Failed emissions....

[atarasi]

So I while I was installing the low mileage engine, I thought it would be a benefit, (how? not sure) to chip out all the stuff inside the catastophic convertor. Anyway, so it failed the hydrocarbons limit at idle. I installed the other convertor thinking that that would help. Nope. The carbons are even higher than with the hollowed up convertor. How is this possible?
I will say that when I changed convertors, that also changed the OXS sensor as well. The van idles identical with each. It just smells like it's running too rich. Could this be the throttle body enrichment switch? What would make it run too rich?

[shenan-agon]

[bunker108]

My van has passed every year I have owned with a hollowed out cat.

I was looking forward to gutting it when I pulled the motor to do the heads and a clutch only to discover it was already gutted.

This year it barely passed HC at idle though...I think it was at 118 with 120 being the limit. Passed easily at speed.

[atarasi]

But with an ineffective OXS sensor, wouldn't the idle hunt more?

[tencentlife]

Most any O2 sensor-equipped injection will pass emissions everywhere but CA, and even there sometimes, without the catalyst. The sensor is able to keep Unburned HC in a very narrow range, which is what it controls. If HC goes outside this range for long it will start to burn out the catalyst, which is why there's an O2 sensor in the first place. That's the only reason it's there, but the system is set up around it, so without the sensor things get pretty weird, as in very rich.

atarasi, in your case, since both sensors give similar results, I would check out the signal cable. I was just relating this same thing on another post this AM. That green wire is actually a shielded coax cable. If you slide the rubber cover back up the green cable to expose the end, you might find like I did that the shielding wires are exposed and are shorting against the female sensor connector. If there are frayed braid wires exposed there trim them back a bit, and SOLDER on a new female spade connector to the center wire. At least this way you can be sure the <1v signal is getting to the ECU.

[atarasi]

Thanks Tencent, your explaination makes a lot of sense. Come to think of it, the female part of the plug is a little melted. I'll check into it.

[tencentlife]

Give us a report, I'd like to know how often this happens.

Thanx

[Terry Kay]

If the Van smells rich--it is--

And it may not be the oxy sensor at all.

Take a look at the throttle postioning switch adjustment first.
It the ECU has no idea where the TPS is it'll run very rich, all the time.

It's a wear item, and either needs adjustment or replacing.

Both of my Vans have gutted converter's, and pass emissions testing with flying color's.

The TPS'es are set up right on the money.
_________________
T.K.

[tencentlife]

So, Terry, are you saying that if the TPS is misadjusted, but still at midthrottle is open circuit, that the ECU will ignore all other data and inject too much fuel because of it?

My Digifant IDLES better when the switch is set right, but it DRIVES just as well whether it's set right or not.

And the full throttle closure has never had any discernible effect on power.

[Terry Kay]

<< are you saying that if the TPS is misadjusted, but still at midthrottle is open circuit, that the ECU will ignore all other data and inject too much fuel because of it? >>

It could very well be---
The TPS provides closed throttle and full throttle signals to the ECU for idle stabilization, deceleration fuel shut off, and full load enrichment.

If the TPS isn't adjusted properly or opening and closig at the wrong times it could effect the idle, over fueling in deceleration, or you may not be getting enough fuel at WOT.

The signal's have to be fed to the ECU at a precise throttle postion.


<<My Digifant IDLES better when the switch is set right, but it DRIVES just as well whether it's set right or not.>>

Something else isn't functioning right.


<<And the full throttle closure has never had any discernible effect on power.>>

How can it be possible for the throttle plate to be closed at WOT?

Just curious.
_________________
T.K.

[tencentlife]

Closure refers to the condition of the switch.

<<The signal's have to be fed to the ECU at a precise throttle postion.
>>

Quite true, although it's only one signal, and it only affects the program at idle, by proximity off-idle, closed-throttle deceleration, and I have no doubt there is full-throttle enrichment occurring, but I've never been able to discern any effect. It's a Vanagon, after all. I was being a little snarky, there. None of these programs, however, is in effect at mid-throttle positions, so why would the idle switch being a bit off, as it can only be a bit off, make it "very rich, all the time", as you said? That's the part I don't get.

<<Something else isn't functioning right. >>

Why? Because it has good power in the main powerband?


By the way, do you know of any bigger throttle bodies that could be adapted to the Vanagon? The opening on the plenum would have to be widened, since it's only 1mm bigger than the OEM throttle body, 50mm.

[Terry Kay]

Didifant uses a single throttle switch to signal the ECU when the throttle plate is either in the fully closed or fullyopen postion.
The signal enables the ECU to determine thatone of three auxillary functions ( idle stabilization, deceleration fuel shut off, or full load enrichment ) is required and it activates the appropriate circuit.

The TPS is a normally open switch unless actuated.

One eccentric closes the contacts in the fully closed position ( idle stabilization, decel fuel shut off)
the other is in the fully open position which controls the enrichment ( full load signal )

Correct adjustment of the switch is very important and often over looked, and if misadjusted the engine may surge at idle, cut out durring steady driving or light acceleration, and/ or cause the engine to run rich.

Most folks go direct to the oxy sensor first to correct an over rich condition, when the TPS should be the starting point--then go to the oxy sensor.



<<By the way, do you know of any bigger throttle bodies that could be adapted to the Vanagon? The opening on the plenum would have to be widened, since it's only 1mm bigger than the OEM throttle body, 50mm.>>

No, not right off the top of my head.
Here ya go--trying to stuff more peanuts into that squirrel cage-

Take Care,
_________________
T.K.

[tencentlife]

The cage got bigger, so there's more squirrels, and they'd like more peanuts. I'm trying to keep them fed and head off a squirrel strike. I don't want to have to negotiate a new contract with the IBRRR (International Brotherhood of Rapidly Rotating Rodents) again.

[Terry Kay]

<<The cage got bigger, so there's more squirrels, and they'd like more peanuts. I'm trying to keep them fed and head off a squirrel strike. I don't want to have to negotiate a new contract with the IBRRR (International Brotherhood of Rapidly Rotating Rodents) again.>>

Funny Stuff---- ~ : )

Don't get the brotherhood all wound up now--

Take Care,
_________________
T.K.

[tencentlife]

Oh, they're gettin'wound up already just fine on their own. I mean, they are RRR's (that's 4 r's...), and the Brotherhood is proud of what they do ( Look-For, the Union La-bel...). Man, but the peanuts. It's killin' me!