Misfire triggers armageddon!

[Fudpucker]

First, the car is a 2007 Yukon, well kept. Oil changed every 3-5000 miles. This car has been my ride for a long time and gone cross country at least 6 times. Ran like a baller, ALL the time, then one day I feel it missing, and of course that misfire sets off all kinds of other alarms (Stabilitrack Engine light etc...) It starts shifting like a 13 year old learning how to drive stick shift. I was like wtf??? I took it in for an oil change because the stick did say it was a quart or so low, and eventually, everything corrected itself. Car ran fine, all the lights went out on their own and because all the lights were off, it shifted fine. Another 1000 or 2000 miles later, exact same thing. The misfire obviously triggers everything else. I did an early oil change......wouldn't correct itself. Brought it in to a friend's shop and they told me it was a worn cam-lobe on the #7 cylinder. I was like "huh?" If that was the case, this wouldn't have corrected itself the last time. I drove it home, low and behold, 4 days later.....all is fine. Last place was telling me I needed a new engine.

Now, weeks after being just fine, it's doing it again and I'm leaving for a 2000 mile road trip in 5 days. I need to get this taken care of once and for all.

What I've seen so far is intake-leaks being the main culprit. Last place said they checked all the coil packs and they were fine, or at least the replaced the number7 and it still misfired.

Is there anything anyone's put their finger on yet? I love this vehicle! Obviously, with 250,000 miles on it, I can see things going wrong but being that this has happened soo many times before, and resolved itself, it tells me it's something that can be fixed.

Any ideas are appreciated!

 

[wjburken]

First, the car is a 2007 Yukon, well kept. Oil changed every 3-5000 miles. This car has been my ride for a long time and gone cross country at least 6 times. Ran like a baller, ALL the time, then one day I feel it missing, and of course that misfire sets off all kinds of other alarms (Stabilitrack Engine light etc...) It starts shifting like a 13 year old learning how to drive stick shift. I was like wtf??? I took it in for an oil change because the stick did say it was a quart or so low, and eventually, everything corrected itself. Car ran fine, all the lights went out on their own and because all the lights were off, it shifted fine. Another 1000 or 2000 miles later, exact same thing. The misfire obviously triggers everything else. I did an early oil change......wouldn't correct itself. Brought it in to a friend's shop and they told me it was a worn cam-lobe on the #7 cylinder. I was like "huh?" If that was the case, this wouldn't have corrected itself the last time. I drove it home, low and behold, 4 days later.....all is fine. Last place was telling me I needed a new engine.

Now, weeks after being just fine, it's doing it again and I'm leaving for a 2000 mile road trip in 5 days. I need to get this taken care of once and for all.

What I've seen so far is intake-leaks being the main culprit. Last place said they checked all the coil packs and they were fine, or at least the replaced the number7 and it still misfired.

Is there anything anyone's put their finger on yet? I love this vehicle! Obviously, with 250,000 miles on it, I can see things going wrong but being that this has happened soo many times before, and resolved itself, it tells me it's something that can be fixed.

Any ideas are appreciated!

Do you have the 5.3 or the 6.2?

What do your plugs look like? How old are they? How old are the wires?

Are you hearing any lifter noise or tapping when your motor is running?

What are the codes you are getting?

 

[Doubeleive]

lol, a oil change is not going to correct a misfire, they are not related at all (at least not in general terms as far as changing the oil, oil could be fouling a plug but simply changing the oil alone would not correct the problem), what codes are you getting?

 

[BG1988]

First, the car is a 2007 Yukon, well kept. Oil changed every 3-5000 miles. This car has been my ride for a long time and gone cross country at least 6 times. Ran like a baller, ALL the time, then one day I feel it missing, and of course that misfire sets off all kinds of other alarms (Stabilitrack Engine light etc...) It starts shifting like a 13 year old learning how to drive stick shift. I was like wtf??? I took it in for an oil change because the stick did say it was a quart or so low, and eventually, everything corrected itself. Car ran fine, all the lights went out on their own and because all the lights were off, it shifted fine. Another 1000 or 2000 miles later, exact same thing. The misfire obviously triggers everything else. I did an early oil change......wouldn't correct itself. Brought it in to a friend's shop and they told me it was a worn cam-lobe on the #7 cylinder. I was like "huh?" If that was the case, this wouldn't have corrected itself the last time. I drove it home, low and behold, 4 days later.....all is fine. Last place was telling me I needed a new engine.

Now, weeks after being just fine, it's doing it again and I'm leaving for a 2000 mile road trip in 5 days. I need to get this taken care of once and for all.

What I've seen so far is intake-leaks being the main culprit. Last place said they checked all the coil packs and they were fine, or at least the replaced the number7 and it still misfired.

Is there anything anyone's put their finger on yet? I love this vehicle! Obviously, with 250,000 miles on it, I can see things going wrong but being that this has happened soo many times before, and resolved itself, it tells me it's something that can be fixed.

Any ideas are appreciated!

it's common for ground wires to open at this age
even if you got a california car they can still get quite crusty..

 

[avalonandl]

Your issue sounds like the classic case of poor voltage: causes can be battery going bad, bad ground connection, etc.

Pull your plugs and see what they look like.

 

[Fudpucker]

Do you have the 5.3 or the 6.2?

What do your plugs look like? How old are they? How old are the wires?

Are you hearing any lifter noise or tapping when your motor is running?

What are the codes you are getting?

5.3. Supposedly plugs were ok. Wires, they swapped some wires and were still getting the #7 misfire. Code is P0307

 

[swathdiver]

5.3. Supposedly plugs were ok. Wires, they swapped some wires and were still getting the #7 misfire. Code is P0307

You're probably in need of a new lifter on #7 and a VLOM. Sometimes its a broken valve spring but symptoms would be different.

 

[RET423]

Add my vote to an electrical issue, bad ground or poor connection in a harness; possibly a loose plate in the battery that causes your "Armageddon" when it drifts over enough to touch another plate.

 

[OR VietVet]

Ditto on the wiring/grounds problems. Many many stories here about such things.

 

[shegarty]

My 04 Burb had similar issues when the main engine block ground went bad. It would only show up when the engine was hot. There was also no warning and to top it off we were on a road trip when it first showed up. When it happened it would throw the truck into "reduced power" mode which was unfortunate because I was pulling the camper. I was able to get it home by clearing the misfire codes with a simple OBDII scanner but when it finally cooled completely at home that was it - total no start and crazy electrical stuff everywhere (door locks, lights, throttle body ...). Did I mention that this was after having one of the main brake lines from the distribution block split? |Needless to say we don't have the greatest track record with road trips

To me a worn cam lobe would be more consistent and would cause a regular misfire and I would hold off on major engine work until you have eliminated ALL potential electrical issues. There are lots of resources here detailing the known culprits. You can check and repair almost all of them yourself without any mechanical knowledge and some basic hand tools.