Quote Originally Posted by whitefish
Thanks petrified.rabbit:

I put in regular NGK V-Power - not iridium. My 2005 had stock regular AC Delco's, not the Delco Iridiums recommended in the owner's manual.

Note again that I have a K&N drop in filter that was installed April 2009 and cleaned in November 2009 (just before winter).

The CEL has never come on. That said, I plan on testing the O2 sensors using a multimeter using a onboard/in situ method.

I believe I have tested the IAT with a multimeter. I had a good "How To", but I didn't have a volts to temperature reference to use for a conclusive test. All I could measure was whether there was a "reaction" and the reaction rate in the IAT. I assumed the IAT is the only sensor on the air intake tube (after the air cleaner box).

I couldn't find a MAF sensor on the Aveo.

I did not test the coil pack. How would I do that?

Would a compression test be they way to find bent/leaky valves? How would I test for a plugged CAT, other than smell? My understanding is that a bad CAT would smell like rotten eggs all of the time, no? Would the following be advisable?

"When a clogged converter is suspected, some mechanics temporarily remove the O2 sensor from the exhaust pipe ahead of the catalytic converter and look for a change in performance."

Thanks!
its tough replying to long posts on an iphone..

1. i am not sure if the iridium plugs matter or not, i believe the later cars have regular ngk's in them? but i have the ecotec, not your engine so i have not personally verified that.

2. K&N drop in filter should not limit the system. but over oiling it can be restricitive, and REALLY over oiling it can foul plugs. But your talking winning the lottery odds there.

3. if there is no check engine light that means the problem might not be consistent enough to switch the light on. This is where knowing more about the daewoo computer would come in handy, typically its 2-3 occurrences in a row throws the light, then 3 without will shut it off. But the parameters of the signal might be within spec, but enough to cause fuel consumption problems.

4. The IAT sensor (i dont have this either) if it fluctuated it is probably ok if the range was acceptable, i believe typical failure results in an open circuit or high resistance.

5.You do not have a MAF but you have a MAP sensor, its kind of an indirect way of doing what the MAF does. it just reads vacuum instead of flow. Check that, and the vacuum lines for leaks.

6. I do a relatively old way of testing the coil pack and wires. start the car and mist them with water from a spray bottle. If there is a problem, you get a light show. just don't overly wet anything else and it is perfectly safe.

7. a compression test or cylinder leak down would be good for checking valve, most likely they are still ok though, running on 3 cylinders would be very noticeable.

8. that method to test for cat clogs works if the engine wont start at all from a totally clogged cat. it wont tell you too much since it runs, you would need to compare o2 sensor signals, or take of the cat and look through it.