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Premium Member
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Discussion Starter · #1 ·
Hi

Driving the RS today and half a mile into the journey revs were irratic while idling at traffic lights. Went to set off, no power and then cut out. Engine malfunction on the dash. Restarted and got it home with noticeable lack of power and few cut outs but each time it restarted with no warning. It was just once it had got running.

Got home plugged it into a cheap code reader I had and got codes P2101 P2108. But only when engine malfunction had cut the engine. Once restarted code disappeared.

Bit of background I recently got second hand cais and fitted it. So I put the airbox and filter back on but no change.

Now I have searched the codes and symptoms on the forum and it is leading me down two most likely cause being either MAF or the throttle body unit as this includes the throttle position sensor.

I have a friend who has better software coming tomorrow to check what codes he can get off the car. But just wondered if anyone had the same issues and any insight into whether it is easier to diagnose on over the other of the above 2 potential issues or if I am looking at it completely wrong?

Thanks.
 

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812 Posts
Give the maf a clean with contact cleaner or worst case if you have to buy one then get it from opie oils as they're much cheaper than any tuner using discount code Focusrsoc
It's most likely just a bit dirty
 

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BMW 1M
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10,833 Posts
Is your battery healthy and fully charged?

It may be worth putting it on charge overnight if you can before your mate checks again tomorrow. Those codes should still be stored under 'pending'.

I've had a quick look and those codes have previously been associated with battery or ECU issues.
 

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Discussion Starter · #5 ·
Right guys. So couldn't find any codes on software. It oddly gives engine malfunction but once restarted disappear and even on his software would not show pending?

So I changes maf sensor for new part. No better.

Next changed throttle body, again secondhand due to cost but no change.

So I tried map sensor again new. No change.

Next I tried looking for leaks. Couldn't find anything that stood out.

Next I charged battery. Once charged I realised my battery charger also did alternator and battery test. Showed good battery, good alternator on running but bad on running under load.

So potential could be alternator but would it really cause engine to pulse at tick over like it is struggling for fuel or air?

Also I have noticed that when you get in the car and switch in but do not start engine when the fuel pump primes it does bursts not one continuous? Unsure if it has always done this as never paid attention before.

So now I am between alternator or fuel pump or potentially both? With cost am thinking that alternator would be better start and is showing bad on load test but really struggling to understand that how that would cause the idling issue but have read these electrical gremlins throw up some strange issues.

Thanks.
 

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3,301 Posts
I would say getting a local garage to leak check the boost system. Small air leaks can cause big issues and you shouldn't be charged too much. Its what I had on my mk2. Essentially if you have a boost leak the engine measures the air entering the engine and measures the fuel accordingly
If you loose some air it between maf and engine it really confuses the ecu. But as above I would be sure before throwing more parts at it. What's £100 in diagnosis and then fit the right part vs keep on buying stuff that doesn't fix it?
 

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Just an update. Got the car towed to a local garage that knows RS'S bit of luck he pulled a fuse to check and saw corrosion. Pulled all the other fuses all corroded.

Cleaned up fuses and terminals and all running good now. Seems some ingress into the fuse box somehow? Unsure if someone has pressure washed the engine at some point?

Then on the way home undertray decided it did not want to be on the car anymore. If its not one thing it's another.
 

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Discussion Starter · #10 ·
Oddly enough many years ago my ST170 went through a rough patch which resulted in diagnostics/sensors and fuel pump to name a few bits and it has just popped up on my Facebook timeline as was this time of year a decade ago. So obviously from next year I will just take the RS off the road for March and April 😂.
 

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2009 mk2 Ford Focus RS
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2,563 Posts
I have had a similar problem with my car now. :(
Around 3 weeks ago, one morning went for a 15 min drive, then parked up for 30 mins. Came back out to start the car then I get the Engine Malfunction on dash, buzzer, warning lights and red triangle. Driving like this was weird as it was reduced power, very delayed throttle response and hard steering. Switched engine off and restarted, everything went back to normal.
Then yesterday the dreaded problem came back. Seems to happen everytime I go over this bumpy surface road near me. This time it now happened when I was driving the car around 5 mins after switch on. Eventually drove for 2 mins like this before I switched the car off. Car was ok after this. Then later again yesterday evening I got the same problem, around 5 mins after switch on, although i did not go over the bumpy surface road, another route with one speed hump. I switched car off after 1 minute then restarted and it was ok.

I am also wondering if it is the ECU or fuses with corrosion as someone had put it.

My battery is charged, I put a standard fault code reader on (the bluefin one) and got no codes. If I get a chance today or tomorrow I would check over the car to see if anything has got loose. I would be gutted if the ECU has gone.
 

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Premium Member
2009 mk2 Ford Focus RS
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2,563 Posts
Checked over my earths I could not find anything. Was doing a voltage test and noticed that when I had the heated screens on with engine running it dropped to 12 volts. Before I started the car I think battery was 12.11 volts.
I took the battery off to charge, and put it back on this evening, so far I have not had the fault come up.
I am wondering if the fault came up the first time as I was not driving it much and think I left it nearly a month without starting the car.
 

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1,163 Posts
I had a similar problem with one of my Cosworth Sapphire's so I took it to my local tyre depot and they did a battery drop test and found it to be an intermittant short in one of the cells, had a new battery fitted and that sorted the problem.
 

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Premium Member
2009 mk2 Ford Focus RS
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2,563 Posts
It was ok for a good 3 days, then it has come back again. It is now starting to get worse now. Seems to show power steering malfunction then the engine malfunction. Seems to happen when the car has warmed up, around 15 mins of driving. Once it took ages to clear, and another when the engine was switched off and switched back on, the fault did not clear and came back on with the malfunction warning. It now makes the other displays show with a ----- line where it did not previously do this.
I do not know if it is related, but the car now has a high smell of fuel.

I am waiting for some forscan lead in the post, should have came on the 7th, irritating, but I guess royal mail is slow down to covid

 

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Premium Member
2009 mk2 Ford Focus RS
Joined
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2,563 Posts
It was ok for a good 3 days, then it has come back again. It is now starting to get worse now. Seems to show power steering malfunction then the engine malfunction. Seems to happen when the car has warmed up, around 15 mins of driving. Once it took ages to clear, and another when the engine was switched off and switched back on, the fault did not clear and came back on with the malfunction warning. It now makes the other displays show with a ----- line where it did not previously do this.
I do not know if it is related, but the car now has a high smell of fuel.

I am waiting for some forscan lead in the post, should have came on the 7th, irritating, but I guess royal mail is slow down to covid

Now I have forscan, I have continued my own thread at
 
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