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Author Topic: Help with loss of power  (Read 3559 times)

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Offline KappaSky

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Re: Help with loss of power
« Reply #25 on: January 19, 2021, 04:33:14 PM »
Steelmesh, thanks for your thoughts.
Considered that, brand new plugs. Pull them and adjusted the gaps. Opened them up to see if it would affect it any. Unfortunately no with a tighter gap and a wider gap.

Offline Steelmesh

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Re: Help with loss of power
« Reply #26 on: January 20, 2021, 06:29:58 PM »
Doesn't the LNF come with a fuel rail pressure sensor and WB02 on the stock ECU?  Those would be helpful in continuing your diagnosis. 
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Offline elff

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Re: Help with loss of power
« Reply #27 on: January 20, 2021, 06:34:05 PM »
Yes they do and HPT can log it. 

Offline KappaSky

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Re: Help with loss of power
« Reply #28 on: January 20, 2021, 07:44:42 PM »
Far from scientific, but my Aeroforce gauges are capable of displaying fuel pressure at the rail and A/F. Unfortunately, impossible to drive, force the hiccup and monitor the gauges at the same time (even with a passenger) Being able to log would be beneficial.


Offline MattM

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Re: Help with loss of power
« Reply #29 on: January 22, 2021, 08:54:15 AM »
100 percent know your issue as I had it for years!  If you go to performance autowerks website (or other vendor)  and buy the upgraded GM Stage 2 map sensors. Then you will need a new Trifecta tune for those sensors. 
Like I said I had that problem since day 1.  Last year I bought upgraded to the Trifecta custom cataloguing tune (you should too because they will take the difference between the canned tune you already bought and the custom tune which is well worth it).  So I catalogued this error for a year with them and they told me that at wide open throttle around 5100 rpms the base timing would go from the commanded 12 degrees of advance to 6 and go back and forth until redline.  This would feel like a kind of stutter.  Anyway they surmised it was the stock map sensors.  I even got brand new stock map sensors first to test it first and it still did it.  Well, after I got the new sensors and they gave me the upgraded tune (for those sensors)  the problem was gone immediately.
Btw make sure they send you the upgraded GM Stage 2 sensor tune BEFORE you put the sensors in bc you don't want to drive it without the correct tune.

Offline KappaSky

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Re: Help with loss of power
« Reply #30 on: January 22, 2021, 09:19:18 AM »
@MattM, well this is optimistic.
In the spring I was going to start swapping a few parts. The first was the MAP sensor. Was going to pull one of my wife?s car (it doesn?t have these issues, but isn?t tuned).  If that failed, I was going to put the base tune back in to see if the hiccup still happened at full throttle. Noting that the boost pressure will be lower than with the tune.

Although this is very plausible, I wonder why it suddenly has manifested itself. The tune has been in for about 3 years now. The only change was a Solo HFC, which I swapped back to the factory cat. No changes. I am assuming the parameters of the base tune or any tune for that matter don?t change on the fly?

Anyhow, if the base tune runs fine, I will reflash with the trifecta tune and see what happens.

Thanks for the write up and info.

Offline MattM

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Re: Help with loss of power
« Reply #31 on: January 22, 2021, 04:50:20 PM »
I have the selectable tune.  I did exactly what you are thinking about doing...I switched to a brand stock map sensor etc...even on the base tune it still did it.  Don't know why but once it starts with stock map it will continue regardless.

This is more than "optimistic" btw...  So....here is how similar this is...I have a, guess what, 2007 sky redline that also had a trifecta tune and also had a solo hfc...  I changed plugs 5 times and gaps countless time.  Got a new high flow fuel pump as well.  Swapped MAP sensors as well...So then I get the datalogging trifecta tune and it took them a while to pinpoint the issue, but they eventually found the the advance fluctuation issue I told you about.  I questioned them on the stage 2 map and tmap as well they just said they knew of a few folks that this fixes the issue.  They even tried to command MORE advance to see if the fluctuation went away but even though it was commanding 13 degrees it couldn't hold it.

Now here's the really really crazy kicker!!!  So it WONT throw a code until the map sensor does fail, but when it does this problem will go away!  I'll have to search what code I eventually got with my first MAP sensor but when I got it my car ran like a lambo!  Thats when I got my 13.6 with a check engine light lol.

I wish I would have kept the first MAP sensor bc I could have sent to you so you would get the code and then you could see how well it runs (to know you need the stage 2 sensors).

Offline MattM

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Re: Help with loss of power
« Reply #32 on: January 22, 2021, 05:54:56 PM »
Found the code it was P0107.  Also found two threads about the same issue on sky roadster forum (one was mine)
here is Bun1t's thread.  He mentions it running better after the code as well. https://www.skyroadster.com/threads/aftermarket-tune-map-sensor-fail.29595/#post-408573

Here is mine:
https://www.skyroadster.com/threads/why-do-i-have-better-performance-after-map-sensor-failure.96253/#post-1305529

Offline KappaSky

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Re: Help with loss of power
« Reply #33 on: January 22, 2021, 06:45:14 PM »
Now that is crazy odd, because I have the selectable tune as well. Thinking if I put it back to the base tune it would produce less boost and maybe not throw the hiccup. Unfortunately that want the answer. This whole time I was thinking it was a sensor and was going to systematically start swapping parts from my wife?s car. Parts would have been ?free? for the testing.

So if the answer is a 3bar, I?m going to need to go back to Trifecta and order an upgraded tune.  Lucky I kept the red tuning cable.

Anyone on here have recent experience with Trifecta? 

I?ll have a read of the links Matt. Thanks for your help on this.

Offline KappaSky

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Re: Help with loss of power
« Reply #34 on: January 22, 2021, 07:33:57 PM »
@MattM. Good read, everything sound familiar except it sounds like your power loss was more like a pulse or fluctuation?  My power loss is sudden and total loss of power. 

Offline MattM

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Re: Help with loss of power
« Reply #35 on: January 22, 2021, 08:37:03 PM »
Now that is crazy odd, because I have the selectable tune as well. Thinking if I put it back to the base tune it would produce less boost and maybe not throw the hiccup. Unfortunately that want the answer. This whole time I was thinking it was a sensor and was going to systematically start swapping parts from my wife?s car. Parts would have been ?free? for the testing.

So if the answer is a 3bar, I?m going to need to go back to Trifecta and order an upgraded tune.  Lucky I kept the red tuning cable.

Anyone on here have recent experience with Trifecta? 

I?ll have a read of the links Matt. Thanks for your help on this.
Well when It happened I'd usually let off.  It definitely felt like I hit a wall when it happened.

Yeah, it wasnt that long ago when trifecta did the datalog tuning for me.  If you tell them when the power loss starts they'll be able to tell you if the issue is related to advance issues or something else.  Btw it is normal for the stocker MAP to go bad once its tuned as well. 

Offline KappaSky

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Re: Help with loss of power
« Reply #36 on: January 22, 2021, 10:19:16 PM »
Matt, I?ve sent Trifecta an email. Will let you know what happens.
Thanks

Offline Gentleman Jack

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Re: Help with loss of power
« Reply #37 on: January 25, 2021, 03:30:54 AM »
Promising news!!!  Well done.
Make the right choices now

Offline KappaSky

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Re: Help with loss of power
« Reply #38 on: January 25, 2021, 11:13:21 AM »
It's a good starting point Gentleman Jack.  Fingers crossed!

Offline MattM

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Re: Help with loss of power
« Reply #39 on: January 26, 2021, 09:11:55 AM »
Hey Kappasky...Other thing I wanted to ask was when you feel it lose power passed 5000 rpms do you immediately let off?  Reason I ask is bc that's what I used to do, but Trifecta wouldn't be able to see that in the datalog (it would just look like you let off to them).  If you keep your foot on the gas to try to make it go passed 5000tpms does it buck somewhat?  Like it alternates between losing power then moved smoothly then loses power again?

Offline KappaSky

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Re: Help with loss of power
« Reply #40 on: January 26, 2021, 07:09:53 PM »
Hey Matt. Nothing after it stumbles. Starts to buck and instinctively I let off as not to destroy it.

Update from Trifecta...they were awesome. They offered up to review one of my logs. I explained that the car is in storage, so they said just to send it when I get the car out.

Offline MattM

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Re: Help with loss of power
« Reply #41 on: January 26, 2021, 08:38:29 PM »
Hey Matt. Nothing after it stumbles. Starts to buck and instinctively I let off as not to destroy it.

Update from Trifecta...they were awesome. They offered up to review one of my logs. I explained that the car is in storage, so they said just to send it when I get the car out.
That is perfect that you don't have to pay yet to let them see the datalogs.  With regard to the bucking I bet if you kept your foot on the gas you would feel it let up then accelerate then let up again..  It almost feels like a misfire (which is why you lifted off the gas)

Offline KappaSky

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Re: Help with loss of power
« Reply #42 on: January 26, 2021, 09:32:34 PM »
Looking forward to hearing what Trifecta finds. Now to wait out the winter.

Offline KappaSky

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Re: Help with loss of power
« Reply #43 on: October 03, 2021, 06:07:42 PM »
An update to this thread. I finally data logged the car and sent the files to Trifecta.
The response is as follows:

? The good news is there is no issue with your MAP sensor.  The ECM is producing the commanded amount of boost, however there is insufficient fuel supply, which is resulting in injection misfires.

More specifically, your low pressure fuel pump is not performing as it should. ?

? High pressure commanded is 15,000kPa (2205psi), but we are barely seeing 1530kPa ( 225psi ) actual.  This happens when the low pressure pump isn't supplying enough fuel for the high pressure pump to send to the engine.?

I would appreciate any comments. Find it strange that there are no codes.

Offline kgschlosser

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Re: Help with loss of power
« Reply #44 on: October 04, 2021, 12:21:05 AM »
That sounds like a possible problem. You are able to view the LPFP pressure if you have a scan tool that allows you to select PIDS that you want to check. If the scan tool asks the ECM for a list of supported PIDS the PID for the LPFP pressure comes back as unsupported.

PID 0x0A is for fuel pressure, on the base model this is the pressure of the fuel pump in the tank, on the GXP it is the fuel rail pressure so the HPFP.
I believe the LPFP is on PID 0x23. which odly enough is supposted to be the fuel rail pressure on direct injected engines. I think GM fumbled the ball on that one.

The equation to decode the data for that PID is
(10 * (A << 8 | B)) * 0.145038

Where A is the first byte in the data and B is the second byte (left to right). Using that equation will give you the PSI reading of the LPFP.

If whatever you are using to read the the PID doesn't accept bitwise operations (<<, |) then you can use
(10 * ((256 * A) + B)) * 0.145038

The LPFP should be producing >= 60 PSI


Offline kgschlosser

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Re: Help with loss of power
« Reply #45 on: October 04, 2021, 12:41:57 AM »
also not sure how they come up with 2205 PSI from 15000 kPa command pressure. 15000 kPa == 2175.5660701083 PSI the actual reading is off as well. 1530 kPa == 221.9077391510466 PSI

None the less I can see how there is an issue there.

You should have gotten a P0087 DTC and that DTC is accompanied by the dreaded "Reduced Engine Power" see in the diver informant.

The conditions that have to be met for the P0087 DTC to get set  are as follows.

DTCs  P0090, P0091, P0092, P0191, P0192 and P0193 are NOT set
Ignition 1 signal is less then 18.1 volts
Relative injected fuel mass is between 5.016 percent and 500 percent
DFCO (Deceleration Fuel Cut Off)  is not active
Engine RPM is > 25
Engine start temperature is > -48C
Monitoring is continuous once the above conditions are met for 2 seconds.

P0090 - P0092 are DTCs for the fuel pressure solenoid that is built into the HPFP
P0191 - P0193 are DTCs for the fuel rail pressure sensor

There needs to be a pressure difference difference of > 1500kPa (217.55660701083 PSI)  between the actual and command pressures for the DTC to get set.

I am not sure why the P0087 DTC is not being set. It should be. This is where an app like the Torque app and an ELM blueteeth OBD module would come in handy. You could log the commanded, actual and the LPFP so you can see what is actually happening.


Offline KappaSky

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Re: Help with loss of power
« Reply #46 on: October 04, 2021, 11:42:35 AM »
Thanks for the additional info kgschlosser.
Well there are worse things that I need to replace.
Car runs great under normal driving, can even get into some good boost as long as you ease into the throttle. Stabbing the accelerator will cause it to belch, stumble, back fire, etc. 

Looks like the low pressure in tank pump is the entire assembly, except the float?

Offline kgschlosser

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Re: Help with loss of power
« Reply #47 on: October 04, 2021, 12:08:41 PM »
You do not have to replace the entire  hangar assembly. I recommend that you don't so you won't have to worry about adjusting the float in order to get the gauge to work correctly. You can buy a generic in tank fuel pump from any auto parts store you want it to be able to pump at more then 70 PSI and I want to say the magic number for the volume is something like 280 LPH (Liters per hour) I would have to double check that number.

The way the low pressure system is designed is there is no return. There is a regulator located on the hanger assembly  and that regulator is supposed to keep the line that heads to he engine at 60 PSI. Anything in excess of that gets dumped back into the tank. You can use a 100 PSI pump if you wanted to and there wouldn't be an issue. So long as the pump can move a volume >= to the factory pump and the pressure is >= the factory pump you will be fine.

Should cost in the neighborhood of 80.00 for a lifetime warrantied pump. Or you can go with an AEM high volume pump if you wanted to.

Offline MattM

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Re: Help with loss of power
« Reply #48 on: October 06, 2021, 08:08:02 AM »
So, it does belch then?  Also, I am blown away that the ecu can tell fuel pressure isn't up to snuff and its causing the car to actually stumble/belch yet no codes are thrown.  Hell Id love to know what what the wideband is saying at this time when this happens.  I got a nice $120 dongle.  A very cheap android tablet in my car that pulls up the torque app and lets me see the wideband air fuel ratio gauge in realtime.  I just cant believe it was running lean enough to cause it to belch like that and no codes were thrown..

Offline KappaSky

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Re: Help with loss of power
« Reply #49 on: October 06, 2021, 09:10:21 PM »
Matt, I questioned the same thing.  Still wondering why there were no codes. They replied the LNF is sometime ?lazy? to set off DTC codes. In there experience they feel it is the low pressure in tank pump.

I questioned if it could be the HPFP, they said possibly.

Hope the picture loaded.

 

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