Well, after the new info you gave me, the IAC is probably not the problem.
If you have two glogged injectors, it could explain the misfiring code (P0300). How come the mechanics don't think the injectors are bad?
If you have two glogged injectors, you should have them cleaned or replaced and it should fix the misfiring problem (and possibly the P0420 as well since these 2 codes are likely related; now it could also be the other way around:a bad converter is responsible for the misfiring problem).
Here are some causes for a P0300 code:
Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
I would do the following:
-Find out for sure if you have glogged injectors. If so fix it/them
-Since one mechanic thinks there's a vacuum leak, he needs to do a vacuum test to confirm.
-test the converter. Test exhaust before and after converter (converter must be hot).
-If the other mechanic thinks you have a bad head gasket, he can test and find out for sure. Is your level of coolant low? Do you have excessive white smoke coming out of your tailpipe? Do you have coolant in your oil? If you pressure test the cooling system, does the pressure drop?
These are signs pointing toward a bad head gasket. If you have none of these, and the compression is good, and the car doesn't overheat, you probably don't have a blown head gasket.
-test your O2 sensors; if one is a little off, it could result in both P0300 and P0420 codes and may not trigger a O2 code.
Let me know how it goes.
Wednesday, September 24th, 2008 AT 11:12 AM