P0300 code after replacing parts

[MalcDogg]

Hello everyone
Let’s just start 2008 Chevy Tahoe
Got a misfire code P0307 found out it was the lifter so I replaced all the lifters, cam, spark plugs, head gaskets, intake gaskets, timing chain and sprockets, also replaced the cats and 02 sensors

Now it’s throwing P0300 codes and engine idles rough and sometimes stall

Anyone got any ideas or solutions

 

[petethepug]

Whoa, you got a lot done. Just keeping it simple and guessing it didn’t have the same code before. If you pulled the spark plug leads you may have damaged one or more of them in the process. Buy a new cheapie set and see if that cleans up the idle.

Did you replace the lifter buckets with OEM?

 

[MalcDogg]

I replaced the lifter guides aswell I also installed new spark plugs and still getting a misfire

I’m thinking it could be the heads not torqued correctly because of some cheap bolts for eBay that didn’t go in easy I’m thinking that could be the problem spark plugs is getting wet

 

[iamdub]

 

[OR VietVet]

@petethepug was asking about plug wires, when he said "leads". I would also be worried about a vacuum leak. Are you sure all air tube connections are tight between the air filter housing, MAF and throttle body? Double check the MAF connector and make sure a wire is not pushed out of connector. Damaged the cam and or crank sensors? You did a lot of work and now have to recheck the work. If you torqued down the head bolts correctly, they should be ok but go ahead and recheck.

 

[OR VietVet]

I replaced the lifter guides aswell I also installed new spark plugs and still getting a misfire

I’m thinking it could be the heads not torqued correctly because of some cheap bolts for eBay that didn’t go in easy I’m thinking that could be the problem spark plugs is getting wet

Wet plugs, if it is fuel, typically means a spark problem. What color is the spark? Blue=good, orange=bad.

 

[MalcDogg]

Wet plugs, if it is fuel, typically means a spark problem. What color is the spark? Blue=good, orange=bad.

the spark plugs is black not all of just about 3 or 4 them some oil on them from inside the cylinders I’ll be putting everything back together today hopefully no misfiring all vacuum hoses and lines is good no leaks there

 

[Dustin Jackson]

@MalcDogg Checking your compression might be a good place to start if you suspect the head isn’t installed properly

 

[MalcDogg]

@MalcDogg Checking your compression might be a good place to start if you suspect the head isn’t installed properly

I’m gonna do a compression test today I got everything out back together and still get a random misfire I’m also getting a U 0101 code

But I did forget to mention I had some cheap cats and replaced them they was hollow after taking them off I’m thinking the muffler could be causing this aswell being that it’s clogged with the old cats stuff ‍
What u think about that?

 

[Dustin Jackson]

@MalcDogg I think if it was the cats you would have an O2 sensor or cat efficiency code

 

[MalcDogg]

I scan it and it keeps saying P0300 check cats O2 sensors

 

[Dustin Jackson]

@MalcDogg Might be worth installing some of your old parts but a p0300 code is for a random misfire, it looks like your emission monitor for the o2 sensors isn't set yet so that could indicate a problem with the cats or O2 sensors.

I would start with a compression test and then maybe install your old O2 sensors?

 

[MalcDogg]

@MalcDogg Might be worth installing some of your old parts but a p0300 code is for a random misfire, it looks like your emission monitor for the o2 sensors isn't set yet so that could indicate a problem with the cats or O2 sensors.

I would start with a compression test and then maybe install your old O2 sensors?

I think I may have figured this out but because of rain and no garage I’ll have to wait

I noticed 2 of the valves is not flushed with heads and notice some marks on the top of the pistons it’s dumping oil in the cylinders causing the misfire and blue smoke on start up so I think I’m gonna remove the heads once more and address them valves look like I’ll be replacing all the valve and the components

 

[Dustin Jackson]

@MalcDogg Sounds like could be using too long push rods. Sounds like a strange situation

 

[MalcDogg]

Well here’s an update

Went back into the engine replaced the valves and am the seals everything seems to be working fine a get a misfire then it goes away a lot of smoke coming from the tail pipe when I sit and then take off seems like it’s burning away the carbon build up from me cleaning the heads so now I think everything is good so far

 

[OR VietVet]

Well here’s an update

Went back into the engine replaced the valves and am the seals everything seems to be working fine a get a misfire then it goes away a lot of smoke coming from the tail pipe when I sit and then take off seems like it’s burning away the carbon build up from me cleaning the heads so now I think everything is good so far

WHAT does this mean? It is jibberish.....When you get old, like me, I need punctuation and sentences that end and start. Sheesh...

 

[Dustin Jackson]

@MalcDogg something doesn’t sound right man you shouldn’t be having misfires and smog coming out the tailpipe. If it quit happening and isn’t happening anymore that’s fine but if you continue to have that problem that’s not right. I had my heads redone last year with a wire wheel and never had a lick of what you’re describing

 

[swathdiver]

When you pulled the heads the 2nd time, did you use all new bolts and head gaskets? You mentioned using ebay parts, are they genuine GM?

Are you doing an AFM delete or keeping it original? It is SOP to replace the VLOM as it is this component that fails and ruins the lifters most often.

 

[Geotrash]

Well here’s an update

Went back into the engine replaced the valves and am the seals everything seems to be working fine a get a misfire then it goes away a lot of smoke coming from the tail pipe when I sit and then take off seems like it’s burning away the carbon build up from me cleaning the heads so now I think everything is good so far

What color is the smoke? Blue = oil. White = coolant.

 

[MalcDogg]

What color is the smoke? Blue = oil. White = coolant.

Blue smells like oil