shut down, and waited a half hour for it to get to work.

We fired it up and drove about 100 more miles to our destination, outlet temp was back to 550ish, and unless the catalytic is failing the issue is likely completely fixed.
_________________
‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[TornadoVan]

Sorry for replying this late.

I stand by my original guess.

When you have a bunch of water in there and mix it with alcohol, then run it through the engine, you end up with a false lean condition. That water is effectively being turned into steam that is then registered as O2 by the O2 sensor. The ECU sees this as a lean condition, and so drives the mixture RICH. Now, you have water AND a rich condition leading to further incomplete combustion. The job of a catalytic convertor is to burn unburned or partially burned fuel up before it leaves the exhaust system, and that is exactly what it was doing, burning up extra fuel (the driven rich state). Do this long enough and you get increased outlet temps on the cat, as the cat is working overtime, just as you saw when you measured it.

Since you added injector cleaner and HEET, you've dealt with, and got rid of, the initial culprit. Don't worry about the cat being damaged as long as it didn't run like that for more than a couple hours, and the internal ceramic core didn't actually melt. You'd know if it did--that cat would have been glowing like a sunset at that point.

I used to add water to the intake of older cars, especially carb engines, to intentionally steam carbon out of the cylinders and to burn off any soot that may have accumulated in the cat. I called it a Hydro-Tune. Basically steam cleaned the combustion chamber and cat in less than 30 seconds. I've made hundreds of cars pass smog tests with this simple procedure.

I think you're golden, dude.

[E1]

Thanks, our issue has resurfaced a couple times but overall *seems* fixed.

We haven’t heard back from the OP — who isn’t me — and hope theirs is fixed, too.
_________________
‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman