emissions help?

[waterpirate]

So the 87 tbi heavy chevy failed inspection today, 20 points high on c02. Any suggestions before I send it to the shop and get a 200.00 waiver? It seems to idle a little high, and has the OG catalytic converter. Other than that it runs ggggrrrreat! Except for todays fail.
Eric

 

[Vbb199]

Map? Cts?
Either of those not functioning properly can cause a rich condition.

Cts readings has alot of say in afr on the tbi trucks

 

[waterpirate]

Thanx for the reply. I am digging into it as we speak. lol
Eric

 

[Vbb199]

Thanx for the reply. I am digging into it as we speak. lol
Eric

There is voltage tests you can do for both the MAP and CTS with a multimeter.

You can test the map's signal wire by turning the key "on" you should have 5 volts on the power input, and the signal.

Turn the truck on, the signal wire for the map i believe should be at 1v output then, the power input still remains the same, (5v)

You can also do the test with a handheld vacuum gauge and pump the map sensor up to 20-22 in/hg with the key in the "on" position. Yeilds the same result.



The CTS, i cant remember the proceedure. It involves resistance i believe.

 

[SquareRoot]

E-Rod

 

[Vbb199]

@waterpirate

I think you are supposed to see 330 ohms of resistance at operating temps (180°) at the CTS

 

[waterpirate]

E-Rod

Where exactly is that?

I am going to chase the volts tomorrow. The other clue is that is swilling fuel???
Eric

 

[Paladin]

E-Rod

WHAT??? No LS swap! LOL

 

[Turbo4whl]

Couple of tricks if you are trying to pass a 2 speed idle test. Especially good if you are only missing the test by a few points.

Engine oil collects hydrocarbons. Change the engine oil right before the test. The PCV valve sucks these hydrocarbons back into the engine. Better still is pull the PCV valve out of the valve cover and let it suck fresh air instead of crankcase fumes. Of course the inspector may be looking for this.

Second trick is retard the timing. You can hide this easy by pulling the vacuum advance hose off the distributor. Push a plug in the hose, and put it back on the distributor advance.

PS: I didn't tell you any of this.

 

[Ricko1966]

How old are your plugs, cap and rotor?

 

[skysurfer]

How many miles on the odometer? My original cat was a burned out shell at 130k. An aftermarket replacement made a huge difference but they don’t last long. The second replacement was installed with flanges welded on each end and it only gets installed at test time.

 

[SquareRoot]

WHAT??? No LS swap! LOL

Emissions legal LS swap for those poor california folks.

 

[waterpirate]

Cap, rotor, plugs, have less than 500 miles on them. Same with the oil. Cat converter has over 200k on it. Besides al the rest of the weirdness I had 2 tests yesterday. First test I drove the truck to get gas 3 miles, 1 mile to test, waited 10 minutes to get tested at idle and got a 243 ppm, 220 needed. Second test I drove it around all day and ran it hard down the road for 30 minutes prior to test. Waited in line at idle 30 minutes to get test and got a 565ppm. Obviously sitting at idle is bad for the test lol.
Eric

 

[Vbb199]

Cap, rotor, plugs, have less than 500 miles on them. Same with the oil. Cat converter has over 200k on it. Besides al the rest of the weirdness I had 2 tests yesterday. First test I drove the truck to get gas 3 miles, 1 mile to test, waited 10 minutes to get tested at idle and got a 243 ppm, 220 needed. Second test I drove it around all day and ran it hard down the road for 30 minutes prior to test. Waited in line at idle 30 minutes to get test and got a 565ppm. Obviously sitting at idle is bad for the test lol.
Eric

I still vote one of the two sensors, its causing a rich condition, which explains your slightly higher idle.

 

[Vbb199]

@waterpirate whatever became of this?