Just got smogged... High on HC

[Skandocious]

So I just got Bertha smogged and she did well except for the 15mph test on the HC-- passed by only 2 PPM. Here's the report:

From what I understand, this means I'm running a little lean. Is this a telltale sign of any specific problem or do I need to start hunting? It shouldn't be that high-- it used to always pass with flying colors.

Cats are new in the past couple years (Magnaflow), spark plugs are brand new (Motorcraft coppers gapped to somethin' like .055), O2 sensors are new Bosch units replaced a couple years ago...

 

[Truckin4life]

broken vac line?

 

[Blue Goose]

broken vac line?

Well that would certainly go with the air conditioning messing up. Good call, Don!

 

[Truckin4life]

Brad ill agree with you, if he finds a broen line, skank is it possible the modulator is cracked by chance? Just a guess...

 

[Skandocious]

So a broken vac line could give a lean condition?

And what's a modulator?

 

[73F100Shortbed]

Yes a broken vacuum line can give a lean condition.

 

[Skandocious]

Can we deduce anything from the fact that I was a lot lower on HC for the 25mph test than the 15mph test?

 

[smokey]

Your rpms were a bit high creating a bit more vaccum masking the leak a little more causing the lower reading.

 

[Truckin4life]

Hmmmmmm....

I'm not sure, but I would guess its still a vac leak but on something unvital to the engine.
Really its a stab in the dark...

 

[73F100Shortbed]

Your rpms were a bit high creating a bit more vaccum masking the leak a little more causing the lower reading.

 

[Skandocious]

Well I was talking about how the vent's switching in the cab recently got a lot worse and the other day I noticed a pretty loud and constant hiss in the cab right behind the vent controls... You think a moderate sized leak inside the cab could be large enough to affect the engine?

 

[Blue Goose]

Absolutely!

 

[5.0Flareside]

all vacuum is basically somehow connected to the engine...

 

[Skandocious]

Well I understand it's all in the same place but it seems like such a small leak shouldn't affect engine operation.... Guess I'm wrong. I'll investigate.

 

[73F100Shortbed]

Yes even a small leak can cause an issue.

 

[Skandocious]

K. I'll investigate tomorrow. Thanks guys.

 

[Truckin4life]

Chris, please go back to the thread and look at my reply.

 

[Skandocious]

You're talking about how your leak was behind the passenger kick panel? I'm almost certain my hissing was coming from directly behind the control knobs in the dash.

 

[Truckin4life]

Behind the dash and the kick panel.

 

[Skandocious]

So I just took apart my dash and put my ear to the back of the control panel (where the 3 knobs are) and the hissing noise is definitely coming from the back of the mode selector switch. But all of the vac lines are nice and bendy and healthy, and secured properly to the back of the vac switch. The 5 vac lines connect to a rubbery piece which is affixed to the plastic vac switch via 2 nuts, and if I pressed really hard on the rubbery piece and squeezed it against the plastic the hiss would go away.

Is this normal behavior? I can't help but wonder if maybe it's supposed to hiss when the switch is in the OFF position. As soon as I switch to vent, the hiss goes away... Any help?