2001 Suburban 1500 5.3, P0304 drives fine but idles like it has a big cam. SES on and sometimes flashes. I put in a new plug, swapped coil from 4 to 6, and spark plug wire from 4 to 2, cleaned the MAF and cleared the codes.


No change. After a while at idle (like at the end of a traffic light cycle) the SES light flashes until I start to accelerate and then goes out. Scan shows a pending code P0304.


I listened to the fuel injector and it sounds like the other ones on the bank, but I know that won't tell me if it's dirty.




Any thoughts on what to tackle next? I thought swapping all of the spark parts would tell me something. I'm surprised I still get a #4 code.

 

Check into knock sensors failing, giving wrong info. Or intake gasket cracked allowing extra air into that area.

My 02 has a similar issue not as extreme. My one knock sensor is corroded- didn't have the money to fix at the time when I did the intake gasket

 

Have to swap injector to be sure.

 

I changed knock sensors and intake gaskets about 15k ago. That gave knock sensor errors.


Swapped injectors and still not good. P0304 code came back but I've cleared it a few times and it hasn't come back. But coming down to idle at a red light - like at 1 MPH - it gets very surgy-rough and then a lumpy idle. Start rolling at the green and accelerating and it smooths out. No driveability issues. Going to do a compression test tomorrow - any other ideas?

 

possibly needs a tune adjustment for the idle tables.