P0300 03 sierra 6.0

[53boy]

I have a 03 GMC Sierra 6.0 . Keeps throwing p0300. Now I am still not so good understanding all of these numbers but I took these numbers off the screen on my scanner freeze frame data from when the problem occurred. 

 

Pic And here’s the list of the rest

 

Engine speed rpm 2569

Vehicle speed mph 73

Abslt tps% 35.7

 

any help would be great thank you

[Doug_Scott]

That trouble code means too many misfires.  Is that the only code get, or are you also getting other codes? What have you already tried doing?  

[53boy]

36 minutes ago, Doug_Scott said:

That trouble code means too many misfires.  Is that the only code get, or are you also getting other codes? What have you already tried doing?  

That’s the only code , other than a p1516 which I also have to look into.

 

just bought the truck. Did a tune up today to find out plugs and wires are pretty new. Had Delphi 7mm wires, and Bosch platinum gap .060, replaced with ngk iridium .040, ran rougher and put the Bosch plugs back in. Also put new ac delco wires on

 

air filter new. Fuel filter new.

[Doug_Scott]

22 minutes ago, 53boy said:

That’s the only code , other than a p1516 which I also have to look into.

 

just bought the truck. Did a tune up today to find out plugs and wires are pretty new. Had Delphi 7mm wires, and Bosch platinum gap .060, replaced with ngk iridium .040, ran rougher and put the Bosch plugs back in. Also put new ac delco wires on

 

air filter new. Fuel filter new.

That code is for the TPS.  Do a search for a TSB on the throttle position sensor, I am old and don't recall the details of it, but do remember hearing about it.  If your truck is supposed to use a gap of 0.040 you should use that gap.  You may also, want to try disconnecting battery for a couple of minutes to get it to relearn again after changing the plugs back to what it is supposed to be running. 

While plugs are out do a compression test.  It would be good to know what condition the engine is in, especially when trying to correct multiple misfires. 

[53boy]

29 minutes ago, Doug_Scott said:

That code is for the TPS.  Do a search for a TSB on the throttle position sensor, I am old and don't recall the details of it, but do remember hearing about it.  If your truck is supposed to use a gap of 0.040 you should use that gap.  You may also, want to try disconnecting battery for a couple of minutes to get it to relearn again after changing the plugs back to what it is supposed to be running. 

While plugs are out do a compression test.  It would be good to know what condition the engine is in, especially when trying to correct multiple misfires. 

Gotcha thanks . Just want someone who can read this freeze frame to point me in the right direction 

[Jsdirt]

Nothing out of the ordinary on the freeze frame that jumps out at me.

 

If you have your plugs gapped at .060", set them to .040".  .060" is just asking for a burnt up coil, regardless of manufacturer specs. The voltage required to jump that gap under compression pressure is VERY high - lots of unneeded stress put on the ignition system, namely the coil.

[mjm-1957]

Does your scanner have a misfire graphic display or a misfire counter for each individual cylinder? The Tech 2 has both and can be very helpful in pinning down a cylinder causing the misfire.Does the check engine start flashing before setting the P0300?Would be helpful to know if its one cylinder, one bank or all cylinders.

[Jsdirt]

99.9% of the time, an 0300 is multiple cylinders, not just one or two, or one bank.

[mjm-1957]

https://screenshots.firefox.com/w33kf9quGw7ykqGt/gsi.ext.gm.com

[Jsdirt]

Exactly what I just said. Random, multiple misfire. Yep - raw fuel will melt the cat - light will flash in that instance.

[txab]

On 8/18/2018 at 9:53 PM, Doug_Scott said:

That code is for the TPS.  Do a search for a TSB on the throttle position sensor, I am old and don't recall the details of it, but do remember hearing about it.  If your truck is supposed to use a gap of 0.040 you should use that gap.  You may also, want to try disconnecting battery for a couple of minutes to get it to relearn again after changing the plugs back to what it is supposed to be running. 

While plugs are out do a compression test.  It would be good to know what condition the engine is in, especially when trying to correct multiple misfires. 

Correct! GM issued a gap change around 2007 for vehicles back to 99 and 98 in some instances. If you reinstall the .040 plugs do as suggested and disconnect the batt. cables for a bit so as to force the ECM/PCM to begin the re-learn process

 

Also, check for vacuum leaks on intake especially intake to block gaskets. Quite common to leak

[53boy]

On 8/19/2018 at 6:05 PM, mjm-1957 said:

Does your scanner have a misfire graphic display or a misfire counter for each individual cylinder? The Tech 2 has both and can be very helpful in pinning down a cylinder causing the misfire.Does the check engine start flashing before setting the P0300?Would be helpful to know if its one cylinder, one bank or all cylinders.

Check engine light did flash only once when I was doing 85mph for about 15 miles highway. 

 

I do not have a tech 2 scanner wish I did. I really want to smoke out the engine and see if it possibly a intake leak. Would have no problem doing intake gaskets 

[Jsdirt]

1 minute ago, 53boy said:

Check engine light did flash only once when I was doing 85mph for about 15 miles highway. 

 

I do not have a tech 2 scanner wish I did. I really want to smoke out the engine and see if it possibly a intake leak. Would have no problem doing intake gaskets 

No need for a Tech 2 - Autel & Launch, just off the top of my head have that capability.

 

Get empty bottle of water, soda, whatever, fill it with WATER, & poke or drill a hole in the cap - 1/8" is plenty - fire it up cold, and squirt all along the head/intake junction. If there's a leak big enough to throw a random, you should either hear it, or notice a change in engine RPM when the water hits it. I've heard a few engines slurp when the water hit, the leak was so big. 

[53boy]

3 hours ago, Jsdirt said:

No need for a Tech 2 - Autel & Launch, just off the top of my head have that capability.

 

Get empty bottle of water, soda, whatever, fill it with WATER, & poke or drill a hole in the cap - 1/8" is plenty - fire it up cold, and squirt all along the head/intake junction. If there's a leak big enough to throw a random, you should either hear it, or notice a change in engine RPM when the water hits it. I've heard a few engines slurp when the water hit, the leak was so big. 

I have a crappy autel but it does some stuff . Not so sure about viewing each cylinder . Should probably figure that out though

 

plan on taking the truck to shop and get a smoke test done on it . 

 

Also guys i have a p1516 electronic throttle body code

 

truck makes a whistling noise seems to be coming from throttle body for whatever reason. Only happens randomly but more so In the morning and it’s never consistent , only some days. Idk lol. Truck runs and drives fine honestly imo , still tons of power and mpg is fine 

[Jsdirt]

The Maxisys is the good Autel - just as good as any Snap On unit, although it doesn't have a service similar to SureTrack ... but it's over $8,000 cheaper.

 

No need for a smoke test - just do the water test right in your driveway. Quick, easy, and FREE.

 

For the P1516, do a tug test on the wires going into the throttle body. Don't yank the pee out of them, but just a firm tug. If any of them feel "stretchy", and pull farther out than the rest, you've found your problem. The wire breaks inside the insulation, so you can't see it.  If that checks out, make sure the connector pins (both male in the unit, and female in the plug) aren't green & crusty, or the connector itself isn't full of water. Common issues.

 

Never thought I'd see a day where auto manufacturers would build wire jacketing that's stronger than the copper strands inside ... but I digress .