Smog Advice

[Mtrotter]

I have a 98 toyota corolla that I use to beat around town, junk yard trips and such. I love the car, 42mpg and actually... the 1ZZ motor toyota put in it makes ok power for what it is.
Anyways, Its failing NO(ppm) readings at 25mph only. at 15 the reading are stellar! so for some reason the combustion chambers are getting too hot at higher speed but same rpm. I dont really get it.

Cat is new, o2 sensors are new. fresh oil change, fresh sparkys
Im going to put a new pcv valve in but I know it cant be that.

any words of wisdom? am I missing something totally stupid here?

[SVTfocus]

A bottle of this (http://www.autobarn.net/ch05063.html)

[oinojo]

I have a 98 toyota corolla that I use to beat around town, junk yard trips and such. I love the car, 42mpg and actually... the 1ZZ motor toyota put in it makes ok power for what it is.
Anyways, Its failing NO(ppm) readings at 25mph only. at 15 the reading are stellar! so for some reason the combustion chambers are getting too hot at higher speed but same rpm. I dont really get it.

Cat is new, o2 sensors are new. fresh oil change, fresh sparkys
Im going to put a new pcv valve in but I know it cant be that.

any words of wisdom? am I missing something totally stupid here?

check your tire pressures on the drive wheels.
PCV valve will help if you havent done it already.

how bad did it fail? please send me the numbers.

[70mustang]

My e30 was failing badly on NOx. Air cleaner, plugs and octane booster and it passed with flying colors.

[Mtrotter]

15mph
rpm-2726
Co2 - 14.66
O2 - 0
HC- 62 (64max)
CO(%) - .23 (55max)
NO(ppm) 87 (477max)

25mph

rpm 1840
Co2- 14.20
O2_ .69
HC 20 (47max)
CO-.02 (.54max)
NO-1865 (764max) Gross Polluter

I replaced the air filter, spark plugs, catalytic converter, up stream and down stream O2sensors, fresh oil.

Ill replace the PCV valve but I think a malfunctioning pcv valve would show elevated HC's due to oil in the intake.
I think a new pcv and ill soak the intake with carb cleaner, fill each cylinder with carb cleaner. run.. repeat...
change oil.. that might work. But The NO is high because it is running lean at the higher speed. Maybe its the carbon deposits causing that. I dont know.

what do you think Jonathan?

[Mtrotter]

oh yeah. I inflated the tires to 50 lbs

[oinojo]

you have an exhaust leak somewhere between the cat and the cylinder head. Your 02 reading should stay relatively close to 0 at 15mph and 25mph. Possibly a small leak at a gasket somewhere. I would check those new o2 sensors that were installed as they may still be loose.

[Mtrotter]

Thanks. I installed the O2 sensors tight, so that wont be it. I will remove the exhaust manifold when I get home from work tomorrow and inspect for cracks. I dont hear any exhaust leaks, but that dosent mean that there isnt a crack or failed gasket.
I kinda thought maybe The O2 levels were strange. but then again, I have never had problems at 25mph always the lower speeds when it came to NO with other cars.

Thanks, Ill let you know what I find

[froggy47]

oh yeah. I inflated the tires to 50 lbs


I'll bite, how does over inflating tires change any of the exhaust gasses?

[Mtrotter]

So, the theory behind overinflating the tires is this. With them fuller, firmer and rounder they will create less rolling resistance and this will make the engine work less. make sense? I dont know what kind of difference it actually makes, but the littlest bit can help sometimes

[Dov]

So, the theory behind overinflating the tires is this. With them fuller, firmer and rounder they will create less rolling resistance and this will make the engine work less. make sense? I dont know what kind of difference it actually makes, but the littlest bit can help sometimes

Is there something I'm not understanding? All the measurements are in parts per million (ppm). The "per" in there means it's the ratio bad gases to total gases from the exhaust. If an engine is not working as hard it is throwing out less total gases out the exhaust and that likely reduces the total amount of bad gases. However that does mean that the ratio has improved. The ratio is what they car measuring during a smog check. You're not trying to pollute less your trying to pass a test. I Would assume that some cars will create less unwanted gases per unit when they working harder because the exhaust will be hotter and burn excess hydro carbons better. I could be wrong though....

[froggy47]

I Would assume that some cars will create less unwanted gases per unit when they working harder because the exhaust will be hotter and burn excess hydro carbons better. I could be wrong though....


Mmmm, I was thinking along that line too when I asked the question, there is probably a "sweet spot" for each engine where pollution is minimized, however every vehicle is tested the same (with some exceptions like awd).

[nalbar]

Guys, sometimes


fuller, firmer and rounder

is its own reward.


nalbar

[oinojo]

I would check to see if you egr is working properly as well

[Mtrotter]

no egr

[Cullen]

Sounds like a good candidate for a race car.

[Larry]

If no egr, what's left is timing, then have the cat checked out.

[brian]

You could try taking it to a dyno shop and see what the AFR reading's going to be from the tail pipe at 25 mph. The reading from a dyno will typically be leaner than normal due to the catalytic converter. Or install a wideband yourself. My guess would be not enough fuel (fuel pump issue?) or unmetered air. Might want to check vacuum hoses too.