Ford Focus ST Forum banner
1 - 12 of 12 Posts

·
Registered
Joined
·
506 Posts
Discussion Starter · #1 ·
Alright guys, I know there is a sticky about idle fluctuations but my problem is the polar opposite of every response in there so i think it is something else.

The car, on almost every warm start ups will drop RPMs and shudder. Also, on cold starts sometimes the idle will hunt befoer settling at the elevated cold start RPM. But, with the AC OFF it will drop and shudder 80% of the time when i come to a stop (at a light/ in traffic/ parking). It has died on me a few times. The symptoms seem to happen any time it is above 50 degrees and the AC is OFF. Any ideas or suggestions?

It began doing this one day when i picked my car up from getting an oil change, and has persisted through multiple oil changes.

Again, in the idle fluctuation sticky everyone has a problem with the AC on, mine is the exact opposite and thus i decided to venture out into the world of starting my own thread.
 
  • Like
Reactions: lanssolo

·
Registered
Joined
·
235 Posts
Alright guys, I know there is a sticky about idle fluctuations but my problem is the polar opposite of every response in there so i think it is something else.

The car, on almost every warm start ups will drop RPMs and shudder. Also, on cold starts sometimes the idle will hunt befoer settling at the elevated cold start RPM. But, with the AC OFF it will drop and shudder 80% of the time when i come to a stop (at a light/ in traffic/ parking). It has died on me a few times. The symptoms seem to happen any time it is above 50 degrees and the AC is OFF. Any ideas or suggestions?

It began doing this one day when i picked my car up from getting an oil change, and has persisted through multiple oil changes.

Again, in the idle fluctuation sticky everyone has a problem with the AC on, mine is the exact opposite and thus i decided to venture out into the world of starting my own thread.
Maybe someone else can correct me if I'm wrong but I think the bcm reprogramming is supposed to fix that. There was a recall for bad idles and cars shutting off, I have a 15 and mine had that recall issued. Hope this helps

Sent from my SAMSUNG-SM-N920A using Tapatalk
 

·
Registered
Joined
·
506 Posts
Discussion Starter · #3 ·
Maybe someone else can correct me if I'm wrong but I think the bcm reprogramming is supposed to fix that. There was a recall for bad idles and cars shutting off, I have a 15 and mine had that recall issued. Hope this helps

Sent from my SAMSUNG-SM-N920A using Tapatalk
It was supposedly done a couple months ago(Unless there is a newer one). But as i said everyone else's problem occurs with the AC on and generally disappears when it is off. Mine is the polar opposite and operates fine when the AC is on but is wacky when i turn it off. When was your BCM flashed? Maybe there is another update that my dealer did not inform me of.
 

·
Registered
Joined
·
1,900 Posts
When was the last time you pulled your spark plugs? I'd check their gap (around 0.028") and general health. I'd also check if the car is covered by the engine harness splice recall/TSB and ensure that is performed. You can also check the grounds on the driver's side frame rail -- including the two under the battery tray. After the car sits overnight, I'd check the battery resting voltage to see if it's low. I'd also check the commanded system voltage on startup. It should jump above 15V for a few seconds, and then come back down to mid 14s. If it stays higher, you may have a bad battery. That's where I'd start.

Also, the idle hunting on warmup is not uncommon... There are tables that command to warm up the cat by increasing idle/richness; there are tables that command to lower the idle once the car starts to get sufficient water temp. One tuner advised me that the commanded idle speed from those sets of tables sometimes conflict during the entirety of the warmup cycle, so the car hunts. Blip the throttle and it should clear.

Similarly, turning on the AC increases the commanded idle speed, so I'd expect the idle to smooth out if you had a bad battery/ground etc.

Hope that helps,
Mark
 
  • Like
Reactions: lanssolo

·
Registered
Joined
·
506 Posts
Discussion Starter · #5 ·
When was the last time you pulled your spark plugs? I'd check their gap (around 0.028") and general health. I'd also check if the car is covered by the engine harness splice recall/TSB and ensure that is performed. You can also check the grounds on the driver's side frame rail -- including the two under the battery tray. After the car sits overnight, I'd check the battery resting voltage to see if it's low. I'd also check the commanded system voltage on startup. It should jump above 15V for a few seconds, and then come back down to mid 14s. If it stays higher, you may have a bad battery. That's where I'd start.

Also, the idle hunting on warmup is not uncommon... There are tables that command to warm up the cat by increasing idle/richness; there are tables that command to lower the idle once the car starts to get sufficient water temp. One tuner advised me that the commanded idle speed from those sets of tables sometimes conflict during the entirety of the warmup cycle, so the car hunts. Blip the throttle and it should clear.

Similarly, turning on the AC increases the commanded idle speed, so I'd expect the idle to smooth out if you had a bad battery/ground etc.

Hope that helps,
Mark
I changed out the plugs to one step colder at about 30k; im now almost at 40k and nothing ever changed. I believe the dealer did the splice when i first got the car (it arrived with a check engine light and they took it in and did the splice while they had the car). I sanded down the three main grounds and jumped the main ground to one on the frame rail. I have not checked the voltages at any time. TO measure the resting voltage i assume i just measure right off the battery terminals. How would i measure the commanded voltage? Thanks for all your insight, I assumed that is why my idle smoothed out with the AC on but didnt understand why it was the opposite of everyone else in the other thread.
 

·
Registered
Joined
·
1,159 Posts
This is an issue all ST suffer from. Check plugs most likely 2 and 3 opened up to .30 or more. Its a common issue. I usually gap mine to .26 drive about 1000 miles and regap them
 

·
Registered
Joined
·
235 Posts
It was supposedly done a couple months ago(Unless there is a newer one). But as i said everyone else's problem occurs with the AC on and generally disappears when it is off. Mine is the polar opposite and operates fine when the AC is on but is wacky when i turn it off. When was your BCM flashed? Maybe there is another update that my dealer did not inform me of.
Mine was done about 2 months ago. I also still have the stall shudder problem with the ac on. I have heard a lot about sanding down the grounds to get a better connection, some cases it solved the problem and some didn't. I'm going to do mine this weekend, hopefully it makes a difference

Sent from my SAMSUNG-SM-N920A using Tapatalk
 

·
Registered
Joined
·
506 Posts
Discussion Starter · #8 ·
This is an issue all ST suffer from. Check plugs most likely 2 and 3 opened up to .30 or more. Its a common issue. I usually gap mine to .26 drive about 1000 miles and regap them
They really get opened up that quick? That would mean I'd have to check them every week. Also, does your car not do this if you routinely regap your plugs? Changing the plugs had no effect on the idle for me

Mine was done about 2 months ago. I also still have the stall shudder problem with the ac on. I have heard a lot about sanding down the grounds to get a better connection, some cases it solved the problem and some didn't. I'm going to do mine this weekend, hopefully it makes a difference

Sent from my SAMSUNG-SM-N920A using Tapatalk
I sanded down the grounds, kinda stopped it for a little bit but then the computer relearned and started doing it again. It's pretty easy to do so not a big waste of time if nothing changes. I also jumped the ground on the shock tower to the frame rail while I was at it.


Tap Tap Tap...
 

·
Registered
Joined
·
1,900 Posts
I changed out the plugs to one step colder at about 30k; im now almost at 40k and nothing ever changed. I believe the dealer did the splice when i first got the car (it arrived with a check engine light and they took it in and did the splice while they had the car). I sanded down the three main grounds and jumped the main ground to one on the frame rail. I have not checked the voltages at any time. TO measure the resting voltage i assume i just measure right off the battery terminals. How would i measure the commanded voltage? Thanks for all your insight, I assumed that is why my idle smoothed out with the AC on but didnt understand why it was the opposite of everyone else in the other thread.
OK, a few things...

First _how_ the dealer did the repair splices may be important. On the earlier cars (I have a 2013), first there was TSB. The TSB called for replacing the splices with new crimp connector splices. Then there was a recall. The recall called for replacing the splices by soldering the wires together. There are other posts here from users who had the TSB repair done poorly. Even if one had the TSB done, the recall still gets done on Ford's nickel.

Second, the two grounds under the battery tray may need attention too... :)

Third, resting voltage sure you can take at the battery terminals, or just the positive terminal and the ground wire on driver-side the strut tower. Running voltage can be taken the same way, or with a Cobb AccessPort.

Hope that helps,
Mark
 

·
Registered
Joined
·
506 Posts
Discussion Starter · #10 ·
OK, a few things...

First _how_ the dealer did the repair splices may be important. On the earlier cars (I have a 2013), first there was TSB. The TSB called for replacing the splices with new crimp connector splices. Then there was a recall. The recall called for replacing the splices by soldering the wires together. There are other posts here from users who had the TSB repair done poorly. Even if one had the TSB done, the recall still gets done on Ford's nickel.

Second, the two grounds under the battery tray may need attention too... :)

Third, resting voltage sure you can take at the battery terminals, or just the positive terminal and the ground wire on driver-side the strut tower. Running voltage can be taken the same way, or with a Cobb AccessPort.

Hope that helps,
Mark
When i get home from work ill try and see if the paperwork mentions the method for solving the Splices. Also, are the two ground under the battery tray that same two that are on the frame rail? If so i sanded them and jumped it to the strut tower. The 3 ground i cleaned up were the strut tower, and two ground visible when you pull off the air box that are on the frame rail leading to the bumper support. I don't have an AP :crying: so i will have to measure the voltage from the terminals. Can I do this anytime i start the car up? Thanks again. hopefully it turns out my battery is shot, i have done almost everything; I have done so much research and anytime i find something that worked for someone else i go and do it to try and remedy the problem. The Ford dealers are no help; they took the car for a day when i gave them an entire week and said they could not replicate it and that was that. I left with the BCM reflashed but no change it idle fluctuation.
 

·
Registered
Joined
·
1,900 Posts
When i get home from work ill try and see if the paperwork mentions the method for solving the Splices. Also, are the two ground under the battery tray that same two that are on the frame rail? If so i sanded them and jumped it to the strut tower. The 3 ground i cleaned up were the strut tower, and two ground visible when you pull off the air box that are on the frame rail leading to the bumper support. I don't have an AP :crying: so i will have to measure the voltage from the terminals. Can I do this anytime i start the car up? Thanks again. hopefully it turns out my battery is shot, i have done almost everything; I have done so much research and anytime i find something that worked for someone else i go and do it to try and remedy the problem. The Ford dealers are no help; they took the car for a day when i gave them an entire week and said they could not replicate it and that was that. I left with the BCM reflashed but no change it idle fluctuation.
As re frame rail grounds, there are three wires going to two more grounds underneath the battery box. These two are _in addition to_ the grounds underneath the airbox on the same frame rail. Take a look at this pic: http://www.focusst.org/forum/attach...y-pc1200t-battery-installation-fixgrounds.jpg

Your paperwork should mention whether the repair was done under the TSB or under the recall; that will let you know how the repair was done (crimps or solder).

You can measure voltage anytime of course! You can get a cheapy VOM (Volt-Ohm Meter) for under $25 from most auto parts stores, Home Depot, etc. Just make sure it's got a 20V or 25V scale so you can readily tell the difference between 14.3 volts and 15.2 volts.

Hang in there!

All the best,
Mark
 

·
Registered
Joined
·
3 Posts
So I’ve recently experienced the same thing with my 17 Focus ST. When I cold start the car, rpms are fine. Drive the car and everything is great. But once you shut the car off and warm start the vehicle. The rpms suddenly drop really low almost about to stall then the engine shutters. The rpms spike back up and is around normal idle rpm range. What I did realize about this is every time I get a new oil change it stops doing it for a bit. Once the oil gets ran through the motor a few times it starts back up again... still doing some research to fine out what it is exactly.
 
1 - 12 of 12 Posts
Top