P0172 & P0175

[mcweasel01]

Hi, wondered if anyone could give me any suggestions

 

2011 1.6 Petrol C-Max keeps intermittently throwing P0172 & P0175 faults.

Replaced Lambda sensors, MAF & spark plugs but still keeps coming back (actually getting worse now). 

When setting off from junctions/roundabouts, it just doesn't move (foot to floor, revs stay around 800), have to drop clutch & accelerator to get revs to 1500-2000 for it to pick up & go. 

When idling it has a slight shake (either just before EML or when EML light on) & it's started to feel like it's revving slightly despite foot not being on accelerator & rev counter not moving (stays around 800)

I've taken it for diagnostic, and didn't really get anywhere with that independent garage.

Anyone have any suggestions? Not sure if cat going/gone, fuel pump going/gone, fuel injectors failing

Thanks

[mcweasel01]

I've had another mechanic plug in, and he found 86000 misfires 🥴

First thought was the Lamba sensors were bad (despite being replaced) but they tested fine. 

Long Term & Short term fuel trims were waaay out of whack, I don't have the info but think long term was -30 & short term -8

It's now booked in with Ford to see if there's an update it needs, but any suggestions at all are appreciated 

[mcweasel01]

Well, had it in a Ford garage twice and all they could tell me was a regurgitation of what I told them. As the EML is intermittent, and it's been off when it goes in, they apparently can't do anything. Only suggestion they gave is replace spark plugs (done Aug20 & June22) & air filter (Feb22)

I do have a full list of what it does when the EML is about to come on, but now thinking it could be the Throttle Position Sensor

 

As always, anyone have any suggestions, please let me know

 

 

 

[unofix]

Hi Kevin, I would recommend you get FORScan and read the codes while the EML is on.

There are a few versions available and I normally recommend the one for use on a laptop which has the full programming capability. In your case I suggest the mobile app for your phone so that you can read the DTC's as soon as the EML comes on.     https://forscan.org/home.html

This video may also help give some pointers to the causes of the two codes that you have.

 

[mcweasel01]

Thank you! I'll look into the ones suggested in the video and get the mobile app for forscan, do I just need a bluetooth odb cable? 

I think we've got an ancient laptop laying around somewhere too, see if it'll actually turn on & try that

[unofix]

These two are specially made for use with FORScan and are recommended by them.

Laptop cable. 'vLinker FS' : https://www.cartool.co.uk/wholesale/elm327-for-ford-mazda.html?gclid=Cj0KCQjwvZCZBhCiARIsAPXbajtYdFpSHxAntTryvmsqsBGQXxlJn5m97_R1rOhYfFA9xiGHCaSkkhUaAmAEEALw_wcB

bluetooth OBDII adapter : https://www.amazon.com/dp/B08FSXYXLG

[mcweasel01]

Was just coming back to ask for cable recommendations! 

[mcweasel01]

In the voice of Professor Farnsworth: 'Good News'...

I have a cable, and I have Forscan. And I've plugged it into my car. Now, I'll be the first to admit it was daunting & exciting and I don't have a clue what I'm doing (wife was reluctant to let me loose in case I somehow break the car)

Anyway, I've run the Fuel Trims & I'm getting:

Long Term circa -12.5

Short Term between 3.91 to 10.40

I have no idea if this is good or not, or other checks I should do?

The EML isn't on at this point, so the above may be pointless but somewhere to start

[Tizer]

Regarding the misfires, if you have a look in Mode 6 in FORScan Tests there may be individual misfire counters for each cylinder.

Whether it is only one cylinder that has the problem or all of them it may help narrow down the problem.

[mcweasel01]

Just now, Tizer said:

Regarding the misfires, if you have a look in Mode 6 in FORScan Tests there may be individual misfire counters for each cylinder.

Whether it is only one cylinder that has the problem or all of them it may help narrow down the problem.

Thanks, I'll take a look at that tomorrow & see what I can find

[mcweasel01]

Hopefully this will upload. It's what I have on the Mode 6 test. 

I was only able to get to the misfires via the live data with engine running. I couod see cumulative 86,000 misfires, but when I checked the cylinders, they were all showing 0. Whether they've been cleared previously or not, I don't know

[Tizer]

It's a shame that your engine is not well catered for in FORScan's Mode 6 tests, some older ones are not.

it maybe that the misfires only occur when the car runs rich or it is a red herring, sometimes when a PID in FORScan is not implemented for a particular engine then a default value is given, which is meaningless. I would have expected a Fault Code to be registered if there was a Misfire problem.

If you continue to drive without the problem occurring then the Long Term Fuel Trim will probably drop until the problem occurs again. 12.5 is on the high side of not that bad but not high enough to trigger a fault, from memory plus or minus 25 is the trigger point. 

I don't know what is causing the fault codes that you are getting. 

[mcweasel01]

Thanks @Tizer I'll keep plugging it in over the next few weeks. At the moment it's actually behaving, which is the longest run its had in a while without causing me a headache. I have no doubt the issue will be back, at least now I have the capability to scan it, and somewhere to give the results to for advice 

[mcweasel01]

Well, wanted to give an update after a month or so and it's done that thing where you get the equipment to find the fault... And the fault doesn't reappear!

For this year, this has been the longest without the issue, however as I was having the timing belt & water pump done I figured I may as well change the throttle position sensor (picked up new from an auction site for £400 less than ford garage quoted!)

I do need to check the fuel trims, see if they've improved, but if anyone is after a throttle position sensor, drop me a message and you can have my old one!

[mcweasel01]

It's been the best 6 months of this ownership, but alas, EML has returned! 😭

 

Plugged in & read the codes, and surprise surprise, P0172...

Anyone able to give any pointers before I end up going out & buying a new engine? 

[rd457]

A quick google search for the code turns up the following suggested causes:

• A dirty mass air flow sensor overstating the amount of air entering the engine which may cause excessive fuel delivery
• A bad oxygen sensor
• A leaking fuel injector allowing too much fuel to enter the combustion chamber
• A faulty fuel regulator, which may not be regulating the pressure of the going to the engine as it should
• A vacuum leak
• A possible fault in the coolant system such as a stuck thermostat or bad coolant temperature sensor
• Worn spark plugs

I see that you've changed several items on the list, but there are other possibilities here that you don't seem to have mentioned having been looked at, like the fuel pressure regulator.