08 Tahoe 6.0L LFA - Bent Rod??? Is That Even Likely?

[tiktok4321]

Cross posted in Hybrid forum, but since this is a mechanical issue rather than a hybrid issue, I am posting here, too.

Two weekends ago, my 08 Tahoe Hybrid had to be towed to the shop with a Cylinder 6 misfire. The mechanic is giving me weird stories, and I don't know whether to trust him or not.

He initially claimed that it was only getting 75 PSI in that cylinder, and that he scoped it and the cylinder wasn't making TDC - implying that it had a bent connecting rod. I've heard of that happening, but really - what is the chance of running smooth for hours, then suddenly getting vapor lock, and bending the rod??

Fast forward to this past weekend. After Irma had his shop closed for 8 days, I went back and talked to him. When I asked the vapor lock question to the mechanic, he never even hinted that it was a rod issue.

Same guy recently did a full head/lifter job just 4 months ago on that same side of the engine. Could an error in putting it back together manifest itself after that period of time?

This Hoe is getting to be a real headache!! Every time there is an engine issue, they want to replace the whole thing.

Any help, comments, etc would be appreciated.

 

[iamdub]

Any chance he'll let you view the scope? I don't know about vapor lock, but HYDROlock from an injector sticking open and dumping fuel into the cylinder will bend a rod. This would be plain ****** luck and neither of you at fault.

Now, if the problem actually is low compression and not from a bent rod, then it could be from mechanical failure resulting from something he worked on previously such as a failure in the valve train or head gasket seal.

 

[tiktok4321]

I will have to see what he's got to say. Was expecting a call yesterday.

 

[tiktok4321]

Three weeks in the shop and he still has it. I'll give him one week for the hurricane, but still...

Last word was that it may not be anything more than a bad injector. He wouldn't check that before tearing apart the head???

 

[iamdub]

Dude... Go get your Tahoe YESTERDAY.

He said he ran a compression test and saw 75psi on cylinder #6 and that he scoped it and saw that the piston wasn't making TDC. NOW, it may not be anything more than a bad injector?! That straight up disregards anything he told you before. AND he's already started tearing into it without an accurate diagnosis? Did you even permit him to proceed? You're getting yanked around. Sounds like one of those shady places that if you go to get it, they won't give you the keys until you pay some ridiculous diagnostics and labor charges.

 

[tiktok4321]

He's done me right before. This is just strange for him to be acting this way. He DID say there was a "little" issue with the head and now it's getting compression, but he still gets a misfire. I honestly think he's stumped. Then he just went on about how, "It's just one of those 6.0's!"

 

[iamdub]

Whether-or-not he's stumped is beside the point. He's telling you stories, and not very good ones at that. I understand you may feel obligated to be loyal to him because you feel he "did you right" in the past (and maybe he honestly did). But, people and their lives change and you don't know what's going on behind the scenes. This, and you not being keen on such mechanical aspects puts you in a vulnerable position. If he's having issues of any kind, that's fine but not your problem and you shouldn't have to pay for them with the inconvenience of not having your car for so long and especially not with your wallet. Again, that doesn't matter because it's speculation at this point. When you focus on the facts, well, at least assuming what you have told us are the facts, it clearly appears that you are being yanked around. Trust is earned, not given, and any trust this guy may have earned from me would've been lost weeks ago.

Red flags based on your input:

- He said it had low compression in cylinder #6, even gave a specific psi, and that he saw the piston not reaching TDC. You're finding his stories as "weird" and you're doubting your trust in him at this point.

- Two weeks later, he seems to not recall his previous "diagnosis" (Okay, we'll give him a week due to the uncontrollable circumstances, but what all happened the week prior and why does it sound like this is the first time he's seen you and your car?)

- Week three, and now it "may not be anything more than a bad injector"? (Why is it still not diagnosed and how can he say that when he told you a couple weeks before that HE SAW low compression and HE SAW the piston not reaching TDC?)

- Latest word is that "there was a 'little' issue with the head and now it's getting compression". (So, the piston is magically reaching TDC now? What was the "little issue with the head"?)

- Says "It's just one of those 6.0s!" (Sounds like a weak attempt to dismiss his incompetency and/or wrongdoing and/or guilt.)


I see nothing trustworthy about the whole situation and I stand by my previous reply.

 

[swathdiver]

Where do you live Jim?

Any responsible mechanic with a shop will have a full featured scan tool to diagnose the engines he works on. If he had a Tech2, within minutes it could tell whether your problem is an injector a bad cylinder.

When I was a kid and got my first car, the "family" mechanic told me my engine was shot and that he would not let me drive out of there. He thought I had deep pockets like my uncle's and he'd been ripping them off for years. Probably because they were always drunk. Anyway, I backed him down and drove my car home. Two more con-artists and nearly a thousand dollars later and I'd learned my lesson, work on it myself!

If you live near me, I'd happily check it out for you. My advice is to get it out of there immediately. If none of us can check out with our scan tools, take it to the dealer. Their mechanics were trained to work on your specific car and can diagnose it usually within minutes.

 

[tiktok4321]

I live near Savannah, GA.

He has the latest Tech II Scan Tool - and my Tahoe being a Hybrid, he is well versed in the "deep codes" for the Hybrid system as well.

As much I hate getting yanked around by this guy, unfortunately my dealer isn't any better. With a stuck lifter, my dealer wanted me to buy a new engine for $9,000. This guy replaced all the lifters on even cylinder side, all labor, gaskets, new lifters & bolts for $1600.

He's had the truck since Labor day. Even taking a week off for the little storm we had, he's had 14 working days to figure it out.

Just talked to him on the phone and talked about some of the discrepancies of the conversations. He is trying to save me a butt load of money - which I appreciate. He said it runs "1000 times better". So now it's running at around 120 psi vs 135. He believes that's enough for a regular fire. But it's still occasionally misfiring. As far as the previous 45 psi to today's 120 psi, he says he checked the valves to ensure they are sitting proper and - I want to say he said he shaved the block a bit to ensure better header contact.

He also downloaded the latest firmware from GM (Not cheap for him to do) and updated the control modules (maybe not necessary for this fix, but it could help some other issues I was having).

He knows my frustration. He said he's more frustrated than I am. I don't need the car right now, but I need it fixed.

Ugh.

 

[iamdub]

120 and even 135 is low compression for a healthy LS. I'd let 135 slide if all cylinders read that and were within 10-15% of each other.

So, he pulled the head to check the valve seating (which should be fine since he "did a full head/lifter job just 4 months ago")? While the head was off, he decked the block with it still in the car, rotating assembly in place and all? Impressive.

The PCM records the misfires it detects and there should be freeze frame(s) related to this failure. His TechII should be all that's needed to quickly track down the cause of an intermittent misfire, if that really is all it's doing.

His stories still aren't adding up.