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RPMs drop when shifting the transmission into gear?

Tiny
ALEX25467
  • MEMBER
  • 2012 FORD FUSION
  • 2.5L
  • 4 CYL
  • AUTOMATIC
  • 165,000 MILES
When idling everything is fine. When I shift into gear rpm drops under 500 and to 0. The engine then shuts off and I have to restart. If I press gas to increase RPMs before/while shifting, the rpm still drops but not low enough for the engine to shut off and I can drive normally until I come to a stop. The car is fine at high speeds and when floored. I have replaced the engine and transmission mounts, one was broken, as well as the spark plugs, engine coils, and fuel pump. The problem still persists.
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Tuesday, July 2nd, 2024 AT 6:15 PM

22 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,772 POSTS
Hi,

When driving and coming to a stop, does the engine stall as if you are driving a vehicle with a manual transmission and not pressing the clutch?

I ask because the torque converter may be starting to fail. That is what releases the transmission and engine when you stop.

Also, before you put it in gear, what are the engine RPMs? Has the check engine light turned on?

Let me know.

Joe
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Tuesday, July 2nd, 2024 AT 7:51 PM
Tiny
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I have never driven a manual transmission, so I don't know. RPMs are around 1100-1200. The check engine light has not turned on. I had AutoZone use their OBD scanner and no codes came back except for something about the ABS.

Thanks for the response.
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Tuesday, July 2nd, 2024 AT 8:50 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

The RPMs are a bit high for idle. Have you checked to see if there are any engine vacuum leaks? That can cause an unstable idle.

If you haven't, here is a link that explains how to check. Do this and let me know the results.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know.

Joe
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Wednesday, July 3rd, 2024 AT 7:41 PM
Tiny
ALEX25467
  • MEMBER
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I am still running through some tests, I am not sure what my vacuum pressure should be or how to use that tool on my specific car, so I am still looking for those things. However, I did spray some WD40 in some places, not hearing anything though, and opened the oil intake cap while the engine was running, I only felt air blowing out.

But for some reason from doing those, the RPMs dropped to around 800 at idle. It still has the same problem but, it shakes much less and doesn't immediately drop the rpm to 0 after shifting into gear. It still does drop and shuts off but it is less violent and pressing the gas after shifting is enough for it not to shut off.
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Friday, July 5th, 2024 AT 10:51 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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If you connect a vacuum gauge to an intake port, at idle, you should have between 14 in and 20 in hg.

As far as the pressure coming from the oil cap, to a degree that is normal, but if it is excessive, check to make sure the PCV hose or valve isn't plugged.

Joe
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Saturday, July 6th, 2024 AT 9:39 PM
Tiny
ALEX25467
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It started around 20 and in about 30 seconds jumped to 26hg and stayed there.

The car also starts its idle around 1100-1200 but after a couple minutes it will drop down to 800 or so.

This is the port I used to test it. It seemed right but honestly, I didn’t know what to use and couldn’t find any specific answers.
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Thursday, July 11th, 2024 AT 12:05 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

What you used is fine. As far as the issue, the throttle body is what controls the idle speed via a signal from the PCM. I know you had it scanned at AutoZone, but I have to recommend having a CAN-scan done.

CAN stands or controller area network. Basically, the different modules are connected via a few wires, and they communicate with each other. This type of scan will retrieve codes regardless of the module storing them.

Here is a link that shows how it's done:

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Let me know if that is something you could have done.

Joe
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Thursday, July 11th, 2024 AT 8:50 PM
Tiny
ALEX25467
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I got a scan and these are all the codes that came up.

Power Train Module
1. P1000:00-2B. OBD Systems Readiness Test Not Complete.

Anti-Lock Brake System
1. C1280:20 Yaw Rate Sensor Signal Fault.

Instrument Panel Control Module
1. B10D7:51-08 Passive Anti-Theft System Key
2. U0161:00-0A Lost Communication with Compass Module

Generic Electronic Module/Smart Junction Box
1. B213A:20 Digital Dimmer Switch Input Circuit Failure

Heating Air Ventilation Conditioning
1. U0423:68-08 Invalid Data Received from Instrument Panel Cluster Control Module
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Sunday, July 14th, 2024 AT 6:20 PM
Tiny
JACOBANDNICKOLAS
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Hi,

I noticed we haven't made contact with you in a couple of days. I apologize for that.

As far as the cords are concerned, I'm struggling to see how they would cause the engine to stall. The one code I had hopes with is the C1280, but that isn't showing up for this vehicle. If possible, let me know the VIN number so I can look deeper.

On the other hand, I suspect something may be related to the torque converter not functioning properly. However, there are two different transmissions listed when I go to testing. (See pic below) Do you know which one you have?

Let me know.

Joe

See pic below.
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Tuesday, July 16th, 2024 AT 7:24 PM
Tiny
ALEX25467
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No worries, I appreciate ya'll helping me out! I drove it around a little and did the test again and these are the codes I got this time.

VIN: 3FAHP0JA9CR225338

I think it is a 6F35 but I don’t know for sure. I’m going to spend some time trying to find out and update if I find anything out.
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Wednesday, July 17th, 2024 AT 12:17 PM
Tiny
JACOBANDNICKOLAS
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Hi,

Okay, just FYI, based on your VIN, you have two open recalls needing attention. Both are related to the airbags. See pic 1 below.

Next, the P06B8 is related to the PCM's programable read only memory. I suspect that needs to be addressed first. Take a look at pic 2 below.

Let me know your thoughts.

Joe
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Wednesday, July 17th, 2024 AT 7:34 PM
Tiny
ALEX25467
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Thanks! I am aware of the recalls and I've tried to have ford fix them but I had a terrible experience when I talked to them about it but it might be time to try again.

That sounds good to me. I have an otofix D1 lite that I am borrowing (if that helps) but don't know how to flash the EEPROM.

Should I look at the PCM for corroding and other obvious issues? I don't know where it is at on this car but could take a look if you can guide me.

Is there also a repair manual or something like that to assist me in finding these parts on the car and how to get to them? That seems to be half the problem most of the time.
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Thursday, July 18th, 2024 AT 12:13 PM
Tiny
JACOBANDNICKOLAS
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Hi,

Yes, it would be a good idea to check all connections. If you do disconnect the PCM, first disconnect the battery. Don't reconnect the battery until the PCM is reconnected.

As far as the location, it is under the hood on the driver's side. It will be located very close to the firewall. I attached a picture below showing its location.

The manual I use is an online manual. You can access it, but they charge for use and it isn't too cheap. It is Alldata. Type that into a Google search and you'll find it.

On the other hand, if you let me know what is needed, I will try my best to get it for you free of charge.

Let me know.

Joe

See pic below.
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Thursday, July 18th, 2024 AT 7:37 PM
Tiny
ALEX25467
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So, I disconnected the three ports (I don’t know if one of those is the PCM or if that’s exactly where it was [videos 1 and 2]) and everything seemed fine for the most part (this part didn’t seem great but looks like just the casing and I think the wires are fine and intact. [Picture 1 and 2]).

I reconnected everything and scanned again and the code went away, and these are the codes remaining (Picture 3).
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Friday, July 19th, 2024 AT 1:21 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,772 POSTS
Hi,

I agree, the pins in the first two videos look okay. Just make sure none of them are cracked. Pics 3 and 4 don't look so good. Where is that harness going to? I copied your pic 4 and circled a spot. That appears to be where a connector should be, but it appears that only wires are going into one side of the socket. Also, are any of the wires damaged in the bunch I have an arrow pointed?

Joe
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Saturday, July 20th, 2024 AT 10:29 PM
Tiny
ALEX25467
  • MEMBER
  • 13 POSTS
It looks like it goes to the A/C line so I thought maybe a sensor. All the wires look fine and I was thinking of using some electrical tape to give them some protection.

I also don't see a picture.
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Sunday, July 21st, 2024 AT 4:03 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

I am sorry. I forgot to add the picture. I attached it below.

Let me know.

Joe
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Sunday, July 21st, 2024 AT 6:58 PM
Tiny
ALEX25467
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This video shows where it is going.
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Tuesday, July 23rd, 2024 AT 3:11 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,702 POSTS
Thanks for the video. The wiring looks okay to me, I would service the throttle body to help fix the problem. Here is a guide to help us with instructions below for your car:

https://www.2carpros.com/articles/throttle-actuator-service

Check out the images (below). Please let us know what happens.
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Thursday, July 25th, 2024 AT 9:55 AM
Tiny
ALEX25467
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Throttle body serviced. It wasn't extremely dirty but it is clean now. It seems to not have changed the RPMs at idle.

Over time it seems like the RPMs start even higher. Starts at around 1700 then very quickly drops to 1200 and then slow drops to 800 over the course of a few minutes. Cleaning hasn't seemed to change anything.
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Sunday, July 28th, 2024 AT 10:30 AM

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