I have fiesta 1.4 tdci 2010 with 160k miles

Starts and runs fine from cold (no smoke initially)

After 5 minutes of driving (as engine warms up):

White smoke begins from exhaust

Light at idle, heavy when revving around 2000 rpm

Radiator fan switches to full speed after ~5 minutes of running

Radiator fan turns off normally when engine is switched off (no after-run)

Fuel economy dropped significantly (from ~50 mpg to ~35 mpg)

No warning lights or fault codes present

Coolant temperature reading appears normal on scanner

Engine oil temperature shows –40°C, ChatGPT said my fiesta don’t have oil temp sensor and that’s why it’s -40

Heating works fine inside the car.

I have checked the coolant and it’s still above minimum.

there is no cream coffee colour in the oil cap or stick.

ChatGPT said might be early head gasket,

Visited a local machnic near by, he said he not expert in ford but said might be fuel filter or egr valve requires cleaning.

This whole thing started randomly couple of days ago, I was driving on 20-30 mph road and started seeing smoke coming from back of car and started hearing my radiator fan at full speed.

Can anyone recommend anything I can try at home to confirm what the issue is?

At a very basic level I'd keep a VERY close eye on coolant level.
If fan is running at full speed, it must be getting a logic or temperature related command so I'd also be looking at any Forscan (NOT basic OBD reader) codes and if none, checking live data for anything relevant, especially temperature.
Another option would be a relative compression test but you need a clamp meter etc for that.
Fuel filter likely unrelated - always change if it hasn't been done (I suggest 2 years for the replaceable cartridge type)
EGR again not my initial suspect at this stage UNLESS it has a leaking cooler which would allow coolant into induction tract (can the pipes be clamped or blocked to test that theory)?

Anyone?

Visible smoke, high speed fan and poor fuel economy all point to a DPF regen taking place.

Can you confirm whether yours has a DPF or not? I can't remember which year Mk7 started getting them.

My money is on turbo on the way out

1 hour ago, TomsFocus said:

Visible smoke, high speed fan and poor fuel economy all point to a DPF regen taking place.

Can you confirm whether yours has a DPF or not? I can't remember which year Mk7 started getting them.

It does have dpf

11 minutes ago, Hamid said:

It does have dpf

That's potentially a good sign. I suspect it's just continuously trying to regen. If you use Forscan, you can see distance since last regen, and number of failed regens, etc. Then check the DPF pressure readings as well.

If you don't have Forscan then check the pressure pipes from the DPF for any splits. And swap the pressure sensor with a good used one if any of your friends or family have a car with the same engine. Worst case scenario would be a blocked of cracked DPF. There isn't a vaporiser on this model.

1 hour ago, TomsFocus said:

That's potentially a good sign. I suspect it's just continuously trying to regen. If you use Forscan, you can see distance since last regen, and number of failed regens, etc. Then check the DPF pressure readings as well.

If you don't have Forscan then check the pressure pipes from the DPF for any splits. And swap the pressure sensor with a good used one if any of your friends or family have a car with the same engine. Worst case scenario would be a blocked of cracked DPF. There isn't a vaporiser on this model.

How long does it take for dpf to regen? I drove for 20 min and then left it running for another 40 mins. Do I need to keep it running for couple of hours?

14 minutes ago, Hamid said:

How long does it take for dpf to regen? I drove for 20 min and then left it running for another 40 mins. Do I need to keep it running for couple of hours?

Depends on engine temps, outdoor temps, driving speeds etc. But definitely not an hour. It should abort the regen after about half an hour max if it's not working.

Need to work out what's stopping it completing the regen if that is what's happening.

On 4/21/2026 at 12:15 PM, TomsFocus said:

Depends on engine temps, outdoor temps, driving speeds etc. But definitely not an hour. It should abort the regen after about half an hour max if it's not working.

Need to work out what's stopping it completing the regen if that is what's happening.

I done few more things, is this normal. When I rev at 2000 rpm, the coolant tank has two small pipes, the lower pipe is pushing some gas or air while the top pipe to the coolant tank is very hot. The coolant temp is 60 and radiator hose pipe is cold.

Could this be head gasket?

Link to video

Streamable

Watch unnamed | Streamable

The thermostat doesn't open until 82c. So the radiator and top hose should be cold if coolant temp is only 60c.

Not sure about that small hose. Can't remember where that one connects at the other end. It could just be normal circulation. Coolant level is also low which may make it look worse. Should be on the seam of the tank or even a little over that.

If you want to prove whether it is the headgasket or a crack in the engine then use a CO2 sniff tester on the coolant. You can buy them cheaply online, or if you have a trusted local garage, they might test it for free for you.

2 minutes ago, TomsFocus said:

The thermostat doesn't open until 82c. So the radiator and top hose should be cold if coolant temp is only 60c.

Not sure about that small hose. Can't remember where that one connects at the other end. It could just be normal circulation. Coolant level is also low which may make it look worse. Should be on the seam of the tank or even a little over that.

If you want to prove whether it is the headgasket or a crack in the engine then use a CO2 sniff tester on the coolant. You can buy them cheaply online, or if you have a trusted local garage, they might test it for free for you.

Thanks, I will get the co2 test from Amazon and check.

From the photo below does any of the reading look wrong, I took the ready from basic reader as I drove the car to test

Interesting to see so much difference in temp between pre-cat and post-cat sensors. It might still be trying to regen, but would expect nearer 500c for that.

NEGATIVE temperatures?
EOT -40 degrees implies to me that a sensor may be faulty or a wiring fault?
FIT is going negative?
Unless the reader is set incorrectly or some other stupid reason and I don't know what the labels mean (ECT = Coolant, looks OK, outside air temp would perhaps affect ECU operation?).

51 minutes ago, Shearers said:

NEGATIVE temperatures?
EOT -40 degrees implies to me that a sensor may be faulty or a wiring fault?
FIT is going negative?
Unless the reader is set incorrectly or some other stupid reason and I don't know what the labels mean (ECT = Coolant, looks OK, outside air temp would perhaps affect ECU operation?).

-40c is default for when the sensor isn't fitted. (EOT - Engine Oil Temp)

FIT is fuel injection timing based on crank angle.

On 4/22/2026 at 7:43 PM, TomsFocus said:

-40c is default for when the sensor isn't fitted. (EOT - Engine Oil Temp)

FIT is fuel injection timing based on crank angle.

On 4/22/2026 at 7:43 PM, TomsFocus said:

-40c is default for when the sensor isn't fitted. (EOT - Engine Oil Temp)

FIT is fuel injection timing based on crank angle.

update.

o2 test clears

I had egr replaced and white smoke and fan was still running so i replaced it back to original.

I got forscan. Clear learned values for dpf and all error. There still some error.

I feed the latest data to ai, ai think my egr and o2 sensor not working due to wiring issues. o2 sensor value was supposed to calculate dpf values.

i have cleaned o2 sensor and dpf doesnt look that clogged from the sensor hole.

car is not smoking anymore and radiator fan is also not running at full speed. not sure how to fix the issues forscan is showing

I have upload data photo before clearing error and learned values using forscan and after

AI response

To explain this simply, your car's computer (the ECU) is reporting "impossible" or "maximum error" values for these systems. This usually happens when a sensor is physically broken, unplugged, or has a blown fuse.

Here is the brief breakdown based on the data in the images:

1. EGR System (Exhaust Gas Recirculation)

• The Problem Value: EGR_A_ERR at -100.00%.

• Brief Description: This represents a "Total Command Error." The car is telling the EGR valve to move, but the valve is providing zero response or is stuck in the opposite position. It’s like pressing the gas pedal and the car doing nothing—the 100% difference proves the system has failed or is jammed with carbon.

2. O2 Sensor (Oxygen Sensor)

• The Problem Value: Code P0030:13-2F (Circuit Open).

• Brief Description: This is a hard electrical fault. "Circuit Open" means the electrical path to the sensor's internal heater is broken. Because the sensor can’t heat up to its working temperature, it cannot provide the data needed to clean the DPF filter.

3. EGT Sensors (Exhaust Gas Temperature)

• The Problem Value: EGT11V and EGT12V at 4.99 V.

• Brief Description: In automotive electronics, a reading of 4.99V or 5.0V is a "pegged" voltage indicating an open circuit. The computer is seeing no resistance, which usually means the wires are cut, the plug is disconnected, or the sensor has failed internally.

1 hour ago, Hamid said:

I feed the latest data to ai, ai think my egr and o2 sensor not working due to wiring issues. o2 sensor value was supposed to calculate dpf values.

i have cleaned o2 sensor and dpf doesnt look that clogged from the sensor hole.

Good to see you've made some progress with this.

There are a few issues here though. The O2 sensor can't determine DPF values. That's done from the pressure sensor.

Also you can't see the DPF from the O2 sensor hole. The top section is the catalytic converter. That shouldn't look clogged at all.

The O2 heaters burn out quite often, so you probably just need to replace the sensor to get rid of that code. Part number 1697560. I would stick to a known brand if not genuine Ford.