No codes, power loss

[blackhawk17]

jfoj,

I figured it out. Here's the link. We'll see if it works.

https://www.dropbox.com/s/im2ykq2p5wprz3c/10 Nov 16 Use this one.csv?dl=0

 

[jfoj]

Ok, I finally have an update! I emailed OCTech Service (OBDFusion people) finally and just asked a couple of questions, to which they responded literally within a few minutes.

Simple settings issues. I had the GPS turned off, and that was the main issue.

So that being said I have my first REAL log file. I'm trying to sort my way through it now.

Sent from my SM-N920T using Tapatalk

OCTech is one of the best for App support.

I personally suggest people turn of the Lat & Long function in the App so your location will not be identified.

It might have been a problem where the Lat & Long was listed under the GPS Items to Log and the GPS was not turned on and this was a conflict? I will try to find out what the problem was for my own interest.

 

[blackhawk17]

Well I deleted it out of the file that I shared, so I'm comfortable with it.

Sent from my SM-N920T using Tapatalk

 

[jfoj]

Well I deleted it out of the file that I shared, so I'm comfortable with it.

Sent from my SM-N920T using Tapatalk

Simple thing, although you are not the current end user, it to just Uncheck the Lat & Long settings under Log Setup, Select Items to Log, GPS and then uncheck Latitude and Longitude. However, sometimes Altitude can at times be useful if the vehicle is being operated in an area with rapidly changing elevations or if the vehicle supports a MAP sensor and I can then correlate the MAP sensor value changes with altitude.

I PM'ed you as well.

 

[jfoj]

Looking over the Log now. Will comment in a bit.

 

[jfoj]

From the first glance, I do not see anything that stands out and screams "problem".

But I also understand the problem is somewhat intermittent mostly at highway speeds.

A few items to note:

1. Engine coolant temperature looks good overall.

2. MAF so far on initial look appears normal.

3. Post-cat O2 sensor behavior looks normal so I do not question the catalytic converters at this point.

4. Pre-cat O2 sensor swings look normal.

5. I have a slight concern about the overall ignition timing at is seems to settle around -10 to -15 degrees at times, but this may be normal. Unfortunatly my truck is down for the moment so I do not have a good comparison. But the ignition timing is still hitting 25-30 degrees at times, so this is pretty typical.

I need a few additional changes to the App.

1. MAF reading needs to be changed from lb/min to g/s. Should be under Settings, Units, Airflow

2. Add the follow Items to be Logged. These can be searched if there is a search field at the top of the page. Use the term Input v and Control m to quickly find the options.
a. Input Voltage read by the scan tool - this may be the absolute last item on the list??
b. If the vehicle supports it, Control Module Voltage.

Since this problem is somewhat intermittent, if you can have your wife or whom ever is driving the vehicle to run the Logging every drive, then provide the Log when the problem(s) show up and also ask them to pay attention to approximately how far into the drive in minutes the problem(s) show up so I can hopefully narrow down on the problem window.

Intermittent problems are tough and all I can say is hopefully we can catch some data that will give more insight as to what may be going on. Sometimes I have to rule things out to then focus in on the problem area. Sometimes the problem does not scream out at you, it is often hidden or buried.

 

[blackhawk17]

Hey ... I get to be the first to say ... "Thank You For Your Service!"

That said ... it's still early and hopefully more knowledgeable members will be chiming in later! The "knock Sensors" would pull power timing and thus cause a loos of power but I'm almost certain they would throw a code if that were happening??

I'm new to these vehicles myself but I don't think there is a separate "Fuel Filter" as such??? I think those went away in 2000 on most/all FI engines?? Everybody seems to put the little sock thing on the in tank fuel pumps and calls it good??? I'd "assume" the mechanic checked the fuel pressure??? A bad/failing fuel pump could do this and I don't think that would throw codes??

The Knock sensor "not throwing codes" is kinda weird if they are failing ... but we just had a member that used the fancy Snap On stuff and he was able to "see" that the motor was pulling timing! And it was indeed a bad knock sensor!

See here:

http://www.tahoeyukonforum.com/threads/huge-hesitation-mechanically-inclined-please-help.84229/

Thank you Chip18,

I finally looked at your response and went and read through that entire thread, and it sounds AWFULLY familiar. For some reason your response never showed up in my Tapatalk app that I typically use for this forum. Well, dang it. I wish I was at home. I'd throw some sensors at it and see what happens. As it is I still have to pay someone for maintenance. Sucks.

 

[jfoj]

Blackhawk,

You can graph out the Ignition timing and see what is going on if the timing is being pulled too much for some reason.

I would probably limit OBDFusion to maybe 5-8 PID's to monitor to give a better response time for the timing changes. This can be very helpful, I used a different tool to monitor the timing on one my cars where the manufacturer screwed up the timing maps, and with an aftermarket tune stacked on top of a bad OE tune things were BAD. Was very clear as 30 degrees of timing was being pulled while attempting to accelerate.

2-3 degrees of timing loss can be felt in the seat of the pants, 30 degrees it like a total buzz kill.

Search around, I recall that some of the problems have to do with water getting into the knock sensors in the valley and causing issues.

 

[blackhawk17]

I just got off the phone with another local mechanic and he thinks it may be as simple as clogged cats, considering there are 170,000 miles on the stock ones, and the issue doesn't seem to present until the engine is fully warm.

I can't believe that I didn't already think of that already, but it would make perfect sense. It may not be the primary issue, but there's no way those cats DON'T need to be replaced anyway. So, I (meaning my wife) have an appointment for Monday.

Fingers crossed.....

 

[blackhawk17]

Additionally, I have had issues in the past with at least one of the knock sensors. I used to occasionally go under the hood with a sprayer and clean everything out. I like a clean engine bay, but every time I did it with the Tahoe it would give me the CEL for the knock sensor (can't remember what code it is). So I finally got smart and it has never come back. It would usually go out on its own after a couple of days (I'm assuming it was the water evaporating). However, the fact that I don't consistently have a CEL leads me to believe that they are not faulty. But then, based on the post listed above, I guess you don't necessarily have to have the CEL to have faulty sensors. Especially if its intermittent.

I still do go under the hood with my old Z71, and it's never caused me any grief. Dang newer cars.

 

[jfoj]

Blackhawk.

Can you get me 2 Logs, I will be able to get an idea if the catalytic converters are a problem by looking at the Post Cat O2 sensor behavior. I may not be able to tell you they are clogged, but I can tell you I think they are not clogged.

This could save you money and your wife quite a bit of time. I am not buying that the converters are clogged and giving intermittent loss of power, it could but I would expect many other symptoms.

I need a 4 minute warm idle and a steady highway cruise (45-60 MPH range) Log.

Converter problems really do not come and go, if the monolith is clogged, then they tend to stay clogged.

Read the updated PDF attachment.

 

[Rocket Man]

My clogged cats were an aggravating problem that took quite awhile to fully present themselves. I had several codes over a couple months that pointed to MAF, TPS, multiple cylinder misfires, etc. I would replace a part or clean something, then clear the codes and as long as it wasn't driven hard it would be fine until I hammered the throttle again or was going over mountain passes. Towards the end, if I shut it off and it cooled down it would be fine for short trips but once it got hot it would start doing it again; that's when I suspected the cats. A shop checked them for me and one was 60% clogged, the other 40%.

 

[retiredsparky]

Knock sensors and intake manifold gaskets ought to be a maintenance item after a lot of miles. The sensors are in a bad place, especially if the vehicle is in a cold weather state. Slush and salt getting into any electrical connection is a problem. Intakes on these engines are known problem areas. (Not the problem in this case, but you would replace the intake gaskets when doing the knock sensors).