Failed Smog - Any Clue in the Numbers?

My car failed the California smog check today. I talked with three mechanics in town about my repair options, and all three tell me I need to buy the diagnostic package and see where we go from there.

I suppose it's to their credit that they decline to offer a firm diagnosis on the basis of the smog numbers, but I would have more confidance in a mechanic who could tell me the most likely cause of the failure. I have to beleave that the emission test results themselves tell a big part of the story. Maybe I'm off base here, but I need to make a fix-it or junk-it descision. That descision might be easier to make before spending that first $100.

The car is an '89 Daihatsu Charade 1.0L with 250K on it (100K since new rings and 40K since new catalytic converter). It has new plugs/wires/distributor cap and rotor, but no adjustments have been made since the last smog check two years ago.

There is an unusual symptom that mey be related. Lately there has been a problem with the idle speed dipping too low after suddenly removing load, often leading to stalling at stop signs. This is mostly a problem on warm days and after the engine is hot from long freeway runs. The idle speed quickly comes back and it idles fine after that.

My emission numbers are:

15 MPH Test 2068 RPM CO2 14.2% O2 0.6% HC 41 PPM (147 Test Limit) CO 0.70% (0.88 Test Limit) NO 986 PPM (889 Test Limit)

25 MPH Test

2247 RPM CO2 14.6% O2 0.2% HC 27 PPM (122 Test Limit) CO 0.53% (0.78 Test Limit) NO 1147 PPM (829 Test Limit)

If anyone can offer some insight into these numbers, I would appreciate hearing. Thanks.

Reply to
Blake
Loading thread data ...

Unless I have missed the boat totally, everything looks okay except your oxides of nitrogen numbers.

High NO should indicate excessive temperature in the combustion chamber, which -generically- can come from several sources...failure of the EGR system, lean operating conditions, spark timing off, or other things that would result in high combustion temperatures. Lots of things can affect this.

Maybe somebody knows more about the specific Daihatsu unit.

Reply to
<HLS

Thanks for the tips. This was very helpful.

After reading them, I did some checking. The bottom line (so far) is that the engine idles normally with the EGR valve removed and a big gaping hole in the intake. I suppose it must be plugged with carbon.

I can see a couple of knock-out plugs on the EGR passages on the intake plenum. I guess I'll knock them out and see how much carbon I can clean out. Beyond that, is there anything else? Any magic solvent that cleans out the carbon from those hard-to-reach places?

Reply to
Blake

Well there is a way to remove some of the carbon BUT if the passage is blocked it probably won't remove it all.

Hit a GM dealer OR a GOOD parts store and grab a bottle of GM Top Engine Cleaner (liquid not the spray can version), the proper amount of the correct oil for your vehicle and a good filter.

If you live in a crowded area go visit an open area or do this at night. It WILL generate a LOT of smoke and whatever the exhaust is pointed at is going to get REALLY crappy. DON'T do this procedure INDOORS.

Then run the engine till it hits operating temperature and shut it off.

Disconnect the air intake hose from the intake manifold IF it is after the MAF sensor, if not find a vacuum line and disconnect it. (power brake booster line works pretty good on most vehicles) On your engine you can also pour a small amount into the EGR passage.

Start engine. It may run crappy but don't worry about it.

Slowly pour half the bottle of cleaner into the intake connection. Keep the engine running while you do this. If you need to use a vacuum line just stick it into the bottle halfway and let the engine suck it up.

Now dump the remaining half bottle into the intake connector. If your using the power brake line just use a funnel and dump it in quick.

This should shut the engine down,(if you used a small vacuum line shut it off). Allow the engine to sit and the cleaner to soak for 15 minutes or so.

Reconnect the air intake or the vacuum line. If this is a newer vehicle you will likely set a code or two doing this.

Start it back up and watch the cloud of smoke form... Then jump in and take it for a spirited drive to blow out as much crud as it can. Just be prepared for people to yell that your vehicle is on fire! Did I mention that this stuff makes a LOT of smoke?!

As soon as you get back change your now VERY dirty oil and filter.

Reply to
Steve W.

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.