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Discussion Starter · #22 ·
Ok guys. I've replaced the Fuel Rail Pressure sensor. For anyone in the UK, this has a different part number here. It's 5 255 376 in the UK. So far so good. I think it may have solved it, but I wasn't in stop start traffic to really extensively try and induce the hunting idle fault.

@Crevarius FYI in case you get someone else British asking you about this part number.

Will go a cruise tomorrow and report back. Hopefully my issue is resolved, but I know what my luck is like!

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Discussion Starter · #23 ·
Update - problem still occuring :(

Seems to be at ambient temperatures lower than 3-4C, it doesn't do it. But it was 6C today and it done it. Just started up at the petrol station and bomb, surged from 800 down to 500 twice in a row then settled in at 800. Argh! What to try now :(
 

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Update - problem still occuring :(

Seems to be at ambient temperatures lower than 3-4C, it doesn't do it. But it was 6C today and it done it. Just started up at the petrol station and bomb, surged from 800 down to 500 twice in a row then settled in at 800. Argh! What to try now :(
Did it happen after filling up you car with fuel?

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Ford Focus cars ALL have evap. issues. If you want to find out if you have a bad purge valve, leave it run while you fill it with gas. If it misses or stumbles, it is the evap. purge valve. Easy to fix and @ $65. My ST would die when I got gas, it was so bad, but when I brought it in for the recall, it passed! It also gave me massive idle misfires. The dealer had replaced my plugs, coils, injectors, head and finally the engine and it still misfired. I replaced the evap. purge line and it quit.
 

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Discussion Starter · #26 · (Edited)
Did it happen after filling up you car with fuel?

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Update guys:

Annoyingly, still no fault codes, except a random miss
fire at 60mph sometime ago, only viewable on diagnostic tool. No warning lights on or anything though on though.

I've been living with it for a while, but I finally got annoyed enough to take it to an independent garage instead of Ford. Went for a drive with IDS/Forscan data logging. During idle, the short term fuel trim (STFT) dips when the idle issue occurs then jumps up again. Additionally, if anyone is still under warranty with ford, the best way to trigger the issue in front of them is to drive pretty hard, and then stop and let it idle. It'll almost always do the issue on demand after driving hard (just do 2-3 30-60MPH pulls).

Something else we noticed too: when going full throttle in third and fourth gear. Data logger showed fuel pressure actual as being about 3/4 what fuel pressure demand was. Perhaps this is down to the same issue?

Route we are going down now is to replace the low pressure fuel pump (LPFP) - pain, as tank needs to be dropped from below, so lots of bits in the way.

Will report back if this fixes it, fingers crossed though and feeling good about it!
 

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Discussion Starter · #27 ·
Update guys:

Annoyingly, still no fault codes, except a random miss
fire at 60mph sometime ago, only viewable on diagnostic tool. No warning lights on or anything though on though.

I've been living with it for a while, but I finally got annoyed enough to take it to an independent garage instead of Ford. Went for a drive with IDS/Forscan data logging. During idle, the short term fuel trim (STFT) dips when the idle issue occurs then jumps up again. Additionally, if anyone is still under warranty with ford, the best way to trigger the issue in front of them is to drive pretty hard, and then stop and let it idle. It'll almost always do the issue on demand after driving hard (just do 2-3 30-60MPH pulls).

Something else we noticed too: when going full throttle in third and fourth gear. Data logger showed fuel pressure actual as being about 3/4 what fuel pressure demand was. Perhaps this is down to the same issue?

Route we are going down now is to replace the low pressure fuel pump (LPFP) - pain, as tank needs to be dropped from below, so lots of bits in the way.

Will report back if this fixes it, fingers crossed though and feeling good about it!

Update, not done the LPFP yet - a lot of work to get to it - instead done the fuel filter as it looked poorly. Didn't solve the problem, but get more pops and bangs now as a result somehow - good result in my book though 😁

Going to knock out the fuel rail pressure sensor and front O2 sensor next as a precaution, as it's far cheaper to do than do the LPFP.

Does anyone any suggestions on what could be causing the fuel pressure issue, apart from the low or high pressure fuel pumps? Is it possible I have something grounding somewhere, which is causing random the spikes in long/short term fuel trims at idle? Or will it indeed be something mechanical?
 

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The FRP is the easiest to replace and a likely cause since it's actually measuring pressure. My issues required a new front o2 sensor, FRP and evap purge valve to resolve fully.

Something else we noticed too: when going full throttle in third and fourth gear. Data logger showed fuel pressure actual as being about 3/4 what fuel pressure demand was. Perhaps this is down to the same issue?
What values was it showing? My tuner said FRP Actual should never drop below 1400psi during WOT runs, and all of my runs show FRP Actual above 2800psi by redline.

I believe it's a good idea to at least check your Big 3 after driving the car for a few years, especially if it has seen snow or salt. So many systems in modern cars rely on clean electricity to function properly. Blah, that's a whole other discussion anyway. :D
 

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Discussion Starter · #29 ·
The FRP is the easiest to replace and a likely cause since it's actually measuring pressure. My issues required a new front o2 sensor, FRP and evap purge valve to resolve fully.



What values was it showing? My tuner said FRP Actual should never drop below 1400psi during WOT runs, and all of my runs show FRP Actual above 2800psi by redline.

I believe it's a good idea to at least check your Big 3 after driving the car for a few years, especially if it has seen snow or salt. So many systems in modern cars rely on clean electricity to function properly. Blah, that's a whole other discussion anyway. :D
350440


Hmmm, the only thing left to try is the evap purge valve then I'm stuck again lol. Done the front O2 sensor and FRP sensor (second time for the FRP) yesterday. Interesting, the old O2 sensor had some white on it which would suggest I'm running lean.

Something else I notice also. If I drive with the A/C on and then come to a stop. It'll idle ok and it's likely to do the idle surge a couple times if I've just been driving hard. If I turn the A/C off, revs will sometimes shoot up to 1500 and hold there. It's like it still thinks the A/C is on and is sending the fuel needed to run it. Very weird. If you then turn the A/C back on, the regs drop back down then to normal idle. Another weird symptom that I only noticed yesterday.


Is there anywhere I can find a list of what the individual values should be or range of what they should be when looking at live data?
 

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Is there anywhere I can find a list of what the individual values should be or range of what they should be when looking at live data?
I think this is what you're looking for. Typical Diagnostic Reference Values
350444
 
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Discussion Starter · #31 ·
Update: looks like fuel pressure values before were a red herring. seems all ok now. replaced the evap purge valve today. a new issue has occurred though (before that was replaced, and is continuing after it too).

Car will randomly idle at 1500 revs now. I sat today parked up, and for 15 mins, the idle just sat at 1500 revs. happened again after replacing the purge valve too. this high rev idle seems to be worse on higher ambient temperature days. No fault codes.

I notice too sometimes, if i'm just in the car, and i drive off, once I go into second, if I let off once at about 16/17MPH, it feels like the throttle stays open for about 4-5 seconds after i let go, as the speed is maintained. then you feel it let go/start to die off/slow down as you'd expect it to do the second your foot comes off the accelerator.

throttle input when doing the 1500 rev idle is about 10%-11%, so normal for what you'd expect at idle - FORSCAN says desired revs were 750 at the time, but was getting 1500/1550.

do i have a dodgy throttle body I wonder? it's slightly sticking, but not enough to trigger a code? I guess that might explain the earlier issue too with the revs dropping at idle/unsteady idle at times (but not always)? Just obviously something is keeping the revs up, but no idea what.

Totally lost here, as I figured a dodgy throttle body would trigger a code.


Smoke tested the car earlier too, it passed fine, no air/vacuum leaks.
 

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Update: looks like fuel pressure values before were a red herring. seems all ok now. replaced the evap purge valve today. a new issue has occurred though (before that was replaced, and is continuing after it too).

Car will randomly idle at 1500 revs now. I sat today parked up, and for 15 mins, the idle just sat at 1500 revs. happened again after replacing the purge valve too. this high rev idle seems to be worse on higher ambient temperature days. No fault codes.

I notice too sometimes, if i'm just in the car, and i drive off, once I go into second, if I let off once at about 16/17MPH, it feels like the throttle stays open for about 4-5 seconds after i let go, as the speed is maintained. then you feel it let go/start to die off/slow down as you'd expect it to do the second your foot comes off the accelerator.

throttle input when doing the 1500 rev idle is about 10%-11%, so normal for what you'd expect at idle - FORSCAN says desired revs were 750 at the time, but was getting 1500/1550.

do i have a dodgy throttle body I wonder? it's slightly sticking, but not enough to trigger a code? I guess that might explain the earlier issue too with the revs dropping at idle/unsteady idle at times (but not always)? Just obviously something is keeping the revs up, but no idea what.

Totally lost here, as I figured a dodgy throttle body would trigger a code.

Smoke tested the car earlier too, it passed fine, no air/vacuum leaks.
Oh boy... I can feel your pain, this would stress me right out.

  1. Did you reset your keep alive memory(KAM) to clear your idle air trim learning? It's not required, but I do it any time I mess with something that could affect air trims. Clearing DTCs with a scan tool doesn't clear the KAM:
    351423
  2. Did you wind up replacing your battery?
  3. Did you check your grounds?
  4. Any codes being thrown right now? (especially P0505,P0506,P0507)
  5. What are the values for the following parameters at low idle speed?
    • Coolant temp
    • RPM
    • Load
    • Throttle position
    • Accelerator Pedal Position
    • Ambient temperature
  6. What are the values for the same parameters at high idle speed?
  7. Any patterns you can spot in any of the above?
 
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Discussion Starter · #33 · (Edited)
Oh boy... I can feel your pain, this would stress me right out.

  1. Did you reset your keep alive memory(KAM) to clear your idle air trim learning? It's not required, but I do it any time I mess with something that could affect air trims. Clearing DTCs with a scan tool doesn't clear the KAM:
    View attachment 351423
  2. Did you wind up replacing your battery?
  3. Did you check your grounds?
  4. Any codes being thrown right now? (especially P0505,P0506,P0507)
  5. What are the values for the following parameters at low idle speed?
    • Coolant temp
    • RPM
    • Load
    • Throttle position
    • Accelerator Pedal Position
    • Ambient temperature
  6. What are the values for the same parameters at high idle speed?
  7. Any patterns you can spot in any of the above?
U[USER24633]@Crevarius[/USER] I'll give this a try.

Can you recommend any data loggers? I can get access to IDS/VCM via a friend but unfortunately he's about an hour's drive away, so I kind of want to have an idea of the problem before I go back and harrass him again.

Can I out IDS on my own computer (if so, what do I need for it?), or would something like Carly give me access to those live data parameters?
 

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Could there be an intake leak after the MAP? I'm thinking that could keep the revs higher... kind of like the idle air bypass. And if you think your throttle body might be sticking, remove it and check it out. If it is gunked up from the pcv, then clean it up with some carb cleaner. If you do remove it, replace the throttle body gasket... just to be safe.

I also want to thank you for this thread. I also had the surging revs at idle a couple months ago, and the FRP fixed it for me. The really weird thing I noticed is that the rpm gauge would go up and down with the surges for a few seconds, then the needle would stop... even though the rpm's were still going up/down. I'd give it a little gas and the needle would move again. It's like Ford was trying to hide the surges from me.
 

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Discussion Starter · #35 ·
Could there be an intake leak after the MAP? I'm thinking that could keep the revs higher... kind of like the idle air bypass. And if you think your throttle body might be sticking, remove it and check it out. If it is gunked up from the pcv, then clean it up with some carb cleaner. If you do remove it, replace the throttle body gasket... just to be safe.

I also want to thank you for this thread. I also had the surging revs at idle a couple months ago, and the FRP fixed it for me. The really weird thing I noticed is that the rpm gauge would go up and down with the surges for a few seconds, then the needle would stop... even though the rpm's were still going up/down. I'd give it a little gas and the needle would move again. It's like Ford was trying to hide the surges from me.
I don't think I have any air leaks, as we did smoke test it and it passed with flying colours. We did take a look at the throttle body but didn't seem to be in bad condition. If there is something wrong with it, it's mechanical I think. Must just be a slight error or issue with idle position. Or it's in the way to seizing/sticking fully. Think only way to know is to replace it, but it's about £150. I want to find a way to check air and temp sensors before going down that road, as they're only £10/£20 a pop.

I went and bought a Carly OBD reader so hopefully I can get MAP and IAT sensor life data, see if anything funky is going on there.

Any other sensors anyone can think of would affect idle? I've got Crevarius' items noted down to monitor too.


And no worries- if this helps someone else too I'm glad. The issue is minor but extremely frustrating!
 

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U[USER24633]@Crevarius[/USER] I'll give this a try.

Can you recommend any data loggers? I can get access to IDS/VCM via a friend but unfortunately he's about an hour's drive away, so I kind of want to have an idea of the problem before I go back and harrass him again.

Can I out IDS on my own computer (if so, what do I need for it?), or would something like Carly give me access to those live data parameters?
I'm sure any quality bluetooth reader can do it. I use a OBDLink MX+ with Forscan, OBDLink EX with Forscan, and my AccessPort, but there are plenty of options out there.
 

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Hmmm.. notice the samething right after I feel up with fuel. Engine drops down in RPM almost likes its going to die. Interested too see what you figure out.
That's your evap purge valve. It's a known issue with our vehicles. Search for evap purge valve on here and you'll see.
 
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