Inconsistent Throttle Pedal Output

[Mopwer]

Hello.

I have a 78 Dodge truck with a 2010 LX 5.7 hemi swapped in. Throttle body came with the engine but not the pedal. I'm using one from a Ram I believe. Had originally bought the pedal from a scrapper. I'm getting a miss or rough idle sometimes but definitely under part throttle miss or running rough. Occasionally I get a General Miss (P0300?) but not always. Just started doing this recently. Also replaced the used cam and crank sensors with new ones. Had used coils on it, but now SOS coils, no change. Plugs look perfect. WOT runs great.

I thought it might be the throttle body or pedal (still drive by wire) so I ran a check with the engine off and it appears that the output from the pedal is very inconsistent (up and down even with a steady press of the right foot) and doesn't go all the way to 100% as seen in the attached log. I thought it was a bad pedal and ordered a new one. Threw it in and I'm getting the same output. Did a relearn with both pedals. I did a similar check on the TPS by manually actuating the throttle blade and it produced a smooth curve in VCM Scanner.

Any guesses as to what is going on here? Attached my current tune too.

schriner 78 dodge truck 09 jeep gc 5.7L 6.4 WOT Demand 5-16-21.hpt
Throttle pedal.hpl

[Mopwer]

Here is a log of with the previous pedal. You can see how it isn't consistent. I don't see anything else that jumps out having the potential for causing the miss/stumble.

Part throttle miss.hpl

[McCloud]

Is the Pedal from a 2010? Which PCM are you using?

[Mopwer]

Application for the pedal (68043161AD) fits 2009 to current Rams. PCM is a 2009 Jeep GC 5.7.

[McCloud]

In your license information in the VCM editor does the PCM come up as NGC4? So where I'm going is pedal to PCM compatibility. Unless there is something specific in the original software load between the Jeep and the RAM the pedal should be compatible with the PCM.

[decipha]

Key take away here is that it 'just started doing this recently'.

Any incompatibility would have presented itself from the get go would it not ?

[McCloud]

Key take away here is that it 'just started doing this recently'.

Any incompatibility would have presented itself from the get go would it not ?

yes sorry if I missed that... I took a look at your tune and it seems the PHI settings where changed.. Did you change those?

[Mopwer]

Yes it does show NGC4.

PCM Info.JPG

[Mopwer]

Key take away here is that it 'just started doing this recently'.

Any incompatibility would have presented itself from the get go would it not ?

Sorry, just started acting up as far as the engine missing at part throttle. I don't recall if the accelerator pedal has always had that output or not. Just started looking at it due to the drivability issue.

[Mopwer]

yes sorry if I missed that... I took a look at your tune and it seems the PHI settings where changed.. Did you change those?

Just looked up PHI and believe it relates to the narrow band settings. I've attached the original file from the PCM as I received it from HotWire.

I had a tuner tune the truck (has a 6.4 cam and headers, only changes). I did update the shifting parameters to firm them all up. Also, I got the PCM from HotWires when I got their harness. They may have changed something.

2009 Jeep Grand Cherokee Overland 5.7 L. 8 Cyl.hpt

[Mopwer]

I just did another log with the trans in park and just bringing up the revs and holding it, trying to get it to act up. Engine wasn't warm yet, but I did notice that the throttle pedal voltage didn't drop out like the throttle pedal %. It was steady and close to the TPS voltage. So, I imagine that the throttle % is calculated, just not sure why it would vary so much when the voltage was steady.

You will also notice that while holding the throttle steady toward the end of the log, the rpms were dropping and rising. Didn't see the TPS or MAP vary much so not sure what was causing that.

Part throttle miss Park.hpl

[McCloud]

Just looked up PHI and believe it relates to the narrow band settings. I've attached the original file from the PCM as I received it from HotWire.

I had a tuner tune the truck (has a 6.4 cam and headers, only changes). I did update the shifting parameters to firm them all up. Also, I got the PCM from HotWires when I got their harness. They may have changed something.

2009 Jeep Grand Cherokee Overland 5.7 L. 8 Cyl.hpt

The PHI runs calculations to manage the TB airflow. I was looking at other 5.7 tunes and the settings were different but they were also from a GPEC2 so the math within the PCM could be different with the NGC4. I'm sure those are fine I just thought it was worth looking into.

[McCloud]

I just did another log with the trans in park and just bringing up the revs and holding it, trying to get it to act up. Engine wasn't warm yet, but I did notice that the throttle pedal voltage didn't drop out like the throttle pedal %. It was steady and close to the TPS voltage. So, I imagine that the throttle % is calculated, just not sure why it would vary so much when the voltage was steady.

You will also notice that while holding the throttle steady toward the end of the log, the rpms were dropping and rising. Didn't see the TPS or MAP vary much so not sure what was causing that.

Part throttle miss Park.hpl

It really seems like a mechanical issue. The fuel trims don't lead toward a vacuum leak as there is typically a lot of compensation. Since you have changed the pedal out I'm leaning toward the TB. If you have the tools you can check the volts and resistance at the TB. You'll have to look up the specs. Maybe check the wiring to make sure there are no breaks to cause a short. Maybe more people will pick up on this post and have more input, but based on the logs I do believe it is a mechanical/hardware issue.

[Mopwer]

Thanks for the input, McCloud. I originally was thinking it could be a cracked intake, but couldn't find anything obvious. Might remove it to take a closer look.

I'll throw a meter on the TB and check the specs.

[Mopwer]

I haven't been able to figure out testing the TB yet, but did find that my PCV hoses was collapsing under the vacuum. Replaced the heater hose that was on there with stiffer wall hose and fixed that. Didn't seem to make a lot of difference. Took another log (attached) and was trying to slowly increase throttle pressure and just off idle it was trying to die. Slowly increasing pedal input and it took quite a bit of input before it would start to accelerate (all in park). Noticed it smelled rich, so I'm guessing that maybe at least maybe one bank is maybe reading off or maybe an exhaust leak pre O2 sensor, but I'm not able to find one. The O2 sensors are new. Where do I find the fuel tables? Would like to see if one side has adjusted way off from the other (attached latest download from PCM and attached).

Rich 7-3-21.hpl

[McCloud]

I'm not familiar with the NGC4 PCM but it should still be under Airflow then Speed density then you should have VE bank1 and bank2.. Those should be the identical. Looking at the LTFTs it's running really rich... It's trying to pull a lot of fuel. And looking at you injector pulse width they are different from bank to bank.

[Mopwer]

Turned out being bad O2 sensors. My wideband was showing super lean when the narrow band was showing rich. Installed new O2 sensors and a new MAP (was cheap) and runs no issue. And my wideband agrees. Those were new sensors, too which threw me off.