Sudden rough idle

[greggo151]

Here are 2 logs...I think I got cold start and hwy together

https://www.dropbox.com/s/09thsabt9v...60209.csv?dl=0

https://www.dropbox.com/s/x6jbyqtond...62459.csv?dl=0

Lots of surging on take off...rumbled like a diesel.

Thanks, for the help

[upallnight]

Originally Posted by greggo151

Here are 2 logs...I think I got cold start and hwy together

https://www.dropbox.com/s/09thsabt9v...60209.csv?dl=0

https://www.dropbox.com/s/x6jbyqtond...62459.csv?dl=0

Lots of surging on take off...rumbled like a diesel.

Thanks, for the help

Look at the MAF flow rate and compare it with the engine RPM. Like I call it you need a new MAF.

[jfoj]

I really need a good 4 minute warm idle Log. Best to warm engine up and then connect the App and allow the engine to idle for 4 minutes, then close the App. Each time you connect and disconnect the App you will create a Log for that time period.

The 2nd Log posted did not have the engine running.

The fuel system status is in error and they Pre-cat O2 sensors are not looking happy.

Get a 4 minute warm idle Log and also check the fuses inside the DME box as well.

Something is not right and I do not have enough data to blame any one thing.

[greggo151]

Well after checking some other obvious stuff I took it to the shop this morning. I don't have the time to chase whatever is going on. I will share the diagnosis when I get it.

[bcredliner]

Originally Posted by jfoj

I really need a good 4 minute warm idle Log. Best to warm engine up and then connect the App and allow the engine to idle for 4 minutes, then close the App. Each time you connect and disconnect the App you will create a Log for that time period.

The 2nd Log posted did not have the engine running.

The fuel system status is in error and they Pre-cat O2 sensors are not looking happy.

Get a 4 minute warm idle Log and also check the fuses inside the DME box as well.

Something is not right and I do not have enough data to blame any one thing.

It's great when we understand in depth information but the key is translating those details into the level of knowledge of the audience. I think that is troubleshooting steps that anyone can do since we can't quantify the capabilities of anyone.

I would have started with troubleshooting to eliminate the MAF (as upallnight suggested) as the cause since OP had just cleaned it--probably not a coincidence problem started after cleaning the MAF. As an example, what did you use to clean the MAF? Did you spray the rather hidden wires? Are you sure the connection is seated? Is there a break in the wires to the connection? Did you unplug the MAF to see if there is a change in the idle. Is acceleration normal?

The basics that most anyone can do--how to eliminate causes such as-- air restriction, bad MAF, vacuum leak, low fuel pressure, no spark, etc.

[jfoj]

The MAF does not look all that suspect here. Again, trying to make a determination of any problem with a single snap shot of data is very dangerous. This is why more data can and is useful.

Cleaning a MAF rarely solves problems from my experience. Some may find this works, but often there may be other reasons the "cleaning" seems to help. Maybe this is because the MAF connector was disconnected and reconnected, maybe this is because a small post MAF leak was corrected by coincidence when the MAF was removed and reinstalled.

I have run into a few similar cases in the past few weeks where the Fuel System Status is in error and for some reason the O2 sensor Voltage is extremely low and not toggling because the fuel system is not operating.

Unfortunately at this moment I have not had any feedback on whether or not the problems were improved or solved.

The problem is it very hard to get a full picture about what is going on with a vehicle you cannot see or touch. I let the data tell the story and lead to a correction.

I also sometimes assume too much, think that someone has in fact gone over the basics when sometimes this is not the case. What I sometimes refer to the lookie, touchy, pokie, pulley test.

Regarding the data, when I have concrete information I will post links to graphs that the OP can download and post back to the thread and will explain what I have found and often may have before and after data so others can follow along and see exactly what was identified and corrected.

It takes a lot of my time and I have helped countless forum members on many forums. So sometime people need to be patient and understand where this all leads.

OBDFusion is a great App and is by far one of the best generic OBDII tool available. I am gald the OP purchased the App and used it. This App is far more useful than most people fully understand. You do not need to start with manufacturer specific tools, often they are no better and even limited in what they can do. More forum members need to do this and fully understand how to use the App and benchmark their vehicle performance.

[jfoj]

Here is a good example where Pre-Cat O2 sensors were lazy, no codes were every triggered and there may not have been any obvious problems. I do not recall all the details and exactly what we were attempting to resolve, but I think this graph is very self explanatory even to a novice person.

The Pre-cat O2 sensors were lazy, probably high mileage units that should have been replaced long before they were, but we were able to get the data, determine the Pre-cat O2 sensors were lazy and they get after data so we were able to compare a before and after case.

[bcredliner]

Originally Posted by jfoj

The MAF does not look all that suspect here. Again, trying to make a determination of any problem with a single snap shot of data is very dangerous. This is why more data can and is useful.

Cleaning a MAF rarely solves problems from my experience. Some may find this works, but often there may be other reasons the "cleaning" seems to help. Maybe this is because the MAF connector was disconnected and reconnected, maybe this is because a small post MAF leak was corrected by coincidence when the MAF was removed and reinstalled.

I have run into a few similar cases in the past few weeks where the Fuel System Status is in error and for some reason the O2 sensor Voltage is extremely low and not toggling because the fuel system is not operating.

Unfortunately at this moment I have not had any feedback on whether or not the problems were improved or solved.

The problem is it very hard to get a full picture about what is going on with a vehicle you cannot see or touch. I let the data tell the story and lead to a correction.

I also sometimes assume too much, think that someone has in fact gone over the basics when sometimes this is not the case. What I sometimes refer to the lookie, touchy, pokie, pulley test.

Regarding the data, when I have concrete information I will post links to graphs that the OP can download and post back to the thread and will explain what I have found and often may have before and after data so others can follow along and see exactly what was identified and corrected.

It takes a lot of my time and I have helped countless forum members on many forums. So sometime people need to be patient and understand where this all leads.

OBDFusion is a great App and is by far one of the best generic OBDII tool available. I am gald the OP purchased the App and used it. This App is far more useful than most people fully understand. You do not need to start with manufacturer specific tools, often they are no better and even limited in what they can do. More forum members need to do this and fully understand how to use the App and benchmark their vehicle performance.

Just for clarification, I was not saying the problem is definitely the MAF. I was saying since the occurrence of the problem was directly associated with the cleaning of the MAF I would start by cleaning the MAF again, check the wires, connector and air intake tube. I don't agree that cleaning the MAF rarely solves the problem. I do agree that it doesn't always and I have found any improvement to be temporary so it is time to order a new one when you have had to clean it.

I respect your primary reliance on data but I don't suggest to start there unless one is well versed using diagnostic equipment. And when they aren't take it to someone that is because of the learning curve. There are always simple, easy, low cost no cost troubleshooting that can be done without reading info or codes.

I assume you disagree so I suggest when you request more data it would be helpful if you include specific instructions how to do so as well as an order of priority. I know that would be informative and helpful to me. I do all my own work and I have no problem saying my only takeaway of the graph is that it is colorful and I am sorry to hear there is a earthquake in your area.

[jfoj]

I got your point. I have never had anyone not able to gather data. Sometimes they need some direction, but it is really not that hard.

I did spell out a lot of what was required to gather the data in this thread.

If you would like a detailed description of the graph and what it means, I would be glad to explain.

[bcredliner]

Originally Posted by jfoj

I got your point. I have never had anyone not able to gather data. Sometimes they need some direction, but it is really not that hard.

I did spell out a lot of what was required to gather the data in this thread.

If you would like a detailed description of the graph and what it means, I would be glad to explain.

It's not that hard if are interested and like doing so. It's probably my pea brain but I find it hard to learn anything but the basics and hard to remember that the last time I used it. I think I am far from alone in this camp or there would be more discussion about using diagnostics on the forum. I would be interested in an explanation of what the graph means but it won't help unless you explain step by step how to get there.