P0300 update!

[vncj96]

So I FINALLY broke that O2 sensor lose, put the new one in and cleared the code. Started the truck up and drive it around for a bit and no problem. The wife got home, we went to the store and when i started it up again it was back. So I have replaced plugs, wires and the O2 sensor. My next step will be the fuel filter and the coil. Just to add I do notice that it does idle a little rough and its idle is around 500-600 RPMs. If the sterring whell is turned the truck almost want to die, but if you give it some gas and get the RPMs up to 800-900 then everything smooths out.

[Jimmiee]

Before you throw a fuel filter and coil at it why not check your freeze frame data on that P0300? This may lead you in the right direction. If your truck runs good when you floor it, your coil and fuel filter are working just fine.

[vncj96]

What is freeze frame data, all I have is a hypertech programmer that can read the codes, I assume I will have to take it to the shop to do this

[TRPLXL2]

No you don't have to take it to the dealer for freeze frame data, I have an Auto X-ray that does the freeze frame data and it is awesome. You would need some kind of medium range diagnostic tool such as an Actron, Auto X-ray or some other brand, I paid almost $600 for mine but they go as low as $150 and you could have freeze frame. Basically you would need someone to drive the vehicle while you have the scanner plugged into the OBD II port, and then there is a whole process that you go through and it will trap a ton of data that you can look at afterwards.

I will see if I can download my freeze frame info for you to see, I just did this for my S-10 so give me a few minutes here. BRB..................

[vncj96]

Well I know its happening on idle as it is rough and the truck shakes slightly but I dont have money to invest into that, so off to the shop

[phoebeisis]

I doubt that this will help, but when my intake manifold gaskets were replaced 2 weeks ago the Suburban ended up with a misfire code-P0301 or somrthing like that-it meant #1 wasn't firing.

It turned out to be the "plug" that control the electrical stuff on the fuel injection wasn't seated properly- it had bent one of the male plugs so it wasn't going into the proper female receptor.It was easy enough to do-especially when you are in a hurry. Obviously it isn't the same thing, since that gave a very specific code and cylinder-still it might be a bad connection of something in some not too obvious way.

I would recheck all electrical connections in hopes of getting lucky.
Luck
Charlie

[Dr_Zero]

Oh this reminds me I got a new Harbor Freight sale paper and they have scanners on sale here a link
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=99722

$89 does can and freeze frame internet updatable

or you can get it from Amazon for $79 + shipping
Amazon.com: Autel MaxiScan MS409 OBD-II/EOBD Scanner: Automotive

[TRPLXL2]

You go Dr. Zero, that is all you need and for $89 it will pay for itself after the first time you use it. Plus I am sure that you will use it down the road too, I think they are a good investment but that's just me. The freeze frame is excellent for intermittent problems, and it can also be sent to a lap top for further analysis. The only reason mine cost so much is because I got all of the cables with it, GM/FORD/Chrysler OBD1, GM?FORD?CHRYSLER OBD2, CAN, plus the USB cables. Those cables are like $50 each, so go with the one Dr. Zero showed. It will do the same thing mine does. :great:

[vncj96]

Well its been at the shop since 12 today and it will be there over night, as they are having a hard time figuring it out:neutral:

[vncj96]

Well it has been there since 12 oclock yesterday and no luck yet:grrrrrr:. I really am unsure of what to do, I am gonna have a huge bill for all the computer time to have found nothing.

[vncj96]

I am not sure if its good or bad. My truck has been at the shop since noon yesterday, they have swapped the fuel injectors, switched plugs, tried another distributer, and run a bore scope. They have done a fuel pressure check, cleaned all the injectors and done a compression check. All they know is something is wrong with the number four cylinder. They are running a couple heat checks and the last resort now would be pull the valve cover and then pull the head. They could see the intake valve in the bore scope but not enough room to get to the exhaust side or maybe it was the other way around. They said the compression tests were all around 160.

[Jimmiee]

If the compression tests were indeed all OK what reason would there be to remove the heads? The compression tests would verify that the valves, rings, and head gaskets were OK. I would be asking more questions.

[vncj96]

I missunderstood him, he said they had YET to do the check and that they SHOULD be in the area of 160, low and behold #4 failed, they had air come up the valve after they took the valve cover off