p300 misfire

[radioralph]

2000 Silverado,2wd,5.3,111k miles. I purchased truck Oct 2002 with 84k highway miles,running hours were very low.Truck well serviced past three years,fuel filter every 10k,plugs and wires replaced with GM parts at 95k,egr valve at 90k,throttle body serviced with 3M products at 96k,cooling system serviced 1 year ago,trucks SES light came on and I noticed a slight stumble, the truck had been running approx. 2 minutes and SES came on while backing,I did not notice the SES blinking,after several stop/start cycles the light went off.IN the last 150 miles the SES has came on two more times and I have not noticed any blinking of the light. Fuel pressure is 60 psi,only code is p300,tester shows a continuning misfire on cyl 2 and 7 ,with most misfire occuring on 7. Ran injector test on all injectors and all tested the same except 7 which the test indicated a slightly clogged injector...What do you suggest I do next?

[GM-Tech]

The rear most injectors (mostly #7) have a tendency to pick up the crap that's in the fuel lines. #7 because the fuel enters on that side before going over to the right side, and because of the tilt of the engine, gravity tends to help debris to end up in #7.

 

If you pull the injector and turn it upside down and tap it on a piece of white paper, you'll probably see a bunch of black particles come out of it. If you put a magnet to the "dirt", you'll see that it's magnetic. That's because that is rust not dirt.

 

Of course, attempting to clean the injectors first might be the easiest first step. By this I mean pressurized injector cleaner though the fuel pressure tap, not by adding anything to the tank, which won't do squat. If it's a dirty pintle problem, this would probably fix it. If it doesn't fix it, I'd pull the injector and check for what I said.

[radioralph]

Thank you for your reply.If I replace a injector,is there a improved injector that you recommend,and am I assuming correctly that I only need to replace the bad injector and that any improved version will work along with the other existing injectors?

[GM-Tech]

I don't know of any updated design from GM. You'll get what you have in there now, as far as I know.

[radioralph]

The rear most injectors (mostly #7) have a tendency to pick up the crap that's in the fuel lines.  #7 because the fuel enters on that side before going over to the right side, and because of the tilt of the engine, gravity tends to help debris to end up in #7.

 

If you pull the injector and turn it upside down and tap it on a piece of white paper, you'll probably see a bunch of black particles come out of it.  If you put a magnet to the "dirt", you'll see that it's magnetic.  That's because that is rust not dirt.

 

Of course, attempting to clean the injectors first might be the easiest first step. By this I mean pressurized injector cleaner though the fuel pressure tap, not by adding anything to the tank, which won't do squat.  If it's a dirty pintle problem, this would probably fix it.  If it doesn't fix it, I'd pull the injector and check for what I said.

 

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[radioralph]

I don't know of any updated design from GM.  You'll get what you have in there now, as far as I know.

 

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I removed and cleaned all injectors and fuel rail and reinstalled,also changed fuel filter....problem resolved... Thank you for your reply,Mr. G.M. Tech....