Well that sucked.
My car failed the emissions test, it's HC value was 200-300 out of 100 allowed at idle(fine at higher RPM's), lambda value was too high as well.

Now I took it to the mechanic and they pulled out this rubber hose that apparently supplied air to the cats, after a while, a rather long while I thought, they dropped to within levels, they said this was the problem, but it hadn't been a problem before I had new cats put on so whats the problem here really?

The lambda values got to within allowed levels(1.03 is the highest, it was varying around 1.15-1.7 before) too once the engine was going at 3000-4000 RPM's.

I hear this has something todo with the O2 sensor located in the exhaust, could it be shot? And why are the HC values too high unless I remove that hose(whatever it is, guess it's got todo with the AIR system)?

 

Catalytic converters will not cure and excess HC problem. You're either dumping too much fuel or not lighting off the fuel well enough. Fuel pressure that's too high, a faulty 02 sensor, and misadjusted TPS sensor are all common problems, but are not the only problems that contribute. Weak ignitions are the #1 culprit.

 

So it passed after they made an exahust leak? When was the last tune up? Last time O2 was changed? What is the timing set at? Maybe do a search on 'emissions and hydrocarbons' would bring up a few things for you to review and then apply to your situation. Do you have the entire test data to post?

 

So maybe new sparkplugs and wires? This problem has apparently developed over this year and I have not changed the sparkplugs.

As for the lambda they suspected the O2 sensor, is it alot of trouble to replace one of those?

Red Devil, never changed the O2 sensor or given it a tune-up, it passed last year just fine, which was when I bought it so I didn't see the need for it.
I do not have the entire test data no.

 

I went and took this picture of the equipment in question:


Now the one with the green arrows is the one that I can pull out to lower the HC values, the green arrows show that there is air in this going that way, it's very soft, hardly any pressure at all.

Some of what I read on that search makes me wonder if I got a faulty valve in that AIR diverter valve, thats the black box there right?

Apparently one could tell if it was sticking by pulling one of the hoses and see if air was coming out of it, if it was then the diverter valve is stuck and sending oxygen to the manifolds instead of exhaust.

 

None of the hoses on the diverter valve should produce air. The diverter valve forces air into the hoses. So I'd say you have a faulty check valve in the cat line.

Also, check if your diverter valve works the way it is supposed to. On cold startup, the diverter valve should direct all air into the manifolds (the hose with the plastic T in it) and when the engine warms up, the air should be diverted into the cat (the green arrow line, but reversed flow) to provide air to complete combustion of unburned fuel. The check is easy, just unplug the hoses and check the air flow with your hand, it's not hot.

If you find out that your diverter valve is not operating correctly, you will need to troubleshoot it to see what is causing it (valves sticking, burned out, connection, ECM ... probably in this order).

Hope this helps.
Lou

 

OK, but one of those hoses should produce air for the diverter to well... divert, right?

Two hoses ought flow only one way and the third the opposite direction, so which one is the one that should flow differently from the others?

Green, Blue or Red?

EDIT:
Wait I think I got it, it's red right? Blue goes towards the manifolds and the diverter ought to shift the air into it towards the manifolds when it's cold.

So from Red to either Blue or Green.

Also, where else on the cat line as you call it could there be a valve thats faulty?

EDIT #2:
Looks like I got the above totally wrong, there is apparently another hose that supplies the air from the pump.

Seems like the Red hose is connected to the manifold on the other side, I suppose the Red and Blue connections pump air into the manifolds when it's cold as you said then, and then when it's warmer it pumps it into the green hose that goes to the cats.

I'll check tomorrow when the engine is cold and remove the blue marked hose, if I have understood you right then there ought to be coming air from the diverter valve going into the blue marked hose if it's working as it should.


I also have some questions, why does it divert air to the mainfolds when it's cold instead of the cats? I know it diverts air t the cats so they'll burn any left over fuel, this lowers HC values then right, but why divert air to the manifolds when it's cold? Has it go to with temperatures? Must the cats be warm before they can recieve air?

Here is another image as well, is this how it ought to function?

 

AFAIR, the blue hose is for air relief into the atmosphere. See the little "hat" on it?
The pump supplies air into the diverter valves. It's hard to see the pipe that feeds the pressured air into the diverter.

The green hose goes to the cat, the red hose splits into two hoses and goes to both manifolds.

Hope this helps.
Lou

P.S.: I am not exactly sure if I remeber why they run air into the manifolds on cold starts. Something to do with O2 sensors and warming up and rich mixture etc. Don't want to give you the wrong reason. Your manual should explain it. Or do a search here.

 

To heat the cat up quicker.

The TPS won't have anything to do with it.
The '730 will calibrate the TPS's lowest voltage point at power up to 0% tps.

The '730 actually has 3 modes for air injection:

1) Open loop during startup, the air diverts to the manifolds. This aides in the cat and the o2 sensor to heat up faster.
2) During closed loop the air diverts to the cat.
3) On decel, the air diverts to the atmosphere, to avoid backfires.

What you need to do is verify that these modes are infact working. (with a scanner) During open loop, check the air is going to the manifolds, when you enter closed loop, check that the air is going into the cat.

Also, check your idle BLMs, and o2 cross counts. The o2 should be crossing fairly fast. (around a cross per second). Otherwise, your o2 is shot.

 

Yeah I see that now, you're right about that, thanks.

Could then the diverter valve be stuck(for some reason) air is only sent to the manifolds, would this mean the cats are not getting the oxygen they need and this is what is producing the high levels of hydrocarbons at idle?

And if they send air there, wouldn't this means the emissions now contain more oxygen which could in turn throw off the O2 sensors readings, making the ECM think the current fuel mixture is leaving too much oxygen, which prompts it to change the fuel mixture which then causes the high lambda values?

I'm not good with engines, I'm just guessing my way forward here.

 

What sort of scanner? I'm guessing this is something for the mechanic anyway, I just don't want to take the car back there again so soon after...
It can't be done just by putting your hand where the hose should be connected and feel for air flow?

What does BLM stand for?

And an O2 cross count? Again something for the mechanic *sigh*
Is this something expensive? Sure sounds like it.

 

Yes, you are right. If the ECM thinks it's sending air to the cat but a faulty diverter valve is sending it to the manifolds instead, the O2 sensors will read lean and the ECM will enrichen the mixture. That's how it works. And that's why the diverter valve needs to be working 100%. I think mine's going too because I'm running rich. I'll have to look into it soon.

 

Ok.. Tomorrow morning, remove the hose that goes TO the manifold. Put your hand over the barb from the diverter box and have a friend start the car. It should blow air.

Remove the hose to the CAT and put your hand over that barb. When the car reaches operating temperature, at one point, it should switch to that barb.

If not, the problem is a diverter solenoid.

Also a check valve could be bad. You can verify that by blowing into the tube yourself. If you can blow, its ok. If you cannot for the life of you, then the check valve is busted.

Quote:

What does BLM stand for?

And an O2 cross count? Again something for the mechanic *sigh*
Is this something expensive? Sure sounds like it.

Skip this, I assumed you had a scanner.

-- Joe

 

So what can be done with the diverter if this is the problem?

Also this prompts the question, why does disconnecting the hose coming from the cats lower Hc values? Is it because as someone said, it causes an exhaust leak, thereby fooling the sniffer?

 

Thanks alot for all the advice and help, thirdgen.org really is the best place for any kind of help, I get better advice from here than from my mechanic

What would one cost? Maybe it's something I could have use of in the future.

 

No, the one way valve should prevent that.

Does this car burn oil at all?

As far as a scanner goes, you could download software, and buy a cable and use a laptop. Or you can get a used scanner on ebay, or a new one at an auto parts store.. Expect to pay around $150 for a crappy scanner, $1500 for a decent one, and $35 for a laptop cable. (assuming you have a laptop).

-- Joe

 

Hmm well then the one-way valve mustn't work because I can feel a slight puffing of air coming now and then from the disconnected hose from the cats, I was figuring this was exhaust fumes.

Not to my knowledge no, it does have a slight leak I haven't bothered to fix because of the location of the leak and cost and work involved in replacing something so small.

What are these scanners called?

 

Could be vac on the exhaust. When it pulses, it might be pulling the check valve open to suck air in.

Quote:

Not to my knowledge no, it does have a slight leak I haven't bothered to fix because of the location of the leak and cost and work involved in replacing something so small.

What are these scanners called?

engine scanner, obd1 code scanner, aldl scanner, etc.


-- Joe

 

Ah, ok, here are the results of the emissions test by the way.
It also says a rich oxygen concentration distorts the exhaust values.

 

Someone told me to get rid of the smog pump entirely, it doesn't really help with emissions (or to pass the test)

The other thing that worked for me, was 1, use high octane, 2, use a methyl hydrate, 3, run the RPM really high prior to the test. I kept my rpm about 3K while waiting. In reality it overheated it just a bit. But it worked.

My emissions test consisted of CO, CO2 and HC, not O2...

 

what's lambda?

 

I had alot of problems getting my 92Z28 to pass emissions this year. I kept failing on Hydrocarbons. After doing a complete tune-up to include O2 sensor and converter I still failed. Was closer, not close enough. I took it to a mechanic and he told me my diverter valve was stuck and not working. He replaced it and I passed with no problems.

 

I've got an auto xray from summit for $175 that was very usefull. Granted it's no snap-on MT2500, but it gives me the information I needed to pass emmisions.

 

According to this site:
http://www.epicycle.com.au/electronics.htm

"...The Lambda is the residual oxygen in the mixture..."

"A Lambda value of 1.00 indicates a "neutral" mixture; higher numbers are leaner and lower are richer."

 

Didn't have anyone else here with me so I had todo it myself, put my hand over the whole and didn't feel anything, after a while I thought I might have felt a little, not sure.

Took it out for a drive and got it to normal temp and it was definitly pumping air, I felt that rather strongly, as opposed to when I was just starting it, maybe I ought to check if it starts pumping air directly to the cats and never to the manifolds, if it's stuck it can be stuck in that position as well, though I dunno why it would affect readings, except possily the O2 values.

Ah, forgot that, is there a difference if the car is turned on or not?

Just checked the tube to the cats, all clear, slight resistance but it was definitly clear.

I wonder, what effect could temperature have? I mean my car was standing there on the spot at the mechanics with engine idling for quite some time before the HC values and such went down, the engine got about twice as hot(100C instead of 40-60C on the oil temp) when not moving, could this be what got the HC values down, not the removal of the AIR tube?

 

222 to 21?? Was the car brought in hot? The hotter, generally the better you do on emissions, except NOx generally.

 

40 to 60 celsius(104-140F, 100C is 212F as well) if even that is usually all the gauge goes to when driving in this winter weather, if it stands still and idles it however becomes warmer, it was around 100 after a while at the mechanic, so I'm wondering if that was the reason they got the HC values down(or possibly both pulling out the tube and having the engine go warmer)?

I drove maybe 60 kilometers to go get the car tested and it was cold outside so I don't think the car was particularly warm at all, it seems to cool most efficiently in this weather.

 

Yes the temp will help lower the hc, particularly if the cat is cold.
You also may want to look at your timing.

 

Hmm well next time I go there I'm gonna stop a kilometer away or so and idle it and get it warmed up for a while before getting tested.

 

I'm hunting for new sparkplugs now, I found a good deal on some AC Delco's, but they weren't R45TS(standard) but R45TSX, it says the difference are that the R45TSX models are "pregapped for HEI ignitions"??

What does this mean? Also I hear that the R45TSX run hotter, is that good or bad? Will these fit my 1991 5.7l(350ci) V8 and if so would you reccomend them?

 

I did another test and the diverter valve is definitly bad because it's blowing air into the cats all the time, there where some instructions in the Haynes manual for that(6-12).

However I don't know what this "diagnostic terminal" they say I should ground is, the gist as I understood it was to remove the wire to the valve in question and use a test light on the contact with the ignition on.

However first I need a test light, just made my own with some wires, LED light and electrical tape, need to get a real one.

 

Well... changed the plugs, wires, cap and rotor and O2 probe, and it sure did work, the car even sounded and felt different than before. The HC values dropped from alternating between 100-290 to a solid 20 and maybe varying by 5-7 or so every now and then.