I have a 91 Camry LE with 180K miles. It recently failed the HC portion of the Texas emissions test. As this is often caused by misfiring, I connected my inductive timing light to each of the plug wires. I found that there was a patterned miss in each of the wires. This lead me to believe that there is a problem with the distributor. My question is "What should I do next to find the problem?". BTW, I changed plugs and wires last year when I passed the emissions test. I would appreciate any suggestions.
In news: snipped-for-privacy@news.hal-pc.org, Al Kondo being of bellicose mind posted:
An inductive timing light is NOT a reliable indicator for locating a misfire. Many inductive lights don't work reliably with high resistance high tension wires and can be influenced by which way the inductive clip is placed over the high tension wire (many have a direction arrow on the clip).
Elevated HC that is due to misfire and will also have lower than normal CO levels because .... CO is a byproduct of combustion. No combustion, no CO. With normal CO and elevated HC, look for excessive base ignition timing. BTW, you did not mention what the CO reading was. That would be helpful. A very low CO with elevated HC suggests excessively lean idle (vacuum leaks).
It was mentioned that my problem could be excessive base ignition timing. I am not sure what is meant by this. Does this mean that the timing is too far advanced? Please clarify.
Also, here are my HC and CO readings from my emissions test: (the standard or passing reading is in parentheses)
Hi Speed Low Speed
HC (ppm) 207 (123) 415 (128)
CO (%) .41 (.69) .67 (.71)
Would these readings indicate that the fuel is inadequately combusted or that there is a timing problem. By the way, my NOx were well within acceptable range. I would appreciate thought about this.
In news: snipped-for-privacy@news.hal-pc.org, Al Kondo being of bellicose mind posted:
"Excessive base ignition timing" simply means the ignition timing when set at idle is possibly too far advanced. Put the jumper wire in place as mentioned on the EPA sticker under the hood and recheck "base timing."
If your NOx levels were well within range, then we will assume EGR system is functioning correctly although.... too much base ignition timing will raise NOx readings depending on engine load. Also, if there was a CO2 (carbon dioxide) reading on your smog ticket, the higher the CO2, the better .... indicating greater exhaust catalyst activity.
The readings are the result of exhaust taken AFTER the catalyst instead of ahead of the catalyst so diagnosis is a bit more difficult. ASSUMING you find the ignition timing to be correct, the next items to check are for really filthy (gasoline diluted) engine oil, a failed O2 sensor, and finally a failing exhaust catalyst. O2 sensor life spans vary by a wide range in real life. Some fail by
50k miles while others may last 250k miles. It's all in the gasoline quality and driving habits which vary a lot by region. Same to be said for the exhaust catalyst.
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.