Check Engine Light, got code, now what? - Impala Tech
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post #1 of 2 (permalink) Old 04-05-2010, 08:32 PM Thread Starter
 
 
Join Date: Apr 2010
Location: Minnesota
Posts: 1
 
Check Engine Light, got code, now what?

First, I don't know a whole lot about cars, but am very mechanically inclined and can usually fix the problem with a little direction. My 2003 check engine light came on. It flashed when I am at higher speeds, like on the interstate. When to Autozone and got the code, P0302. Its a cylinder misfire on #2. Propable causes are:
Ignition system fault - spark plug(s), ignition, wires, coil
Vacuum leak
Injector fault
High or low fuel pressure

Other than changing plug and/or wires, does anyone have any recommendations or guidelines on further troubleshooting? Thanks.

Chris
Clothman97 is offline  
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post #2 of 2 (permalink) Old 04-06-2010, 09:57 PM
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Join Date: May 2009
Location: Mobile, AL
Posts: 82
 
Okay Chris, let's set the table first. A flashing check engine light means the misfire is severe enough to damage the catalyst in the converter if it is not repaired soon. Now, one easy way to tell if it is in the plug or wire is to switch them with a non misfiring cylinder and see if the problem moves with the components you moved (meaning it now sets a P0304 if you switched the plug and wire with #4). If you still get a P0302, it may be an injector issue. Swapping injectors is a major ordeal, so that is out. You need to see if you can get a shop to perform an injector balance test and that will tell you if #2 is flowing too much or too little when compared with the other cylinders. This also tells you the wiring to the injector is good, since you can control it with a scan tool to perform this test. If the injector tests ok, you need to look at mechanical issues. A couple of common things with this vehicle are vacuum leak at intake gasket (6.7 flat rate hours) or possibly a rocker arm bolt that is trying to strip the threads out of the hole on the cylinder head. That can be repaired with a thread insert. Unless you have access to proper shop manuals, once you get past the first couple of basics, I would recommend you get it to a reputable shop. You can end up costing yourself a lot of money in replacing good parts and possibly damaging something else on the car if you are not very familiar with late model fuel injection systems. Also stuff like 3.4 V6 engines having slightly different length pushrods for intake and exhaust valves that can easily be put in wrong. Good luck, but be careful....I know when something comes into my shop that someone has been working on at home previously, I command a premium because I usually end up having to undo what they have done before I can find and fix the actual problem (which usually ends up in that case being something very simple that could have been repaired for a fraction of what the poor guy has spent already on parts!)

ASE & GM certified master technician, and no, I don't think I know it all.
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