• Sign Up! To view all forums and unlock additional cool features

    Welcome to the #1 Fiesta ST Forum and Fiesta ST community dedicated to Fiesta ST owners and enthusiasts. Register for an account, it's free and it's easy, so don't hesitate to join the Fiesta ST Forum today!


Persistent problem with car breaking up under load

Messages
23
Likes
13
Location
Burke
#1
So after installing a Sub and amp the other day after letting my car sit for about two weeks I had some weird issues/problems when I started her back up.

Initially had to jump her and on first start up, I went to go into first let out the clutch and gave her gas but got no response from my gas pedal. Checked to make sure my power line from my sub wasn’t blocking anything, As I went through the fire wall but saw nothing in the way. Turned my car off, went to turn it back on and the battery died. Weirdly wouldn’t jump at first but after fidgeting with the jumper cables a couple times it finally did. Once I got it jumped again, my gas pedal responded and I was able to start moving. Shortly after driving a short distance out of my neighborhood in first at low rpms, I got out on the main road and as soon as I got around 2500 rpm’s in first the power started breaking up and dropped down to a low idle then the motor shut off as well as white smoke out the back. Struggled to start back up, like it wouldn’t turn over just kept cranking then when it did it idled super low.

The below pictures are the codes it threw:

After reading a bit over night, I saw it could be as simple as reflashing the ECU. Tried that today, car started up fine but like the day before as soon as I got to 2,500 rpm’s it started breaking up. Didn’t stall out or die but happened every time I got to the same general RPM area.
I also read it could be the gas pedal position sensor. Battery holds a charge and charges fine, reading 14.5v while on.

Any insight is greatly appreciated, hoping it’s a simple fix before I drop 200$ on a new sensor.
 


Attachments

OP
Mcsmiff
Messages
23
Likes
13
Location
Burke
Thread Starter #3
Ive had the problem prior with it breaking up under load but it went away after doing it maybe once or twice. Originally what I thought had caused it was a bad coil boot, got a new ignition coil and it went away but now it’s back.

I'm guessing the sub install has something to do with it.
 


TyphoonFiST

9000 Post Club
Premium Account
Messages
11,516
Likes
8,009
Location
Rich-fizzield
#4
What kind of coils did you install? Parts store brand? fomoco brand? I cant say this enough... ALL Coils should just be replaced every 50-75k as overall maintenance as the windings break down over time and aren't able to transmit power as precisely as when new .Just like o2 sensors get dirty and become less responsive due to dirty exhaust over the thousands of miles driven.
 


Ford ST

2000 Post Club
Messages
2,921
Likes
3,053
Location
Pleasant Garden
#5
I would definitely check the wires around the accelerator pedal. Follow the wires if you can. This has nothing to do with Ignition you have a code for the accelerator pedal. Obviously something is wrong with the accelerator pedal. With a scan tool that can read accelerator pedal position you could see if pedal is communicating throughout its entire range.

"So after installing a Sub and amp the other day after letting my car sit for about two weeks I had some weird issues/problems when I started her back up."
This tells me obviously something was damaged during your install if the problem did not exist until you did this work that is what did it.

Sent from my SM-A526U using Tapatalk
 


Last edited:

TyphoonFiST

9000 Post Club
Premium Account
Messages
11,516
Likes
8,009
Location
Rich-fizzield
#6
Where did you ground and power the Amp from also?

Sent from my SM-N975U1 using Tapatalk
 


OP
Mcsmiff
Messages
23
Likes
13
Location
Burke
Thread Starter #7
Ive had the problem prior with it breaking up under load but it went away after doing it maybe once or twice. Originally what I thought had caused it was a bad coil boot, got a new ignition coil and it went away but now it’s back.
Where did you ground and power the Amp from also?

Sent from my SM-N975U1 using Tapatalk
Where did you ground and power the Amp from also?

Sent from my SM-N975U1 using Tapatalk
Power is from a 4ga line ran directly to the battery and ground is from an open hole from where I removed the rear seats.
 


OP
Mcsmiff
Messages
23
Likes
13
Location
Burke
Thread Starter #8
What kind of coils did you install? Parts store brand? fomoco brand? I cant say this enough... ALL Coils should just be replaced every 50-75k as overall maintenance as the windings break down over time and aren't able to transmit power as precisely as when new .Just like o2 sensors get dirty and become less responsive due to dirty exhaust over the thousands of miles driven.
I replaced all 4 with lower mileage oem coils that had maybe 40,000 miles on them. I’ve been suspecting it’s the coils going as well though to be honest by how it breaks up under power right around the same RPM.
 


TyphoonFiST

9000 Post Club
Premium Account
Messages
11,516
Likes
8,009
Location
Rich-fizzield
#9
Power is from a 4ga line ran directly to the battery and ground is from an open hole from where I removed the rear seats.
You routed the power wire through the fire wall correct? If so....did you have to unplug anything to move things out of the way to get it through?

Sent from my SM-N975U1 using Tapatalk
 


TyphoonFiST

9000 Post Club
Premium Account
Messages
11,516
Likes
8,009
Location
Rich-fizzield
#10
I replaced all 4 with lower mileage oem coils that had maybe 40,000 miles on them. I’ve been suspecting it’s the coils going as well though to be honest by how it breaks up under power right around the same RPM.
What is your current mileage?

Sent from my SM-N975U1 using Tapatalk
 


OP
Mcsmiff
Messages
23
Likes
13
Location
Burke
Thread Starter #11
You routed the power wire through the fire wall correct? If so....did you have to unplug anything to move things out of the way to get it through?

Sent from my SM-N975U1 using Tapatalk
I’m 99% sure I didn’t, I had already made a small hole through it next to the symposer line for my light bar switch setup and so I just pushed the rigid 4ga wire parallel through it til I made it into the bay and pulled what I needed from the engine bay outwards. Checked all my cables and plugs today after work to verify. Power line was kinda close to the clutch relay/switch so I moved that but no cables looked nicked or pulled out.
 


TyphoonFiST

9000 Post Club
Premium Account
Messages
11,516
Likes
8,009
Location
Rich-fizzield
#12
I’m 99% sure I didn’t, I had already made a small hole through it next to the symposer line for my light bar switch setup and so I just pushed the rigid 4ga wire parallel through it til I made it into the bay and pulled what I needed from the engine bay outwards. Checked all my cables and plugs today after work to verify. Power line was kinda close to the clutch relay/switch so I moved that but no cables looked nicked or pulled out.
Do you still have your symposer hooked up or did you disconnect it? You could've maybe ran the wire through that I do believe.

Sent from my SM-N975U1 using Tapatalk
 


Messages
21
Likes
34
Location
Leavenworth, KS, USA
#13
Have you had the sub/amp hooked up the whole time while trying to troubleshoot this?

I’d start with removing the in line fuse that powers the amp and see if the problem still persists. Also what did you tap into for a signal to the amp?
 


OP
Mcsmiff
Messages
23
Likes
13
Location
Burke
Thread Starter #14
Do you still have your symposer hooked up or did you disconnect it? You could've maybe ran the wire through that I do believe.

Sent from my SM-N975U1 using Tapatalk
67,000mi
Do you still have your symposer hooked up or did you disconnect it? You could've maybe ran the wire through that I do believe.

Sent from my SM-N975U1 using Tapatalk
Symposer is removed, I tried running it through the symposer line but couldn’t get it to go through so I gave up on that option.
 


OP
Mcsmiff
Messages
23
Likes
13
Location
Burke
Thread Starter #15
Have you had the sub/amp hooked up the whole time while trying to troubleshoot this?

I’d start with removing the in line fuse that powers the amp and see if the problem still persists. Also what did you tap into for a signal to the amp?
yes I’ve kept my amp and sub hooked up the entire time. I’ll try that today. I’ve spliced into the right rear speakers through the passenger’s side, opposite side I ran my power line.
 


Similar threads



Top