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Hey guys, I have a 2013 Ford Focus st and I’m having problems with it, it cuts out at 5,300 rpm and won’t let me accelerate I have my foot all the way down and it slowly accelerates and I have no boost, I changed all the sensors and still have no Idea what it is and the car has stage 3 with a 2871r turbo on it, I’m currently running with stratified and my tuner has no idea what it can be, he said it has something to do with electrical but I have no idea that’s why I’m posting it here and hope you guys could help out. I have the video of it cutting out.
Thx
 

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Silly question, maybe, but have you checked the plugs and the gap they're set to? Should be between .026 and .028", so if they've opened up more than that, it could be causing the issue, especially if you're running more boost pressure than normal. How many miles on your current plugs?

Should be easy to check within just a few minutes, so let us know what you find. Good luck.
 

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Silly question, maybe, but have you checked the plugs and the gap they're set to? Should be between .026 and .028", so if they've opened up more than that, it could be causing the issue, especially if you're running more boost pressure than normal. How many miles on your current plugs?

Should be easy to check within just a few minutes, so let us know what you find. Good luck.
Yes they are gapped too .026 and they have like 80 miles on the plugs.
 

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Ahh.. that makes sense. If the Cylinder Head Temp sensor goes out it can throw the car into basically an "air-cooling" mode (Fail-Safe Cooling), which will limit power and cause it to basically run in 2-cylinder mode instead of running all 4 to keep the temps down. I could definitely see that limiting your rpm and killing your boost levels. Might just need a new CHT sensor.
 

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Ahh.. that makes sense. If the Cylinder Head Temp sensor goes out it can throw the car into basically an "air-cooling" mode (Fail-Safe Cooling), which will limit power and cause it to basically run in 2-cylinder mode instead of running all 4 to keep the temps down. I could definitely see that limiting your rpm and killing your boost levels. Might just need a new CHT sensor.
I’ve changed the sensor this weekend and still the same issue
 

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Is it still throwing the code? If so, then it still thinks there's an issue so it's keeping it in limp mode. Time to start chasing electric connections, if that's the case. Check chassis and the main ground cable from the battery to the stud in the engine bay. This is a low voltage sensor, so they're very susceptible to any grounding issues. According to this site: https://www.searchautoparts.com/motorage/powertrain-pro/diagnosing-fords-cylinder-head-temperature-cht-sensor , the sensor's ground is shared with the O2 sensor grounds. If the rear O2 sensor is having an issue and your tune is ignoring the rear O2 sensor (so it wouldn't show a failure even if it was bad), then that could possibly be a failure point. Just throwing out ideas... hope you get it sorted out soon.
 

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Is it still throwing the code? If so, then it still thinks there's an issue so it's keeping it in limp mode. Time to start chasing electric connections, if that's the case. Check chassis and the main ground cable from the battery to the stud in the engine bay. This is a low voltage sensor, so they're very susceptible to any grounding issues. According to this site: https://www.searchautoparts.com/motorage/powertrain-pro/diagnosing-fords-cylinder-head-temperature-cht-sensor , the sensor's ground is shared with the O2 sensor grounds. If the rear O2 sensor is having an issue and your tune is ignoring the rear O2 sensor (so it wouldn't show a failure even if it was bad), then that could possibly be a failure point. Just throwing out ideas... hope you get it sorted out soon.
Thx I’ll look there
 

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If the sensor was changed out, then I'd check continuity between the sensor wires and their end-points, both at the ECM and the ground points. Do you have a multi-meter that you trust to read resistance accurately?
 

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If the sensor was changed out, then I'd check continuity between the sensor wires and their end-points, both at the ECM and the ground points. Do you have a multi-meter that you trust to read resistance accurately?
No I don’t have a multimeter. Where can I get one and how much will it cost?
 

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Autozone/O'Reilly/NAPA/Advanced Auto Parts... any of those would have a multimeter. Really basic one will run you $15-20, and a Fluke or other high-end one could be $500+. Look around on those sites and see which have good reviews in the price range you want to spend and go pick one up. Would expect it to be less than $50, though.
 

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Autozone/O'Reilly/NAPA/Advanced Auto Parts... any of those would have a multimeter. Really basic one will run you $15-20, and a Fluke or other high-end one could be $500+. Look around on those sites and see which have good reviews in the price range you want to spend and go pick one up. Would expect it to be less than $50, though.
Okay, thx, and where do I check again?
 

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You'll need to find the CMT on your car (could probably find a youtube on changing it out, so you'll then see the location), and then check from the pins on the sensor connector to the ground location(s) as well as back to the PCM for the signal/power wire(s). You could also start the car and watch voltage on the sensor using the probes. Since it has two different resistors, you should see the voltages switch as the car comes up to operating temp. Regarding the grounds, if any of them are near a heat source (exhaust, turbo), it could cause the grounds to show higher resistance when they heat up. In other words, they might be fine when they're cool, but be out of spec when hot. Also, if any of the grounds are corroded, definitely re-do them by cutting/stripping off some of the corroded wiring and re-doing the ground point.
 

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Discussion Starter #16
You'll need to find the CMT on your car (could probably find a youtube on changing it out, so you'll then see the location), and then check from the pins on the sensor connector to the ground location(s) as well as back to the PCM for the signal/power wire(s). You could also start the car and watch voltage on the sensor using the probes. Since it has two different resistors, you should see the voltages switch as the car comes up to operating temp. Regarding the grounds, if any of them are near a heat source (exhaust, turbo), it could cause the grounds to show higher resistance when they heat up. In other words, they might be fine when they're cool, but be out of spec when hot. Also, if any of the grounds are corroded, definitely re-do them by cutting/stripping off some of the corroded wiring and re-doing the ground point.
Okay, thx
 

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If you do not have access to proper oem wiring diagrams, or know how to read them I would not attempt this as a DIYer. You can easily cause major PCM damage if tested improperly.. and do not shove paper clips into the terminals, you will widen them and cause resistance/ false readings. But I guess if you do know what you are doing, I can get you the diagrams, and description of operation
 

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If you do not have access to proper oem wiring diagrams, or know how to read them I would not attempt this as a DIYer. You can easily cause major PCM damage if tested improperly.. and do not shove paper clips into the terminals, you will widen them and cause resistance/ false readings. But I guess if you do know what you are doing, I can get you the diagrams, and description of operation
I know what I’ll be doing thx and that would be great if you provide it
 

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Hey guys, I have a 2013 Ford Focus st and I’m having problems with it, it cuts out at 5,300 rpm and won’t let me accelerate I have my foot all the way down and it slowly accelerates and I have no boost, I changed all the sensors and still have no Idea what it is and the car has stage 3 with a 2871r turbo on it, I’m currently running with stratified and my tuner has no idea what it can be, he said it has something to do with electrical but I have no idea that’s why I’m posting it here and hope you guys could help out. I have the video of it cutting out.
Thx
Are you in valet mode.
 
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