2010 Tahoe/Cylinder 1 trouble

[Txfiredude]

Hello all, I am at my wits end trying to figure this out. Hopefully one of you has had a similar problem that you have solved. Engine on my wifes 2010 Chevy Tahoe 5.3 is throwing a p0301 code. Replaced spark plug, spark plug wires, coil pack, and injector. It has 250k ish miles and each cylinder is showing roughly 100 psi of compression including the trouble cylinder. Fuel pressure is reading 60 psi. Confirmed that the spark plug is firing by putting an old one and new one on the spark plug wire while the car is running and observing good spark. Pulled the lifter cover and the lifter isn't jammed or bad. It lifts just like all the other cylinders. I know its cylinder 1 due to disconnecting the spark plug wire while its running and it does not change the rough idle. Pulling other wires obviously makes the idle worse. Only things I can think of left are the crankshaft positioning sensor and the PCM. It also throws a stabilitrack and traction control error with the p0301 code so I'm not sure if that's the problem. Any input appreciated, thanks!

 

[OR VietVet]

Welcome to the forum from Oregon.

100 psi is not good compression. Did you take all the plugs out and then do the compression? How did you do the compression check? What color is the spark? You want blue, not orange or yellow. You have a code of P0301 but does it idle rough? Can you feel a miss when accelerate?

 

[Txfiredude]

Welcome to the forum from Oregon.

100 psi is not good compression. Did you take all the plugs out and then do the compression? How did you do the compression check? What color is the spark? You want blue, not orange or yellow. You have a code of P0301 but does it idle rough? Can you feel a miss when accelerate?

Yea I looked it up and 100 is low but its also an older high mileage engine. We have a compression gauge that screws into the spark plug port. The spark was blue, tested several different cables and plugs but it was always blue. Yea it idles rough, kinda smooths out at higher rpms and goes back to rough idle. No matter the speed or RPMs you can still feel it.

 

[solli5pack]

Did you check compression on the other cyl's? If believe if one if 10% less than the others than that's bad...I would go with a leakdown test after that. Sounds like you covered the spark part but you could swap injectors with another cyl and see if that misfire follows. After that you're gonna need a scanner that shows live data. No lifter noise?

 

[OR VietVet]

Yea I looked it up and 100 is low but its also an older high mileage engine. We have a compression gauge that screws into the spark plug port. The spark was blue, tested several different cables and plugs but it was always blue. Yea it idles rough, kinda smooths out at higher rpms and goes back to rough idle. No matter the speed or RPMs you can still feel it.

You did not answer my question. Did you remove all plugs and then do a complete compression test? Write down all the different compressions.

 

[j91z28d1]

noid light to check if there's a wiring issue with the injector?

 

[Txfiredude]

You did not answer my question. Did you remove all plugs and then do a complete compression test? Write down all the different compressions.

Apologies, We compression tested all the cylinders on the driver side of the engine and they all read about the same. 1. 100 3. 105 5. 103 7. 105

 

[Txfiredude]

I have not done that, I smelled gas on the injector and moved on. I should do an

noid light to check if there's a wiring issue with the injector?

actual test on it though.

 

[Txfiredude]

They all read the same give or take 5 PSI. I also put a new injector on that cylinder to be safe and it didn't fix it.

 

[Txfiredude]

Did you check compression on the other cyl's? If believe if one if 10% less than the others than that's bad...I would go with a leakdown test after that. Sounds like you covered the spark part but you could swap injectors with another cyl and see if that misfire follows. After that you're gonna need a scanner that shows live data. No lifter noise?

They all read the same give or take 5 PSI. I also put a new injector on that cylinder to be safe and it didn't fix it.

 

[j91z28d1]

having 4 plus still in can slow down how faster the starter and spin over. and since you're doing a cranking compression test. a small amount of speed can cause a big difference in psi.

that's why he asked.

but yes, just replacing the injector doesn't mean its getting the signal form the ecm to open. also where did you get the injector? hang on to the old one, as it's probably best to put in back in after you solve the miss. these cheap Amazon/ebay no name injectors have a totally different opening time compared to oem. very expensive aftermarket injectors come with that data which will then be programed into the ecm to compensate using something like hptuners software. short if that, it'***** or miss.

 

[OR VietVet]

@j91z28d1, finally said what I was asking about. I guess I should have been more clear. But I would have thought my question was easy. I give up at this point.

 

[Txfiredude]

The injector was from Orileys, whatever they had for the replacement. I might have to revisit the PSI and see if that's the reason since I addressed everything else as best I could.

 

[Txfiredude]

@j91z28d1, finally said what I was asking about. I guess I should have been more clear. But I would have thought my question was easy. I give up at this point.

I put each cylinder reading on the other post

 

[j91z28d1]

I mean you can redo the the test and see if it all comes up. that back plug on the pass side is hard for most people.


if you have the old injector handy, quick test would be unplug the one on the engine, plug in the old one and hold it in your hand. start the truck. you should be able to feel it opening and closing.. there's 12v postive to one side of the injector plug and the other is ground from the ecm. it turns the ground on and off quickly to open and close it.

just something to rule out.

 

[Txfiredude]

I mean you can redo the the test and see if it all comes up. that back plug on the pass side is hard for most people.


if you have the old injector handy, quick test would be unplug the one on the engine, plug in the old one and hold it in your hand. start the truck. you should be able to feel it opening and closing.. there's 12v postive to one side of the injector plug and the other is ground from the ecm. it turns the ground on and off quickly to open and close it.

just something to rule out.

ok i will try that, thank you