Chasing a rough idle?

[2009TahoeLT]

Anything else I can do or check in the meantime?

 

[2009TahoeLT]

Found another evap leak at the charcoal canister. Fixed that. No changes. O2 sensor readings look ok. Still adding fuel and misfiring. All cylinders misfire at 1100 rpm except for cylinder 6

 

[swathdiver]

Ok so my 2009 Tahoe 5.3 has been running a bit rough/choppy.

...I’ve replaced all plugs, wires. Replaced intake manifold gasket. Replaced purge valve. Fuel pump was replaced. Cleaned maf.

What plugs and wires did you use?

Did you confirm the gap on each of the plugs?

Are you CERTAIN that the injector connectors are on the correct injector? Did you check it three times? BTDT.

Same for the plug wires.

Is your brake booster hose connected to the back of the intake? Are the PCV hoses that go into the intake sealed tight?

Have you checked the intake gaskets for leaks since you installed the new ones?

If you've done all of these things, pull the plugs and inspect them. What do they look like?

Are all cylinders misfiring on the scan tool?

 

[rdezs]

250,000 mi on it.... I'd want to take a look at that timing chain. Might have jumped a tooth. Then might as well replace it and the oil pump while you're in there.

Before doing that I'd want to do a compression check and a leak down test.

Keep in mind a lot of times the camshaft position sensor does not throw a code. If it was off a tooth, the ECM would be all over the place trying to make it run and throwing codes for misfires and whatever.

 

[2009TahoeLT]

What plugs and wires did you use?

Did you confirm the gap on each of the plugs?

Are you CERTAIN that the injector connectors are on the correct injector? Did you check it three times? BTDT.

Same for the plug wires.

Is your brake booster hose connected to the back of the intake? Are the PCV hoses that go into the intake sealed tight?

Have you checked the intake gaskets for leaks since you installed the new ones?

If you've done all of these things, pull the plugs and inspect them. What do they look like?

Are all cylinders misfiring on the scan tool?

Copper ac delco plugs, ac delco wires. Gap was confirmed before install. I’m not 100 percent sure on injector connectors tbh but could be switched somewhere. I don’t believe so though. Plug wires go where needed. Booster hose is connected. No leak with new intake gasket. Also all new intake bolts. Does have a decent exhaust manifold leak but the manifold bolts are rusted very bad. I just pulled the plugs earlier. I’ll attach a picture. All cylinders besides cylinder 6 are misfiring only at 1100-1600 rpm. And not enough to throw a code but can hear the popping from the exhaust exit

 

[2009TahoeLT]

250,000 mi on it.... I'd want to take a look at that timing chain. Might have jumped a tooth. Then might as well replace it and the oil pump while you're in there.

Before doing that I'd want to do a compression check and a leak down test.

Keep in mind a lot of times the camshaft position sensor does not throw a code. If it was off a tooth, the ECM would be all over the place trying to make it run and throwing codes for misfires and whatever.

Yeah it doesn’t throw codes but it’s adding fuel and misfiring on every cylinder but cylinder 6, but only at 1100-1600rpm. I may try and see if my buddy has a compression tester to take a look.

 

[Doubeleive]

if you cant get the 02 out I would maybe try and just unbolt the y-pipe and either get it that way or see if it the misfire is still there wide open with no cats on
maybe even just unbolt the 3rd cat. mine was clogged so we gutted it, it's not monitored so sensor don't care

 

[2009TahoeLT]

if you cant get the 02 out I would maybe try and just unbolt the y-pipe and either get it that way or see if it the misfire is still there wide open with no cats on
maybe even just unbolt the 3rd cat. mine was clogged so we gutted it, it's not monitored so sensor don't care

Y pipe is completely rusted. Bolts will snap without a doubt

 

[Fless]

Did I miss the reason for running copper plugs instead of platinum or iridium?

 

[2009TahoeLT]

Did I miss the reason for running copper plugs instead of platinum or iridium?

My buddy recommended copper as they are better but just have to switch them out more frequently

 

[2009TahoeLT]

Also plugs are white which usually means it’s running lean correct? But then trims show its adding fuel. So I’m lost haha

 

[rdezs]

Plugs are white.... All of them? Well that would require combustion, which would require compression. I doubt you forgot to put on the intake manifold gasket? LOL. If you're positive there's no vacuum leaks.... Then you should take a close look at your fuel system including the O2 sensors. Plugged catalytic converters or muffler would foul your plugs black. If the fuel numbers are correct and it's running that lean, it's a very large vacuum leak. Try unplugging the large vacuum line to the power brake booster, and plug the port on the manifold. If that fixes it, you have a ruptured brake booster diaphragm.

 

[2009TahoeLT]

Plugs are white.... All of them? Well that would require combustion, which would require compression. I doubt you forgot to put on the intake manifold gasket? LOL. If you're positive there's no vacuum leaks.... Then you should take a close look at your fuel system including the O2 sensors. Plugged catalytic converters or muffler would foul your plugs black. If the fuel numbers are correct and it's running that lean, it's a very large vacuum leak. Try unplugging the large vacuum line to the power brake booster, and plug the port on the manifold. If that fixes it, you have a ruptured brake booster diaphragm.

Yeah I had a huge vacuum leak and found the line to the charcoal canister was loose. Pushed it on tighter and smoke tested the system again. No visible smoke leaks and tank pressure was holding steady with vent valve closed. Intake manifold gasket is definitely in there. I installed the newer updated metal one.

 

[swathdiver]

Haven't used copper plugs in decades.

 

[donjetman]

I use copper plugs in my race engines
and
in my 233k mile 07 Toyota 4.0L since new, and change them every 50k miles. Cost as little as $4/plug

 

[swathdiver]

I use copper plugs in my race engines
and
in my 233k mile 07 Toyota 4.0L since new, and change them every 50k miles. Cost as little as $4/plug

I seem to remember Richard Holdener dyno testing different plugs and gaps and nothing was more than 5 horsepower off the factory Iridiums.

What is to like about the copper plugs over the new stuff?

 

[donjetman]

What is to like about the copper plugs over the new stuff?

Copper=Toyota FJ Cruiser oem in 2007, $4/plug, they work great.
Its never thrown a code, burned or leaked any oil, still has all original sensors, coils, etc, etc.
It's almost a NO mx vehicle

Copper is what everybody I know runs in their race engine(s) for the last 40 yrs. Again they work.

I don't run copper in my other vehicles

 

[2009TahoeLT]

So small update. Here are the compression numbers. Now throwing codes for cylinder 5 misfire and also a p0300, bank 1 lean, oil pressure and a large evap leak. Motor bogs down bad when coming to a slow stop. When it misfires bad the engine light flashes and traction control turns off and stabilitrak turns off. The plug in the picture is cylinder 6 that has the highest compression. I’ve tried swapping plug, coil and wire with 5 and 3. It did not follow to 3. Just gapped all the plugs again. They were at .45. They are now at .40. Also cleaned out all the injectors. I did recently unplug the front o2 sensors and drove it a little bit. Seemed to have some of its pep back but was still misfiring.

 

[2009TahoeLT]

View attachment 453525View attachment 453526
So small update. Here are the compression numbers. Now throwing codes for cylinder 5 misfire and also a p0300, bank 1 lean, oil pressure and a large evap leak. Motor bogs down bad when coming to a slow stop. When it misfires bad the engine light flashes and traction control turns off and stabilitrak turns off. The plug in the picture is cylinder 6 that has the highest compression. I’ve tried swapping plug, coil and wire with 5 and 3. It did not follow to 3. Just gapped all the plugs again. They were at .45. They are now at .40. Also cleaned out all the injectors. I did recently unplug the front o2 sensors and drove it a little bit. Seemed to have some of its pep back but was still misfiring.

Ok so also found the fscm fuse had a weird like burned grease film on it. Looks like previous owner put some sort of grease in it and it didn’t like it lol. Replaced the fuse and started her up. Check engine light immediately went away. Unfortunately still idles rough but is idling at about 580-620 which is better than the 480-520 before. Also still misfiring really bad on all cylinders at about 1100-1800 rpm

 

[donjetman]

@2009TahoeLT
I had misfiring/rough idling caused by counterfeit spark plugs.
Here's the thread I did : https://www.tahoeyukonforum.com/thr...iring-at-idle-counterfeit-spark-plugs.146952/