Hello,

Looking for some Ecoboost advice if possible please, whislt I am a very compentant home mechanic, struggling to get my 2015 Focus, 1.0 Ecoboost back to running properly,

It's a bit of a long story:

At the start of October, the car went in for it's wet belt to be replaced at 114,000 miles and 10 years old. The car went into the garage in perfect running condition, with no issues.

Sadly I picked a very poor garage, that I am still considering legal action against, but here is the status of my car after it left them with it's new wet belt:

Cylinder 1 fuel injector seal leaking

Exhaust loose and blowing heavily at the connection to the downpipe / cat

Turbo inlet pipe incorrectly connected and folded in on itself

Missing O ring on the turbo oulet elbow, boost leaking

Damaged injector connector

As you can imagine the car drove terribly,

After fixing all of the obvious above issues, as well as:

New upstream O2 sensor

Refurbished injectors

New Spark Plugs 

Smoke test of the intake & exhaust system, as well as the vacum system controlling the turbo (No leaks)

I am still facing major engine issues.

Under high load, the engine heavily cuts power, in a jerky and jolty fashion, the cuts are very on / off, oscilating and jolting down the road

When driven steady under lighter load, the vehicle runs smoothly and pulls well, through the entire engine speed range, with no issue, but if I venture over ~70% throttle, it starts heavily cutting power, both at low and higher engine speeds.

I have been having an intermittent catalyst efficiency MIL light, but no other fault codes. Last week the car failed it's MOT due to emissions, CO output very high, but all other readings, very good. The car was heavily smoking, white smoke, turning darker under continued load. I don't believe the car is using coolant, with the level staying steady.

I am aware the catalyst has failed, and needs replacing. I suspect the poor engine running has burnt it out. But what I want to avoid is fitting a new cat, and burning that one out too.

Any thoughts on what I can check on the 1.0 Ecoboost, that may be causing my jolting power cuts under load?

I have Forscan software, and have looked at a lot of data. I am struggling to see much wrong.

Fuel pressure is good, variable valve timing is spot on, boost pressure follows the desired profile, when it cuts power, the engine goes lean, I think that is a result of the fuel cut, rather than the cause of the fuel cut. No faults or missfires flagged.

Could a failing blocked burnt out catalyst be causing these running issues? Or likely another cause, that has burnt out the cat?

Many thanks for any advice on this, really at a loss now, outside of a catalyst repalcement and seeing how it drives,

Thank you

 

Hi, 

 

Ive done numerous wet belts on these engines across the ford range.

 

The pipework comes off complete and should have all seals still attached. and unless they were throwing the pipes onto the floor they shouldnt come away. 

 

the cat is usually removed at the manifold, then the flexi section (most often always splits or is burst anyways) so is also replaced as part of the job. 

 

it sounds like the car is/has been running rich. which would indicate a faulty or improperly plugged in sensor. as you no doubt know the cat is probably damaged beyond repair. 

 

As a temp measure, take out the top o2 sensor and take the car for a quick run, putting it under load. if the car drives ok, that will confirm the blocked cat.  if still the same, the issue lies elsewhere. 

did they take the sump off and do the oil pump belt? if not, then they wont have cleaned the oil strainer. 

 

they should have provided a detailed invoice stating eexactly what was done, but the overall cost would also be an indicator, if anything less than £1200 they took the shortcut 

 

Ultimately a detailed scan using forscan for codes is needed and posted on here. 

 

Cheers

 

Ste

 

 

Many thanks for the info Ste, 

So yes, the sump was removed at the garage, and the oil strainer was cleaned, it was completley covered in bits of rubber belt, and the old belt was very worn. I had photos / videos of this from the garage whilst the work was carried out, and at this point felt a good job was being done.

My suspicions have always been around something hasn't quite been re-fitted or plugged back in properly after replacing the belt, considering how much was left in a bad state around the top of the engine.

I shall have a go running very briefly with the upstream O2 sensor removed, and see if it is improved under load, I assume this is to allow any exhaust back pressure due to a blocked cat to escape?

The forscan data I have looked at seems to show the engine goes lean, rather than rich. During the MOT test last week, the fast idle emissions test showed 1.017 Lambda, so slightly on the lean side, but within limits, and HC output of just 62 ppm, so from this, it would appear the engine is burning well. CO output was up to 1.01%, way over the 0.2% allowed, and I suspect this is down to the ruined Catalyst not converting it to CO2 as it should be.

Is there a way in forscan to run a more detailed scan for codes? I have used it to check for DTC's, and nothing is usually present, just occasional Catalyst efficiency faults. But if there is a way to run a scan in more detail, happy to run this and share on the thread here,

Many thanks,

Regards,

Luke

3 hours ago, Luke Wakelen said:

Is there a way in forscan to run a more detailed scan for codes? I have used it to check for DTC's, and nothing is usually present, just occasional Catalyst efficiency faults. But if there is a way to run a scan in more detail, happy to run this and share on the thread here,

Have you tried a Mode 6 Test in FORScan, or a Key on Engine Running Test?.

The results will just be a series of numbers that don't mean much but there may be some pointers.

A bit of a long shot, but try Live Monitoring the Accelerator Pedal Position with FORScan to see what is happening, it should follow what your right foot is doing whereas the Throttle will do what the PCM tells it to do based on the Accelerator position and a lot of other things.  

Maf sensor readings on live data wiukd also be helpful. 

 

I cant think of anything that would give your issues simply by changing the belt,  even if all the cables were not clipped into their relative places, as long as all sensors are connected and functioning, the car should run fine. 

 

Out of interest can you send a pic of the top of the engine to see what state they left it in?

Il have a compare to the focus I have sat here waiting for a belt after Xmas. 

 

There is a possibility they dropped the cat, or even worse swapped it out with another one hoping to use yours in someone else's car. (John wayne garages everywhere).

If it can proved its down to negligence, and the garage is a registered business, you may be able to go to trading standards. 

Did you get an invoice? And how did you pay?

 

Cheers

 

Ste

 

 

Many thanks both,

I am currently away for Christmas and New Year, back with the car on the 4th Jan. Merry Christmas by the way!

Once back with the car, I shall run the mode 6 and engine running test with Forscan, and share the results here, as well as some more live monitoring of the throttle pedal and throttle position, and some photos of the top of the engine.

I did suspect a Maf sensor when the issues started occuring, but then discovered the ecoboost in my Focus doesn't use a Maf sensor, just two MAP sensors, one pre throttle, and one post throttle, I have looked at data from both the MAP sensors, and they appear to give sensible readings, and follow what I would expect to see.

Funny you should mention swapping parts out, when I had the injectors tested, all 3 failed for spray pattern, and were in a bad way. Now they may have simply gone bad over their 10 years of life, but I had zero running issues before it went into the garage, to then have a poor running engine and 3 bad injectors seemed suspicious. But now with 3 good injectors fitted, the issue remains unchanged, with no real improvement noticable. 

I have a very basic invoice from them, that lists changing the timing belt, but does not go into detail. I paid part cash, part card.

I have below some Forscan live data , the most recent I have from the car, this was before I had the injectors tested, and made good, but a lot of the other issues resolved, boost leaks etc.

Here are the two MAP sensors, pre throttle in Orange, post throttle in blue, seem to provide sensible readings

In the data, looking at 400 seconds onwards, is a section where the fauilt occurs under load:

Blue is pedal demand, holding at 100%, engine speed is very jolty in orange, does not pick up or pull smoothly, delivered lambda ratio tends towards 20, running lean. 

Looks like I have in the data set both pedal positon, and throttle position:

At the region after 400 seconds, the throttle is not opening beyond 60%, whilst the pedal input is demanding more, 100%. I guess it is hard to know if this limit on the physical throttle, is an error in the throttle body, or due to the car responding to an issue elsewhere. Any logical checks to make on the throttle body?

Interestingly, if I keep my pedal demand below ~60%, the car drives fine, but if I go above ~60%, the throttle doesn't open anymore, and the car starts running badly, very odd that Lamda tends lean rather than rich, as less air should tend towards a rich state?

I am not able to attach the excel file here, doesn't appear to be an accepted media type, but please let me know if I can share graphs of any other signals which may be of interest,

Many thanks

Regards,

Luke

4 hours ago, Luke Wakelen said:

or due to the car responding to an issue elsewhere.

I think that is likely. The data you have posted looks fine and if there was a defect in the Throttle Body I would expect a fault code.

So the car runs fine up to 60% throttle demand and the manifold pressure is sensible, the plugs all spark when they should.

You have fuel starvation.

Start checking fuel pressures.

Fuel pressures was something I looked at very early on,

Forscan live data shows the fuel rail pressure closley followed desired fuel pressure, as does the low pressure fuel side. Low pressure is graphed against the right hand axis so it's easier to see. So I took from this fuel delivery and rail pressure looks good?

If I zoom into the 400 seconds region where the poor running occurs under high throttle input, there are small deviations in rail pressure, but I wouldn't have thought this would be enough to cause poor running? Still sitting at over 14,000kpa when under load.

 

Question, do the 1.0 ecoboost injectors need coding to the ECU? I couldn't find anywhere in Forscan a maintenance option to code them, so assumed this wasn't required? Only two of my original injectors cleaned up sufficiently to give a good spray pattern, so I have fitted one new injector, and couldn't find anywhere to code the new one in.

Many thanks,

Regards,

Luke

I suspect that they might well need coding. Unofix is usually clued up on this but that sounds like something that needs checking. Small deviations in rail pressure could indicate that an injector is overfuelling on one cylinder and starving the other two of course as the rail pressure should remain constant less the squirt of fuel which will not reduce the pressure much, because the system is designed that way.

8 hours ago, anon said:

I suspect that they might well need coding. Unofix is usually clued up on this

The injector expert is @Tizer.

Have the previous 'learnt' values been reset ?

I don't know if the Injectors need coding on that Engine or not. If everything including all the Injectors are working as they should then the PCM will gradually Adapt if new Injectors have been installed.

Usually if there is a problem it will show as a rough Idle, which doesn't seem to be the case here.

Many thanks all,

Previous learnt values have not been reset yet. I did see a Forscan maintenance operation that was along the lines of PCM reset.

Will running this function clear the old learnt values? After a good google search, it would seem the 1.0 Ecoboost injectors don't need coding, but there is discussion around an ECU reset may be needed to re-learn the new values.

Many thanks,

As the engine has had extensive work and new electronic parts, it is most unlikely to do any harm. I would go ahead and see what changes.

I would be looking at the O2 readings to see what happens at the point where the engine starts playing up.

Just  wondering, will it make full revs cleanly from idle when not under load? If so, that would rule out the ignition system pretty definitively which points back to fuel.

(I would by now have double checked the belt timing and whether or not the variable cam timing hasn''t been buggered up by the garage.)

Sure, I'll give that a go once back with the car and run the reset.

Regarding O2 readings, the Lamda goes lean when the engine starts playing up, I am not sure though if this is the cause of the power cuts, or a result of the ECU cutting fuel for another reason.

I have checked the variable valve data in Forscan, and the variable timing follows the desired values spot on, so I don't think there is a variable timing issue:

And yes, the engine revs freely under no load, even keeping the throttle below ~60%, it will run all the way to the red line under load without missing a beat, just doesn't like high throttle inputs.

To me, this also ruled out the timing being off, but I can check the belt timing, is there a relatively easy way to check the timing on the Ecoboost, without removing lots of parts?

Many thanks

Hi all,

I am now back with the car, and have just run the ignition, and engine running PCM self tests, neither of these appear to have highlighted much:

Ignition on, engine off test DTC:

Engine running test DTC:

 

I now have a new Catalyst for the car, and will get this fitted in the week, once our snow has melted.

I will then run the PCM reset, and go for a good drive to put the first heat cycle through the Cat and see how I get on.

Many thanks, regards,

Luke

 

I don't think that will be a good idea until you get to the bottom of the temperature sensor problem.

I was confused by the temperature sensor problem reported on the ignition only self test, the temperature sensor reads fine, when I measure with Forscan, coolant temp is there and showing values I would expect to see without issue

So no reason based on that to suspect a temperature sensor problem?

Did you have a look at the Mode 6 Test?

Ok, my mistake. If the engine is cold then the temperature will be out of range. Temperature sensors are vital to mixture control and any rough running investigation regards them with suspicion if an air leak can't be proved.

On 1/4/2026 at 10:25 PM, Tizer said:

Did you have a look at the Mode 6 Test?

I did yes, I ran both an ignition only test, and engine running test, both results above

So with a new Cat fitted, the car aced it's emissions test this week, was really low and passed with flying colors. 

The car is driving better, the best it has been since it came out of the garage following the wet belt replacement, but is still not 100%, still exhibiting cuts in power at high throttle inputs. If I drive in a steady and relaxed manner, it runs and behaves faultlessly.

The cuts in power at high throttle inputs do appear to get worse once the engine has warmed up, so I think this weekend I will try a smoke test on the intake once everything is hot and at operating temperature, I wonder if something has cracked, but only opens up when warm.

Still no faults or MIL lights to give any indication of what is wrong, and all of the live data I look at, highlights everything appears to be working as expected.

Many thanks for any further thoughts, I am wondering if my next best option is an engine dyno diagnostic on the car, with someone plugged in who can see a lot more than I can with Forscan. I am also considering as the car is worth not a lot now, just keep driving it steady as my daily driver, which should avoid ever seeing the fault, far from ideal, but its a 10 year old ecoboost with 116,000 miles on the clock, so not worth pouring much more money into it