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Discussion Starter · #1 ·
I have a 2004 silverado 2500 6.0 with a 4l60e trans. When I am doing 80 on the freeway, it runs at 3000 rpm. Does this sound right? The shop that had just rebuilt my trans had said that my p0300 (random misfire) code is keeping my torque converter from locking up. Does this sound right?
 

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No and yes. It’s a 80e, and Is the check engine flashing at you?

Trans doesn’t care about missfires, but the engine will limp out if you’re constantly missing, and throw so much torque reduction you can’t lock the conveter up. However it would run so bad you wouldnt be able to get past 50mph to throw them tables.
 

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Discussion Starter · #3 ·
Yes the engine light flashes, but the drivability doesn’t change. It doesn’t seem like it goes into overdrive, but it does go through all 4 gears. The transmission place said it does go into overdrive but the converter doesn’t lock up. Personally, I think they are giving me a load of shit, but who knows. The rpm is always roughly 3000 at 80. That is what didn’t seem right to me. I was looking at charts, and it says that the speed, gear, and rpm are the same as I’m getting while driving. I don’t really think there is anything wrong now, would you agree?
 

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Yes the engine light flashes, but the drivability doesn’t change. It doesn’t seem like it goes into overdrive, but it does go through all 4 gears. The transmission place said it does go into overdrive but the converter doesn’t lock up. Personally, I think they are giving me a load of shit, but who knows. The rpm is always roughly 3000 at 80. That is what didn’t seem right to me. I was looking at charts, and it says that the speed, gear, and rpm are the same as I’m getting while driving. I don’t really think there is anything wrong now, would you agree?
Flashing check engine is a dead miss, and it will prevent lock up and rob power.

Regardless of what’s up with the trans, you have a serious issue on the motor that needs to be fixed before you even worry about hitting over drive.
 

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Discussion Starter · #5 ·
Ok. I’ve done damn near everything to solve the misfire problem besides a valve job. I have found out that cylinders 1 and 6 are missing. But the truck drives fine. The light only flashes when I am above 2000 rpm. The motor has almost 300k miles on it. I could do a valve job but I was planning on putting a rebuilt motor in it, so there would be really no point on doing a valve job.
 

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Discussion Starter · #6 ·
I have also tried fuel additives to try and clean the valves. I have used 2 bottles already and it hasn’t helped.
 

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So what did you even try?
 

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The motor is running on 6 cylinders. The motor isn’t stupid and will prevent lock up of the trans so you don’t blow it up.

Why would you default to valves?
 

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Discussion Starter · #9 ·
I had done new plug wires, coil packs, spark plugs, a crank relearn, and fuel injectors. After none of that worked I had taken it into a shop and asked them if they could just figure out what is wrong. They said that it is most likely the valves sticking. It just confuses me because the truck runs like all 8 cylinders are firing. There is no power loss that I can feel and everything sounds fine.
 

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I had done new plug wires, coil packs, spark plugs, a crank relearn, and fuel injectors. After none of that worked I had taken it into a shop and asked them if they could just figure out what is wrong. They said that it is most likely the valves sticking. It just confuses me because the truck runs like all 8 cylinders are firing. There is no power loss that I can feel and everything sounds fine.
So you pissed away money with no clue what you where doing?
 

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Did anyone think about 02s or the terrible exhaust you have on it?
 

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Discussion Starter · #13 ·
The shop I took it into said that compression at idle was good but one there was acceleration, it was not good. That’s also why he thought it was a valve problem.
 

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The shop I took it into said that compression at idle was good but one there was acceleration, it was not good. That’s also why he thought it was a valve problem.
There checking compression at with the motor running?
 

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Once again, someone is just slapping parts at it until it’s fixed. Bring it to a shop that can actually data log it, or has the experience in that motor.

I personally have a wall of over 50 LS heads from part outs and swaps. Never have I seen a “sticking” valve on an LS. Also never seen a coil pack besides #8 go bad, cause the heater core leaks on it. Sounds like there running you around.
 

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Discussion Starter · #16 ·
Yeah that’s kind of what I was thinking. What other things do you think could be wrong that I could look into. I know it is kind of a mess. I’m kind of tired of replacing parts and being told it is one thing and it not being that. I mean if you could give me any suggestions on what I could look at, that would be great. I did notice that my code reader was flashing the I/M readiness lights for 02s, CAT, and there was one more but I would have to plug my reader in because I couldn’t remember. So do you think it could be something with the exhaust? You did say something about it having a shitty exhaust in an earlier reply.
 

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You already did the basics. Then again depending the brand of some of them parts you may have worked backwards. It’s really hard to say without some actual data.

Check the fuel rails and see if you have two fuel lines coming in, or a single. If it’s two then you a return style, check fuel pressure. Pump and regulator go out a lot on them, plus you have an in-line fuel filter. The single line, returnless style doesn’t have many problems, and no filter.

Besides that start unplugging things while it’s running. Mainly MAF and injectors. Once you unplug one and notice no difference in motor speed/idle you found the problem.
 

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Discussion Starter · #18 ·
Ok thank you, I will look into that. I am wondering about the MAF. The guy I bought the truck from put a cheap ass cold air intake that is a pain to take off and on. So I am wondering if that could possibly be a problem. Thanks for the help!
 

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Discussion Starter · #19 ·
So if I need to go on a 6 hour drive doing about 75 the whole way up. Will that cause transmission damage?
 

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So if I need to go on a 6 hour drive doing about 75 the whole way up. Will that cause transmission damage?
I’d be more concerned with the motor than the trans.

As long as it’s no staying in a loop of locking and unlocking you should be fine, just burn a little more gas. Just keep an eye on the trans temps
 
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