Hmm, little puzzled on the SMOG test results!!!

[alia176]

I failed the first SMOG test due to "visual smoke". Ok, fine. Maybe the wife didn't run the car hard enough before taking the test. Her HC and CO were well within the limits.

In NM, once you failed the test at a private Air Care station, you can get free testing at the City Air Care station for free so off I went for another test.

BTW, this is the first time this car didn't pass SMOG!

test #1: failed due to visual smoke

idle 662 rpm, CO actual: 0.33, CO limit: 1.20
rev 2550 rpm, CO actual: 0.30, CO limit: 1.20

idle 662 rpm, HC actual: 120, HC limit: 180
rev 2550rpm, HC actual: 75, HC limit: 180

test #2: idle test only, failed due to high HC and CO.

idle 602 rpm, CO actual: 1.35, CO limit: 1.20
idle 602 rpm, HC actual: 409, HC limit: 180

What puzzles me is why the numbers are so drastically different between the two tests, about two weeks apart? The only thing changed was a fresh tank of premium fuel.

Things done to the car few months ago:
timing belt project
front engine re-seal project
replace all coolant and vacuum hoses
replace knock sensors (preventative maint)

This one is a head scratcher.

Test #1


Test #2


So, I wonder where do I go from here!

Thanks for any inputs.

[SomethingElse]

Differences such as those could easily be explained by a difference in temperature of the engine and or catalytic converters during testing.

[svxistentialist]

I reckon by the look of those two tests your wife drives a heck of a lot harder than you do!



More seriously though you seem to be failing on idling figures.

Is your mileage high? I'm presuming it must be, smoke visible generally means worn rings. Faced with this problem there are additives you can use that do a good job, you might consider using one for the next test.

Your idling figures can be bad for a number of reasons not really related to the things you recently fixed. These would be:

IAC, Idler Air Control valve and solenoid. The solenoid would throw a code if faulty, but you might consider using Sea Foam on the butterfly to ensure it is clean from carbon and gunge.

AFM, the Air Flow Meter. If this is dirty [check how clean your air filter may be and replace as necessary] you can clean it, do a search for instructions.

TPS, the Throttle Position Sensor. These can develop a "bad spot" and not read linear voltage across the spot where normal driving takes place, from wear. Trevor has a good test in the how to. Don't rush to replace unless it's faulty, the little bugger costs over 100 bucks.

Plugs/Coils. If these are faulty they will be affecting the timing. If you are on original plugs and over 100K miles, replace them. Coils can go bad through the insulation breaking down over time. You would need to troubleshoot this if it's a problem. They also are expensive to replace.

If you are having an intermittent fault in the timing you will experience a shudder or stumble in the engine as the car ticks over. if it's doing this then one or more of the cylinders are misfiring, and the misfire will pollute your gas analysis figures. You need it to be ticking over absolutely smooth.

Hope one of these helps. Work from the cheapest fix up.

Joe

[alia176]

thanks for the info, Joe. Yeah, guess my wife has a lead foot

Anyway, the intake path is very clean as I just did the timing belt service recently. The intake manifold was removed and cleaned thoroughly with elbow grease and serious caustic fluids.

The engine is showing no signs of anything, not even a stumble, funny sounds, etc. The smoke that the first inspector saw could not be repeated with the second inspector so I don't quite know what's up with that.

With that said, I'll clean out the MAF sensor. I don't see any need to mess with the TPS as it isn't giving me any trouble. Car accelerates great, no dead spot, idles fantastically and so on. Good call on the plugs but they're very young in terms of mileage. The car only has 120k miles so she doesn't get driven all that much. I'd estimate the plug to be around 18k miles old. Per your suggestion, I'll check out the Idle air circuit and air path for anything obvious.

The trouble with the SMOG test machines in NM and the SVX's is that they don't have a good way to detect engine speed. There is no spark plug wire for an inductive pickup. They use this gismo that picks up cyclic vibration from the engine and depending on its placement, their machine can show an idle range from 300 to 2400 rpm while the engine is actually idling steadily.

Thanks again for the suggestions, much appreciated.

Originally Posted by svxistentialist

I reckon by the look of those two tests your wife drives a heck of a lot harder than you do!



More seriously though you seem to be failing on idling figures.

Is your mileage high? I'm presuming it must be, smoke visible generally means worn rings. Faced with this problem there are additives you can use that do a good job, you might consider using one for the next test.

Your idling figures can be bad for a number of reasons not really related to the things you recently fixed. These would be:

IAC, Idler Air Control valve and solenoid. The solenoid would throw a code if faulty, but you might consider using Sea Foam on the butterfly to ensure it is clean from carbon and gunge.

AFM, the Air Flow Meter. If this is dirty [check how clean your air filter may be and replace as necessary] you can clean it, do a search for instructions.

TPS, the Throttle Position Sensor. These can develop a "bad spot" and not read linear voltage across the spot where normal driving takes place, from wear. Trevor has a good test in the how to. Don't rush to replace unless it's faulty, the little bugger costs over 100 bucks.

Plugs/Coils. If these are faulty they will be affecting the timing. If you are on original plugs and over 100K miles, replace them. Coils can go bad through the insulation breaking down over time. You would need to troubleshoot this if it's a problem. They also are expensive to replace.

If you are having an intermittent fault in the timing you will experience a shudder or stumble in the engine as the car ticks over. if it's doing this then one or more of the cylinders are misfiring, and the misfire will pollute your gas analysis figures. You need it to be ticking over absolutely smooth.

Hope one of these helps. Work from the cheapest fix up.

Joe

[alia176]

I returned to the same facility yesterday and it passed! I didn't do a damn thing.

Here're the #s:

Test #3:

No visible tail pipe smoke. I suspect that the original inspector saw water vapor.

idle 626 rpm, CO actual: 0.01, CO limit: 1.20
rev 2550 rpm, CO actual: 0.01, CO limit: 1.20

idle 662 rpm, HC actual: 30, HC limit: 180
rev 2550rpm, HC actual: 27, HC limit: 180

Same tank of gas as test #2.

[svxistentialist]

Good result!

Water vapour is probably a good call. The SVX makes loads of it.

Either they have flaky test machines or they don't know their job or a bit of both.

Joe