NoTransistors

!- Well, when I replaced the TPS and accelerator pump washer, and reinstalled the carb, I did not realize that I broke a plastic vacuum tee in the emission hoses. Car ran super lean for two days, and cat seemingly cooked because the computer was diverting the air pump to atmosphere, and not to cat [has a cooling effect]. Exhaust now smells nearly un-catelized, but all plugs are clean enough to eat off of.
Replaced temp sensor today, and maybe now computer will know when to pump into cat [the injection tubes to heads are not installed]. Cat is warranted, and I will replace it for free, minus the welding. Am I right about the cat, as the exhaust is smelly but plugs are clean?

2- The car still runs lean. It was lean before I fooled with the carb. Besides the need to get cooler plugs, What is going on?
Idle is sort of rough, but since the rebuild, take-off is without hesitation [accelerator pump was in bad shape].
I cannot find hose leaks, but the computer should try to compensate for very lean, right? Or is this normal with our 'lean-burn' setup?

3- There are two supplied carb mounting gaskets in kit.
one-hole [OEM style]
three-hole [two primary and a common secondary]

Which might be the better choice?

Thank You,

Seth

Apeiron

The computer has no control over the A.I.R. system, it's all controlled by vacuum. I doubt that it's damaged your cat. Colder plugs aren't going to do anything to make your carb run richer either. How did you tune the idle mixture?

NoTransistors

I beg to differ.
The computer decides whether to divert the pump to the heads or to the cat. There are two electrical connections and two vacuum connections.
The vacuum connections exist to prevent backfire, by shutting-closed the two diverter valves, during low-vacuum conditions.

Clean plugs plus that old-tyme exhaust smell means bad cat.
No other explanation, right?
Something killed the cat, and it was not the dog/cat flu that has been killing pets in the States, in these last few weeks.

The idle-mixture has never been touched.
How lean is this puppy supposed to idle?
During all throttle conditions, there is no hesitation or pinging, on 89 octane fuel. Car has NO KNOCK SENSOR, NEVER HAD ONE.
Too lean, or simply set to meet Federal regulations?
Used to idle somewhat smoother, but never like a pre-smog big-block.

Thank You,

Seth

Apeiron

Ok, the wiring diagram shows that it is actually computer controlled, so nevermind what I said.

Rich smelling exhaust doesn't automatically mean the cat is bad. If it's misfiring, you canl have unburned fuel in the exhaust without fouling the plugs.

NoTransistors

What I smell is exhaust, not raw fuel. If there was raw fuel in the exhaust, it would ignite in a functioning cat, and explode. I am using logic, and not experience.

Seth

Damon

1. If you burnt the cat you'd have a massive exhaust restriction. The ceramic honeycomb that comprises the "bricks" of the cat through which exhaust passes melt into one solid turd inside the cat shell if you really cook it bad. I've had them run so hot the cat was glowing cherry red and I still did no damage to it. They're tough little buggers.

If you have a melted cat you will be down on power in the upper RPMs and hear and loud "hiss" at WOT through the upper RPMs. Like someone letting the air out of your tires when you lay into it. Unmistakable sound once you've heard it the first time.

2. Lean is a relative term. Is the O2 sensor new? What's it reading (through a scan tool)? What kind of duty cycles is your misture control solenoid running at? Can you even hear it ticking away at idle after the motor reaches operating temp? Are you getting any codes from the computer that specifically state "O2 sensor reading lean"? The 14.5:1 A/F ratio the computer tries to achieve would be perceived by most "old school" hot rodders like myself as "wicked lean" using the old calibrated nose and plug readings. But that's what they're designed to run at. Gotta become one with computer controls if you want to stand a chance at knowing what's REALLY going on inside a computer controlled motor- even an old computer controlled carb.

3. Use the one-hole gasket.

NoTransistors

The exhaust does stink.
I barely smell it at idle, but do smell it after stopping for a light.
I did the 6-cylinder dwell-meter thing on the mixture solenoid, and it was exactly perfect.
The computer throws no codes, so I suppose I am not used to EPA-strength lean.
Used to tune my Chrysler 440 by smell, and it was able to run very lean and very smooth.
Same with my Triumph TR-7 four-banger.
I have a new Bosch Oxygen sensor.
Don't know if mixture solenoid still runs at hot idle, but I can disconnect it to see how things change. Hot idle used to change dramatically when I pulled connection while running.

Does a cat need to melt, to be relieved of the material that makes it work? Can it fail to clean the exhaust without becomming a puddle of s**t first?

As I said, the plugs are spotless if pulled right after a run.

Seth

NoTransistors

I have the warranty-exchange cat, and it should go in Wed or Thurs, at the local muffler shop. The only reason I am doing this, is because I have no definitive answers as to whether or not a cat can get spoiled without a melt-down.

If the plugs were dirty, it would mean that a rich condition exists, and there is too much crap for the cat to clean up.

If it were very rich, then some un-burned fuel would be igniting in the cat.

But as I have said, the plugs are so clean, that you know the engine must be running clean and lean. The smell is not richness, but just un-cleaned exhaust.

Hope I am not wasting my energy on this notion.

I think that this existing cat is failing, and while it can handle the flow of an idling engine, a drive down the street is just too much for it to deal with.

Seth

NoTransistors

.