A Challenge For The Veterans

windrunner408 · Dec 14, 2011

Ok well I dont really care who can help me with this but am just hoping someone can. I have had a problem for a while that I can not for the life of me (or anyone else it seems so far) figure out what is going on.

The PROBLEM seems to manifest itself in the form of: I'll be cruising down the road say for 15 miles or so (say at 65-70 mph and with everything at normal operating temperatures) and then, like a switch, the truck seems to defuel and the boost level shoots up about 3-4psi and the truck feels like it has no power.

Now I can give you just about any parameter you would like to know. I have given these before on other forums but they seem to get me no where. I am hoping that through discussion of asking questions and trying different diagnosing techniques WE can figure out what could be causing this.

Any and all help would be GREATLY appreciated.

protraxrptr17 · Dec 14, 2011

I'm sure you have answered all this already, but..

Does it happen on stock tuning?

Any codes?

How do you get the power back? Do you just let off for a minute? Do you have to pull over?

What happens to your fuel pressure when this happens?

Any other strange symptoms that may seem unrelated?

windrunner408 · Dec 14, 2011

protraxrptr17 said:
I'm sure you have answered all this already, but..

Does it happen on stock tuning? It does happen on stock tuning.

The engine gets a little quieter like it isnt quite injecting the same amount of fuel as it was before.

Any codes? No codes.

How do you get the power back? Do you just let off for a minute? Do you have to pull over? I have to shut the truck off and let it cool down and then start it back up and go until it happens again. Once it happens it will stay there until I shut the truck off and let it cool down again.

What happens to your fuel pressure when this happens? Fuel pressure stays constant.

Any other strange symptoms that may seem unrelated? The engine gets quieter like not as much fuel is being injected. Also this problem did seem to only manifest itself when OAT/IAT was 80*F or higher but then it worked its way down to the mid 70s F and then today I noticed that it happened when IAT was 66*F. I do not notice it in the morning with OAT/IATs at least below 50*F

If I can provide more info just let me know. I have looked at A LOT of parameters with my CTS.

windrunner408 · Dec 14, 2011

Is there such a thing as limp mode for the ECM?? Because that is what it feels like my truck slips into. What could cause this??

protraxrptr17 · Dec 14, 2011

What does the ICP desired vs actual do when this happens?

Had a 7.3 doing this once and was kicking my ass. Had a leak in the line between the pump and the tank. It was sucking just enough air to build up and make the engine smother, but the gauge pressure never moved. Not saying this is your problem, but you can check it.

windrunner408 · Dec 14, 2011

I am not sure what ICP desired vs actual means or how to measure/monitor that. I know what ICP is but in your description of the 7.3L you lost me in "the line between the pump and the tank. It was sucking just enough air to build up and make the engine smother". Can you explain this a little further and what line you had that leaked??

protraxrptr17 · Dec 14, 2011

It was the fuel line between the tank and the electric frame mounted fuel pump. Put a couple pounds of air into your fuel tank for about 15 minutes and watch for drips.

My scan tool shows what ICP the PCM wants. I usually set it up to graph both of them. If the graphs do not mimic each other closely, you have a problem, such as regulator, hpop, leak somewhere, etc. Not sure if yours shows that.

DEEZUZ · Dec 14, 2011

windrunner408 said:
If I can provide more info just let me know. I have looked at A LOT of parameters with my CTS.

Well WTF than, answer the questions the guy asked????

protraxrptr17 · Dec 14, 2011

CTC DEEZUL said:
Well WTF than, answer the questions the guy asked????

HAHA! I thought the same thing until I looked up at where he quoted me.

windrunner408 · Dec 14, 2011

CTC DEEZUL said:
Well WTF than, answer the questions the guy asked????

Uh I am sorry, I have tried to answer his questions the best I know how to. His post didnt make sense until now. I am not a mechanic.

I dont know if the Edge CTS shows what he is asking for. I may have to wait until I get an AE scan tool to monitor things real time and see how things change when this conidition occurs.

DEEZUZ · Dec 14, 2011

are you ****ing kidding me?

you have to ask your CTS if the truck is a stock tune?

you have to ask it how to get the power back?

wtf is wrong with you?

Im outta here

windrunner408 · Dec 14, 2011

protraxrptr17 said:
HAHA! I thought the same thing until I looked up at where he quoted me.

Hey man, I am really confused here. Is there something that I am not providing you?? Maybe I was wrong about having monitored a lot of parameters. I dont know. I guess I was hoping someone would have heard of something like this happening before. I am willing to try anything you think I should to see if it leads to the diagnosis of the problem.

Sorry if I cant be of more help.

I am really just trying to figure out what could be telling the ECM to cause the turbo to boost up like it does.

I do have a question, if I am running more boost at the same rpm as before does that mean there is less fuel being injected than before?? Has the Air/fuel ratio changed??

windrunner408 · Dec 14, 2011

CTC DEEZUL said:
are you ****ing kidding me?

you have to ask your CTS if the truck is a stock tune?

you have to ask it how to get the power back?

wtf is wrong with you?

Im outta here

Ok Bro. PISS OFF then. You can come back when you can adequately express what i am not providing.

I provided the following to the original responder's questions. He asked the following:

Does it happen on stock tuning? I responded with - It does happen on stock tuning.

Any codes? I responded with - No codes.

How do you get the power back? I responded with - Do you just let off for a minute? Do you have to pull over? I have to shut the truck off and let it cool down and then start it back up and go until it happens again. Once it happens it will stay there until I shut the truck off and let it cool down again.

What happens to your fuel pressure when this happens? I responded with - Fuel pressure stays constant.

Any other strange symptoms that may seem unrelated? I responded with - The engine gets quieter like not as much fuel is being injected. Also this problem did seem to only manifest itself when OAT/IAT was 80*F or higher but then it worked its way down to the mid 70s F and then today I noticed that it happened when IAT was 66*F. I do not notice it in the morning with OAT/IATs at least below 50*F

If you have something useful to provide, please do, otherwise STFU and dont criticize the way I provide answers when you can't seem to even ask any question other than what is wrong with me. Like I have a F###ing disorder or something.

protraxrptr17 · Dec 14, 2011

I think CTC didnt see where you answered my questions. I didnt see it at first. You answered the questions I asked. Everything is cool.

I would ignore the boost until I got an idea of what the ICP is doing. The rise in boost is probably an effect of the power loss instead of a cause.

protraxrptr17 · Dec 14, 2011

Also take a look at the VREF PID. Especially when the power loss happens. It should be real close to 5 volts always. If not, it can make all kinds of problems.

windrunner408 · Dec 14, 2011

protraxrptr17 said:
I would ignore the boost until I got an idea of what the ICP is doing. The rise in boost is probably an effect of the power loss instead of a cause.

I would agree that the rise in boost is a side effect from a reduction in power production. As in fuel seems like it is being held back like a sort of limp mode to protect something.

protraxrptr17 said:
Also take a look at the VREF PID. Especially when the power loss happens. It should be real close to 5 volts always. If not, it can make all kinds of problems.

What is the VREF PID?? I have looked at Injection Control Voltage while it was happening at it read like 1.7v while cruising and .8v at idle. This was all after the switch happened.

My question if I monitor ICP with my CTS through the OBDII port, does it matter if my truck has a tune on it?? I have a TSD SPD tune and I know that by having that tune on it that it will skew the ICP readout. Should I return the truck to stock to get the "real" ICP??

protraxrptr17 · Dec 14, 2011

Yes, do your diagnostics with it stock.

Vref is the 5v supply generated by the pcm to supply alot of your sensors. If the Vref is not 5v all the sensors readings will be off.

windrunner408 · Dec 14, 2011

Oh yea that makes total sense about the VREF. I understand the importance of the reference voltage. I will have to return my truck to stock tomorrow and see what happens.

So just so I am correct here, with the truck on stock, I am looking for ICP to drop when this happens??

protraxrptr17 · Dec 14, 2011

I would just look for a change. The sensor may show a rise, and then the PCM backs it off when it didnt actually rise. Or the regulator is screwed up and loses control (if I had to guess this is my guess)