Rough start idle

[Gavin1274]

Hello everyone,

my wife’s car is a 2015 eco boost ford fusion SE. a few weeks ago on starting the car it will idle pretty rough for a few seconds then be totally normal and drives normal. Usually the rough idle is after we have been driving and car has sat for 10 minutes or so and go to start again. But sometimes on cold start too. A few months ago I replaced the spark plugs and ignition coil(only on cylinder 3) and it ran great, until these on start misfires started. Today the check engine light came on and I checked it at auto zone and it said misfire on cylinder 3. 
 

I took the hose that goes into the throttle body off and I did notice some oil in the hose and the hose had build up on the outside, but after looking it up it seems some people said that’s normal. 

Thank you all in advance.

[WKelley]

If it is higher mileage, 100K or more, I'd do a quick compression test.  Inspect wiring to coil and injector as well.  Swap that coil to another cylinder and see if it follows.  If it was a cheapo coil it is a likely suspect.  Try all the easier things first as the ecoboost engines are known for head gasket issues. 

[Gavin1274]

13 minutes ago, WKelley said:

If it is higher mileage, 100K or more, I'd do a quick compression test.  Inspect wiring to coil and injector as well.  Swap that coil to another cylinder and see if it follows.  If it was a cheapo coil it is a likely suspect.  Try all the easier things first as the ecoboost engines are known for head gasket issues. 

it currently has 171k on it. I will be swapping the coil since it is still under warranty. Would a bad coil cause only the rough idle/misfire upon starting it? And it is only sometimes 

[andyross]

Could even be a leaky injector causing a cylinder to get flooded while off.

[Gavin1274]

1 hour ago, andyross said:

Could even be a leaky injector causing a cylinder to get flooded while off.

Would there be an engine code for that if it was the case? 

[bbf2530]

39 minutes ago, Gavin1274 said:

Would there be an engine code for that if it was the case? 

 

Hi Gavin. In the majority of cases, DTC codes do not pinpoint an exact cause. They merely point the tech  in the right direction and then there is a troubleshooting tree to follow in order to find and correct the actual cause.

So there can be and usually are a multitude of causes for any particular DTC code.

For example...In your case, an engine misfire could be caused by a bad spark plug, faulty injector, bad coil, bad wire, a failing PCM, etc. etc.

 

If you know the code, then Google it and you will be able to find the troubleshooting tree. Or post it here and someone can do the same.

 

Let us know how you make out and good luck.

Edited October 30, 2023 by bbf2530

[drolds1]

At this mileage, carbon buildup on the valves can cause this condition as well.  It's a common issue with GDI engines.

[Gavin1274]

6 hours ago, drolds1 said:

At this mileage, carbon buildup on the valves can cause this condition as well.  It's a common issue with GDI engines.

Is there a good way to tell if this is the case? And what can I do to clean them ? Thank you 

[drolds1]

Based on what we've learned over the years, it's a fair assumption in your case.  Still, a visual inspection is necessary to confirm.  The intake manifold needs to be removed in order to see the valves.  This also enables access for cleaning.  For years, Ford did not approve any method for removing carbon deposits on the intake valves.  Spaying solvents into the intake of a running EB engine could cause chunks of carbon to be drawn into the engine and damaging the turbocharger(s).  See this video for a demo of manual cleaning.  Ford Tech Makuloco is the guru of all things Ford around here and elsewhere on the web.  Here's an updated video demonstrating 2 newer, approved mechanical methods.

[Gavin1274]

1 hour ago, drolds1 said:

Based on what we've learned over the years, it's a fair assumption in your case.  Still, a visual inspection is necessary to confirm.  The intake manifold needs to be removed in order to see the valves.  This also enables access for cleaning.  For years, Ford did not approve any method for removing carbon deposits on the intake valves.  Spaying solvents into the intake of a running EB engine could cause chunks of carbon to be drawn into the engine and damaging the turbocharger(s).  See this video for a demo of manual cleaning.  Ford Tech Makuloco is the guru of all things Ford around here and elsewhere on the web.  Here's an updated video demonstrating 2 newer, approved mechanical methods.

Thank you for your reply. Have you ever seen people use seafoam? After doing little research it seems effective and someone said they reached out to seafoam themselves and were told it dissolves the carbon so there is no chunks that would harm the turbo. Have you heard that? 

[bbf2530]

3 minutes ago, Gavin1274 said:

Thank you for your reply. Have you ever seen people use seafoam? After doing little research it seems effective and someone said they reached out to seafoam themselves and were told it dissolves the carbon so there is no chunks that would harm the turbo. Have you heard that? 

 

Hi Gavin. Seafoam is among the intake tract cleaners/solvents that drolds1 mentioned are not approved for used by Ford, contrary to whatever the Seafoam rep/reps may have told you. This information is explained in the Owner Warranty Guide for our vehicles.

 

The only method of cleaning that Ford approves for the EcoBoost TDI (Turbo Direct Injection) engines is removing the intake manifold and manually cleaning the valves/seats etc. via walnut blasting or other similar methods. No intake tract cleaners/solvents are approved, since they can all result in possible damage to the turbos, turbo seals etc. 

 

Also, without proper diagnosis, I would not be so quick to assume what the issue may or may not be. It may be better to get the help of a shop or tech you trust to help correctly diagnose this problem before you perform any self-help that may make things worse or simply waste money.

 

Let us know how you make out and good luck.