Passed smog but barely

[sandawgk5]

I just had to go get a smog test again, my every other year one, and I passed but my HC at the 15mph test were 119 PPM the max is 120. At 25mph the reading was 64 and max is 97. The rpm for both was between 1500-1600. The CAT is only about 2 years old and has maybe 500 miles on it in those 2 years.

The question I have is what could be causing my HC to be so high at low speeds but drop off at the higher speed even when RPM is the same?

If more info is needed I can post up the other numbers from the print out.

Oh timing is 1 btdc, 87 oct, temp was up around 190 and has a stock thermostat, and this is all on a bone stock 87 350 with about 180,000 miles on it.

Thanks

Dik

 

[4X4HIGH]

Was the truck nice and hot when you had it smogged? I don't mean water temp gauge but rather did you just start the vehicle and drive it a short distance then have it smogged or did you make a nice hard run down the freeway then take it in? The exhaust (Cat in particular) needs to be nice and hot for the 15mph numbers to be good. A brand new car will fail the test if the exhaust isn't hot enough.

 

[sandawgk5]

Was the truck nice and hot when you had it smogged? I don't mean water temp gauge but rather did you just start the vehicle and drive it a short distance then have it smogged or did you make a nice hard run down the freeway then take it in? The exhaust (Cat in particular) needs to be nice and hot for the 15mph numbers to be good. A brand new car will fail the test if the exhaust isn't hot enough.

I drove it about 12 highway miles from my house to the smog shop it then sat for about 20 min before they pulled it in. I thought about idling it until they pulled it in but did not.

The kid pulling it in stalled it a couple of times also due to the hydro assist and hydro boost brakes. He did not understand that steering does not like to be driven into the steering stops. The load on the PS pump would kill the motor.

Could that have caused the numbers to go up?

Dik

 

[dyeager535]

Steering loads the engine up but that shouldn't affect the reading unless it was being held against the stops while being tested.

 

[sandawgk5]

Steering loads the engine up but that shouldn't affect the reading unless it was being held against the stops while being tested.

Ok I didn't know if it would load up and then blow unburnt fuel into the cat.

Could the EGR be carboned up and clogged? I am not sure if the test just makes sure it is hooked up and gets the signal to open or if it actually measures the opening of the EGR.

Any other ideas?

Dik

 

[4X4HIGH]

I think your whole issue was that the CAT wasn't hot enough to effectively burn off any unburned fuel as it does when it is hot. You should have let the truck sit and idle at the least especially since you said it sat for 20 minutes after you got there.

 

[sandawgk5]

I think your whole issue was that the CAT wasn't hot enough to effectively burn off any unburned fuel as it does when it is hot. You should have let the truck sit and idle at the least especially since you said it sat for 20 minutes after you got there.

K thanks. In 2 years I will remember that.

Dik