Engine Pinging

[coz3z3]

Hello again!

13 Yukon Denali L94, around 195k on replacement motor.
Many of you helped with my recent engine replacement, well the next one is in and I can't figure out what the issue may be. The engine is pinging. Not knocking, not ticking. At first, I thought it was bad gas, and I still haven't completely ruled that out. The gas was well over 1.5 years old. When I got this yukon, the tank was full. I tried to a ton of stabil and cleaners to help at first. It pinged for about 10 minutes before it went away. I was able to drive it for 3 days, about 50 miles, and got the tank to just about the 3/4 mark. Ran like a champ. Then it started pinging again. This time worse. I dropped the tank, siphoned it all out except maybe .5 a gallon. Put me 91 in there with some more cleaner. Now I'm getting a misfire on cylinder 5. I've changed coil, fuel injector, spark plug wire with no avail. The plugs are brand new, my next step is to swap with another cylinder and see if it follows. I did swap with one of the older plugs from the old block and that didn't help. I'm at a loss. I thought it could be the AFM but read that isn't a cylinder that shuts down. But it doesn't sound like a lifter tick. It sounds like predetonation from bad gas. A ping. And I've tried disconnecting the battery to reset the fuel trims as well. Multiple times.

Thank you again!

 

[Trey Hardy]

Hello again!

13 Yukon Denali L94, around 195k on replacement motor.
Many of you helped with my recent engine replacement, well the next one is in and I can't figure out what the issue may be. The engine is pinging. Not knocking, not ticking. At first, I thought it was bad gas, and I still haven't completely ruled that out. The gas was well over 1.5 years old. When I got this yukon, the tank was full. I tried to a ton of stabil and cleaners to help at first. It pinged for about 10 minutes before it went away. I was able to drive it for 3 days, about 50 miles, and got the tank to just about the 3/4 mark. Ran like a champ. Then it started pinging again. This time worse. I dropped the tank, siphoned it all out except maybe .5 a gallon. Put me 91 in there with some more cleaner. Now I'm getting a misfire on cylinder 5. I've changed coil, fuel injector, spark plug wire with no avail. The plugs are brand new, my next step is to swap with another cylinder and see if it follows. I did swap with one of the older plugs from the old block and that didn't help. I'm at a loss. I thought it could be the AFM but read that isn't a cylinder that shuts down. But it doesn't sound like a lifter tick. It sounds like predetonation from bad gas. A ping. And I've tried disconnecting the battery to reset the fuel trims as well. Multiple times.

Thank you again!

On my higher mileage Tahoe 87 would cause it to spark knock it almost sounded like a rod bearing was going bad I put some B12 in the tank and never had the issue again so whenever I run cheap gas I always throw some B12 or a lil marvel mystery oil in with it and it helped eliminate the spark knock

 

[Marky Dissod]

 

[OR VietVet]

Are you seeing a CEL? If so, what was the code(s)?

 

[Foggy]

Add in some "good" octane booster. Lucas, Purple stuff, etc
That would rule out a true predetonation with your 91 fuel.
Also see if you can get 100% gasoline with zero ethanol
The cleaners are full of alcohol type chemicals and could be
adding to the issue

 

[j91z28d1]

when you say plugs were replaced, what kind and where did you get them?

so many bad parts going around

 

[Foggy]

Great point on the spark plugs !!!! Use the ACDelco irridium from a known
source: local parts store, rockauto, summit racing.... NOT: amazon or ebay

 

[coz3z3]

Hello!
Sorry for the late reply, I wasn't getting notifications and decided to check the forum this morning.
I will look at that B12 some more. I have added cleaners, not necessarily octane booster. The cleaners were Lucas, and Amsoil. They both said it should eliminate the predetonation.
Spark Plugs are Delco from O'Reilly. Can't remember the part number off the top of my head, bit they should be what came in it.

CEL has come on. My reader says P0300 is permanent for multiple misfires. Then the only cylinder to post is cylinder 5. P0305. I did get one code for Bank 2 being lean. I thought was weird since that is opposite of cylinder 5. But it only happened once and I cleared it and hasn't come back.

The CEL will come on along with service stabilitrak and all that, then after a couple minutes, they all disappear. Codes stay in computer of course.

Also, the pinging is irratic. Sometimes it is super loud, sometimes it disappears completely for about 2 minutes and then comes back. No matter if it's cold, warm, rpms up, at idle.

Thanks again everyone

 

[coz3z3]

Also, I did swap spark plugs with cylinder 1. No change. I then swapped coil and wire with cylinder 1, no change. I removed the valve cover and all the rockers moved in what seemed like normal fashion. My next step is to get one of those camera scopes and check inside cylinder 5. I'm pretty dumbfounded by this. After that, I'll trace some wires. I've tried unplugging the fuel injector, and coil from cylinder 5 and there has been no change. I'm almost leaning towards a lifter now. But I'm just confused why it goes away sometimes, and it doesn't follow the rpms all the time. It gets faster when the rpms do, but sometimes will slow or go away completely and then not return for 5-10 minutes. Then it comes back slow and not loud.

 

[Trey Hardy]

Hello!
Sorry for the late reply, I wasn't getting notifications and decided to check the forum this morning.
I will look at that B12 some more. I have added cleaners, not necessarily octane booster. The cleaners were Lucas, and Amsoil. They both said it should eliminate the predetonation.
Spark Plugs are Delco from O'Reilly. Can't remember the part number off the top of my head, bit they should be what came in it.

CEL has come on. My reader says P0300 is permanent for multiple misfires. Then the only cylinder to post is cylinder 5. P0305. I did get one code for Bank 2 being lean. I thought was weird since that is opposite of cylinder 5. But it only happened once and I cleared it and hasn't come back.

The CEL will come on along with service stabilitrak and all that, then after a couple minutes, they all disappear. Codes stay in computer of course.

Also, the pinging is irratic. Sometimes it is super loud, sometimes it disappears completely for about 2 minutes and then comes back. No matter if it's cold, warm, rpms up, at idle.

Thanks again everyone

 

[j91z28d1]

might test fuel? maybe you got bad gas and it's running so badly it takes forever to run a tank thru it?

maybe do a compression check? check fuel pressure with a mechanical gauge on the rail, tape it to the windshield and go for a drive? have you looked at your fuel trims? are they showing rich or lean by 25+ plus or minus?

 

[coz3z3]

I got the fuel from Chevron. 91. It was only 6 gallons. I don't know how to test it, it smelled like gas lol. And it definitely smelled better than what was coming out when I dropped the tank.

Compression check will be next. This weekend hopefully. Also, I'm going to borrow a fancy scanner from the shop I used to work at this weekend so I should be able to monitor fuel trims, pressure, coil voltage, etc and hopefully get some kind of idea. It also has the capability to attach one of those cameras so I'll look in cylinder 5 at the valves and what not.

Another note, I got that B12 and put it in last night. Ran it for about an hour. Towards the end of that hour, I was revving it up to about 2500 and it would periodically go away for about 30 seconds. Then come back faintly and then loudly. So can't say if it's actually helping or not yet

 

[j91z28d1]

for checking the fuel, I was mainly thinking water in it. I've heard of that, buddy of mine up in north GA stopped for gas at a small station, bike was running fine. filled up, got a few miles down the road and it ran worse and worse till it died. he ended up towing it home, pulled the fuel tank it it had about a half inch of water in the bottom.

no clue if that's what you have. it just made me think of it. if you could unhook the fuel line or find fuel test port, power the pump and pump some into a clear bottle and see if it separates

 

[coz3z3]

Yeah, I get that. I'm not knocking your idea or anything, I appreciate you giving me your insight. I just don't think it's a possibility with the gas I just purchased. I've been using the same Chevron for 15 years and put it in everything I own. From the pressure washer, up to my Camaro that I track. Now, I do believe that there is still some bad gas in the tank, as I did not get every little bit of it out. There was probably half, to a gallon left in the tank. I would say closer to half a gallon though. Plus whatever was in the fuel pump sump and lines of course. Then, I added 6 gallons of 91 before starting it up. Then added that B12 now. I believe something else is going on. Since cylinder 5 is the only one that keeps coming up as a misfire. I think if it truly was bad gas, I would just be getting random misfires from everywhere or just the P0300 code. I was unable to get the scanner from my old shop this weekend. My buddy said that he will definitely get it to me for next weekend though. So for now, it will be on the back burner, but I will continue to fire it up and let it run to see if there is still a chance the bad gas hasn't been burned out yet. Thank you again for replying, I appreciate your insight as well as everyone else's!

 

[j91z28d1]

yeah no worries, I was just clarifying the guess.

since you can't get a ahold of a scanner this weakened, can you pull the plug on that cyl and see what it looks like. might give a clue as to why it's missing in that one. I've even seen a loose plug cause a misfire.

 

[coz3z3]

Didn't pull the plug this weekend, but did last weekend and it looked fine. Not wet, not black or anything. Swapped it with cylinder 1, nothing happened. Swapped it with 2 other spark plugs from the old motor, no change. I'm leaning towards a possible lifter or I pinched a wire somewhere somehow.

 

[coz3z3]

Just to give an update on this in case that someone stumbles across a similar issue. I was able to pull the spark plug on cylinder 5 and stick a camera in there attached to the scan tool. Found what looks like a hole in the piston. It was a used motor, so I contacted the place that I received it and they sent out another one on warranty. I was able to get it in this past weekend, and it sounds so much better. Even when the other motor was running decent, this one sounds much more healthy. I drained the oil in the faulty motor thinking that I would use it in the warrantied motor since it had such little miles on it. It came out all murky looking, like exhaust gases were getting mixed in with it. So that would explain it lol. Thanks for everyone's suggestions! Hopefully this is the last issue on the motors! lol

 

[jdwood1111]

Just to give an update on this in case that someone stumbles across a similar issue. I was able to pull the spark plug on cylinder 5 and stick a camera in there attached to the scan tool. Found what looks like a hole in the piston. It was a used motor, so I contacted the place that I received it and they sent out another one on warranty. I was able to get it in this past weekend, and it sounds so much better. Even when the other motor was running decent, this one sounds much more healthy. I drained the oil in the faulty motor thinking that I would use it in the warrantied motor since it had such little miles on it. It came out all murky looking, like exhaust gases were getting mixed in with it. So that would explain it lol. Thanks for everyone's suggestions! Hopefully this is the last issue on the motors! lol

Where did you get the motor that they gave a new one via the warranty? Seems like many places fight tooth and nail on warranties and it’s good to know some good ones exist! Glad it worked out for you!

 

[coz3z3]

Through Ebay, Butler Auto Recycling to be specific. https://www.ebay.com/str/butlerautorecyclinginc

They were great, cost was a little on the high side, no core charge though. 90 day warranty. I contacted them as it was still in warranty, I told what steps I have done and told them that the piston looks to have a hole in it. They said typically they try to do repairs, but with a hole in the piston, probably not the best option. They asked me to take a picture of the "heat tabs" they put on the motor. I pulled the motor as I could not find it, sent them a ton of pictures saying there was not any on the motor. They contacted me and said, "sounds good, we will have another motor shipped out to you". Came within a week across the country. As of today, I am not sure what they want to do with the original motor. They told me they will worry about that after I get this one in and all seems well. I haven't heard anything from them about sending it back yet. Although, I wouldn't mind having an extra 6.2l block lying around lol

 

[OR VietVet]

Keep it.