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Discussion Starter · #1 ·
I have been getting code 304 - misfire cylinder #4. 1304 is generic #4 and 1300 showed up a little latter. Cassette new. Plugs from dealership are new.
Can anyone tell me if a vacuum line could cause this? Broke check valve on vacuum line that comes off the right hand side of head. since no one seems to have a specific reason for this I am wondering if this could be it.
Also, have heard MAF could do it. Is there anything to look for? Lines appear to have good junctions and no holes. Ideas? TIA
 

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Check the charge air tube connections from the TB; check/clean the MAF, double check the gap on the plugs. Did you use NGK plugs? OEM or aftermarket DIC?
 

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Discussion Starter · #3 ·
OEM DIC, NGK plugs from dealer. Less than a year old. Will check gap but, switched #3 and #4 and it went away for a while. Does not happen below 70 degrees F.
Will check the charge air tube.
Do you have a suggestion on what to use to clean MAF, solvent? Acetone, Alchahol Carb Cleaner? TIA.
 

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I had the exact same codes. I retorqued spark plugs and moved them around. The code came coming back.

I got fed up and sent my injectors out for bench cleaning. Two of them were way out of spec. The fuel rail had lots of carbon build up on it too, so I cleaned it w/ intake cleaner...

In any case since they have come back, no codes.

This was in the middle of going from Chinese->OEM DIC too and back to NGK plugs, but after the switch the codes were still coming up. I was ready to give up.

I also cleaned my MAF (it was clean anyways), throttle body, and changed all my turbo hoses.

I also checked the fuel system pressure and had changed my fuel filter so that wasn't a problem.

Unfortunately the only way to know is to send the injectors out.

The car runs silky smooth now.

I also started putting real gas back in it (no ethanol). That was an immediate 3-4 MPG back. What a sham this ethanol is....
 

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Discussion Starter · #7 ·
As of this evening, my check engine light is off. Air tube was good. Bought the MAF cleaner and injector cleaner from parts store. Clerk suggested I double up on the Gunk injector cleaner. I did. I also sprayed down the MAF vigorously. Cleared the codes and took it on the highway. No light. Jumped on it a little and no light. I am skeptical.
As far as I know Murphy is still alive so, we or I, will see. Fingers crossed. Thanks for input. Injectors are next if this does not work.
 

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Don't double up on the injector cleaner (if you didn't already)if you're adding it to the tank; take it back or hold on to it and use it after your next 3 fill ups.

As of this evening, my check engine light is off. Air tube was good. Bought the MAF cleaner and injector cleaner from parts store. Clerk suggested I double up on the Gunk injector cleaner. I did. I also sprayed down the MAF vigorously. Cleared the codes and took it on the highway. No light. Jumped on it a little and no light. I am skeptical.
As far as I know Murphy is still alive so, we or I, will see. Fingers crossed. Thanks for input. Injectors are next if this does not work.
 

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Discussion Starter · #9 ·
I dumped both in the tank. Spoke with parts guy and he said it would be OK. I know, I know.
I called Gunk and spoke with their tech. He said it will not do any harm....
 
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