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2015 Chevy Suburban P0305 Misfire

BaileyBunch

By BaileyBunch
in Ask A GM Technician

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BaileyBunch Enthusiast

BaileyBunch

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I have a 2015 Suburban LT. Purchased Cert Pre-Owned. I am at 113K now and just had a P0305 code throw. Took it to the dealership on Monday. It's still there. The said that my spark plugs were bad and have never been replaced, but they replaced them last year at 93K miles. After I told them the date they were able to locate and then walked that back... we are now at $450 in diagnostic fees with no answer. They are doing a pressure test, I think is what they called it and we are waiting for results. I really need help from the GM people out there... ideas of what to expect. The only thing additional I can add is when they got all the spark plugs off they said there was some oil on them. I think they said oil. HELP.

 

edit...pressure test and leak test 

tlaw91 Enthusiast

tlaw91

Posted
Posted

You have a moron tech working on it, it needs an injector. Wtf why are you in the hole $450? My dealer charges $120. What kind of dealership did you bring it to?!!?


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BaileyBunch Enthusiast

BaileyBunch

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2 hours ago, tlaw91 said:

You have a moron tech working on it, it needs an injector. Wtf why are you in the hole $450? My dealer charges $120. What kind of dealership did you bring it to?!!?


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It’s at a GM dealer. They are saying that I may have piston ring damage and that I have 10% more on leak down for cyl 5 and that I could really use a new engine? That’s seems excessive for my light to have just come on?? I took it to the dealer the next day?

BaileyBunch Enthusiast

BaileyBunch

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Also... in the hole 1 1/2 labor for diagnostics only for them to say they need to do a compression test and leak down test. So all the hours of that. 

tlaw91 Enthusiast

tlaw91

Posted
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Oh shoot you’re in my neck of the woods! Cartersville huh? That’s out there a ways.
I’ve never heard of a leak down test failing from a non DOD cylinder before.
I guess anything’s possible but it seriously sounds like an injector. Maybe the injector failed and washed out the cylinder [emoji2369]
I’ve never heard of it.
Your story peaked my interest because of the diag charges! That’s crazy. We don’t charge that at my dealer. Especially when they’ve already dropped the ball on the spark plug guess.


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davester Senior Enthusiast

davester

Posted
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They're already up to wanting to replace the engine...  That really comes across to me as a "how much money can we get out of this person..." style diagnosis.

tlaw91 Enthusiast

tlaw91

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They're already up to wanting to replace the engine...  That really comes across to me as a "how much money can we get out of this person..." style diagnosis.

Right? And they haven’t once mentioned an injector??


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strkpr New Member

strkpr

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Posted

Have you tried "mechanic in a can"? Chemtool injector cleaner fuel additive combined with the Marvel Mystery oil as prescribed on the bottles, my old 2003 Silverado 5.3 with 240,000 miles  had the same code. I ran a tank of the fuel/cleaners and the code never came back. For $15.00 it is worth a try.

BaileyBunch Enthusiast

BaileyBunch

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3 hours ago, tlaw91 said:


Right? And they haven’t once mentioned an injector??


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They haven't mentioned it not one time. 

To the best of my ability, I am going to type in everything that I know, can remember what I have been told.  

 

Saturday night on our way home the check engine light came on. Earlier that day, at a red light we felt a little sputter when it we went to go (After green light). Didn't think much of it. Then the light came on. We parked it, dropped the kids off at school on Monday am and took it to the dealership. It went a little something like this: 

 

It is $60 for half hour for diagnostics. Then they called saying we need you to authorize another hour. I knew going in that the check engine was for the P0305 Misfire because my neighbor has one of the OBD scanners. I think is what it's called. I tried to research some on that Sunday just so I knew what I was getting in to with the dealership. 


They called and said that my spark plugs were bad, that they looked like they had never been changed. Car has 110K not 113K. Anyways, I advised that they had done the spark plugs and wires last year. They said they needed to relook at my RO's. Here we are a day three now. I get a call that AM saying they have never done that for me. Well, I had the RO with me to show that they had. So I asked what I had paid the money for them to do, gave her the $$ and the date of service. Then it was like "ohhhhhhh". At this point, I am seeing red. I asked to speak with Service Manager. 

I get the call the next AM from the service manager. Said that the tech misspoke. That he had only pulled the plug on the 5th cylinder and if it's misfiring of course it will look bad. She checked the parts pull from that previous RO and looked at our plugs and wires and that they are intact new. About 15K miles since that replacement as an FYI. 

Said that when they pulled the other plugs that there was oil on them. They needed to do a Compression Test (this is a three hour labor charge). I approved it because at this point... I am thinking that we are NOT getting the full story. This may be where I made my mistake. But that is how we've ended up at a $450 balance. The tech did a compression test and a leak down test ( I think is what the last one was called). 

 

All I can recall from these additional tests is that something was 10% more on leak down for my 5th cylinder than it should have been? I asked the Service Manager today to send me this stuff via email in writing so I could check with someone else. She said "if he still has it all I can get it notated and in an email to you" well I didn't get any email AND when I called I got VM. I'm back to seeing red my friends. 

This is where we are now with this dealership. Tech said "personally" he'd do new plugs and an oil consumption test. He things that will tell us what the problem he suspects... Piston Ring damage. That it wouldn't be worth it for the Piston Rings to be replaced (this is a $5,696.33 charge) on top of the $450 I owe them. But rather a new engine ("new as in one that has been rebuilt is what I assume) for $6,865.97 plus my $450. 

 

My issue that I told the service manager. 1- your person said it was just plugs. Now... all of this additional shit. 2. How can I trust that this guy knows what he's doing and THREE the biggest of all. I put NO MORE than 15 miles on that car after the check engine light came on. This has NEVER happened before... how do I all of the sudden have all of this horrible major damage done to my car? It was driving fine before and even after the light came on aside from that ONE stutter. 

They have submitted info to GM to see if GM will help cover some of the costs... 

 

In the meantime, one of my Childrens teachers is married to a General Manager of another GM dealer the next town over. I asked her if he would be willing to just listen to me to see if this sounded correct. I talked to him tonight, he said it does seem like a bit of a stretch, that the scenarios could be feasible but a stretch none the less. My car never violently jerked, no smoke, no oil on the ground, no RPMs going up, it didn't run hot. Nothing. He said that his Service Manager sits on some General Motorrs board as far as repairs go, and is on calls to help when other dealerships nationwide have diagnosis issues that they just cannot get to the bottom of and that he would have him reach out to me. Waiting to hear form him, but this Service Manager has been with the dealership a long time and was a certified service tech with them for years before he made Service Manager. This General Manager said, worse case scenario we tow it to my dealership (UM... it is TOTALLY drivable) and he would get me his employee pricing on parts and labor. Anyways... that was a 5:15 tonight and they closed at 6. Hoping I hear back from him on Monday. This guy was kind enough to take my call and was super understanding. I guess because he knows his wife teaches my kid or the fact that he's just a good guy or both. Anyways... my fellow GM smarties here... what do you all say about this? 

davester Senior Enthusiast

davester

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Get your vehicle over to that other dealer ASAP.  I'll bet the current dealer will try jacking up that $450 charge when you go for leaving...

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