No codes, power loss

[Rocket Man]

I had a random misfire on my Denali for months, and sometimes while at idle it would nearly die before catching again and go back to running fine. It was almost like the ignition was being switched off and back on. It never threw a code. Turned out to be the MAF sensor. I tried cleaning it , but the problem remained until I replaced it. It was actually Blackbear Performance that clued me in- I sent them a datalog from my Autocal so they could send me a tune, and they said my MAF data was all over the place.

 

[jfoj]

A decent mechanic should be able to see this while viewing Live/Realtime data. But my $4 Android App will also Log all the data as well. I review Log files all the time on other forums.

 

[blackhawk17]

Well, it was. It would've been more if I'd bought his fuel pump. He marked up his fuel pump so I bought my own that came with a better warranty and just had him install it. So with almost 2 weeks worth of searching for the problem, and then actually replacing the fuel pump, the labor was over 500. So plus the fuel pump about 900.

For nothing.

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[blackhawk17]

I do think he had the computer hooked up when driving around, because he mentioned that he couldn't get it to act up for a while.

The other thing he mentioned was that there was a "noise" coming from the engine that was not normal. He couldn't identify it, but he said that if the knock sensors were picking it up it might retard the timing enough to cause the issues, to include the occasional miss.

Has anyone ever experienced this with maybe a bearing going out our something?

I'm going to get that app and order the Veepeak from Amazon, I'm just not sure how I'll look at it from here.

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[jfoj]

So if the knock sensors are picking up any kind of knock or noise, it can retard the timing and cause a loss of power and sometimes this may feel like a partial misfire. BUT, again, the timing could be easily monitored and graphed on most decent scan tools. A 3 degree reduction in timing can be felt in the seat of the pants, more than 3 degrees retard is very obvious.

As for strange noise, this may be an exhaust leak due to exhaust manifold bolt breaking. These engines are FAMOUS for the exhaust manifold bolts breaking. Very easy to check, just look for missing bolt heads at the end most bold positions on the manifold. I had both of my rear most bolts break on my Denali. I ended up installing repair brackets because these bolts are a PITA to access in the vehicle.

As far at looking at data remotely, this is not a problem. The OBDFusion App has DropBox integration built into the App. This is not hard to set up, but it will be tricky to get things moving because you will need to wife and/or family member or friend to set up the App on their end. You can set up the DropBox account on your end easily. Just do not do is yet until I post some info because DropBox attempts to install software on your computer that will then start to sync files from you computer and quickly fill up DropBox so you will then need to buy extra space!! Just a PITA sales technique. You can just have to be smart and not install the DropBox software.

Once DropBox is set up, you just need the user name and password for DropBox added in the App.

The App takes a while getting used to. I will see if there are some other options where you could do more remotely.

But once the App is configured, it can Log when the car is driven, then the Log files need to be sent to DropBox and you can review them. This along with Diagnostic Reports that will have Trouble Codes, Freeze Frame and Mode $05, $06 and $09 data.

If the wife will work with you on this, it will be VERY helpful.

 

[jfoj]

BTW, what phone/tablet platform are you going to be dealing with? Android or iProducts?

Keep in mind you may be able to get the wife to use the phone to video things so you can see what is going on and/or use a video chat program.

So checking for broken exhaust manifold bolts can be done remotely by video if you do not have someone that can check this for you.

You need to get creative on how you share information remotely and you will need cooperation from the far end which I hope you can get.

When was the last time spark plugs were changed and do you think this might be an ignition coil problem? Often coils do not always trigger codes but can cause misfiring and loss of power. Even an App like OBDFusion might be tricky to identify a flaky ignition coil.

BTW, I have a 2005 Yukon Denali with the 6.0l and I have lost the 2 rear exhaust manifold bolts, my guess is you are missing some to. The exhaust leaks tended to be more obvious on cold start and while pulling away from a stop when the engine was cold. One stayed a bit noisy after the engine was warm. I think we need to rule in or out broken exhaust manifold bolts. If this is the engine noise and the mechanic has not found this one, time to more on to a different mechanic.

I have heard of knock senor problems and water on these engines, but I have never run into it first hand.

 

[jfoj]

Here is the last DropBox instructions I had put together, it has been a while, so I have no idea if DropBox has changed the way the account set up process works. But I have had no feedback or complaints lately.

You might as well do this for many purposed because DropBox is just a cloud based flash drive anyway.

DropBox Info

You need to set up a DropBox Free account and learn how to upload the .CSV files to it once you get OBDFusion working.

The easiest way it to set up a DropBox Free account from your computer.

BUT, WARNING - YOU DO NOT WANT TO INSTALL THE DROPBOX SOFTWARE. IT WILL DO SOME CRAZY THINGS IF YOU DO NOT DISABLE AND MANAGE IT.

Most people use their email address for the DropBox user name and then choose a password. Make note of this password as you will need it for both direct web access and configuring DropBox within OBDFusion.

What you do is during the DropBox Free sign up process, once you enter your user name and password, when the prompt shows up to download and install the software, just use the Back browser button. This will take you to your Account and then you can upload the files either directly from the phone once you enter the DropBox user name and password in the OBDFusion App.

Just make sure you do not download any of the DropBox software on your computer, if you do, it can be removed, but it is much better to skip the installation of any software you really do not want or need.

This is just one step of the process, but an important one.

 

[iamdub]

Ok, so fuel pump replaced- problem not fixed. He concluded that the pressure was good, but the volume was not.

Sooo, same problem, $900 later. Yay.

Maybe I'll have the MAP sensor looked at. I did install a CAI earlier this year with an oiled filter. Who knows, maybe that's it.

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I don't have much faith in this mechanic. I swear he isn't using a scan tool properly or to it's full capabilities. I just don't understand how a guy can get away with saying "your problem is _____. Pay me $*** and I'll fix it". You pay them $$$ to replace the part and there's no difference afterward. I think they should have to reinstall the original part and eat the labor.

Since you installed an aftermarket intake with an oiled filter, there's a chance that a connection could be loose in the intake piping after the MAF or that the MAF itself is dirty from oil residue.

 

[blackhawk17]

Yeah I thought about the MAP being sorry and asked my mother to have a look.

We both have Android OS devices.

Thanks for the info!

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[blackhawk17]

I already ordered the Veepeak and it's shipped.

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