Hello everyone!
I have a Ford Fiesta from 2012, 1.4 petrol engine, 97 horsepower, bought by me from the dealership.
I have a problem that 3 different mechanics and not even the Ford dealership could not solve.
The car is equipped with an LPG system, but the problem that I have only occurs when it runs on gasoline, and it has appeared before installing the LPG system.
When i start driving the car with a cold engine, the car does not accelerate smoothly. It has a trembling of the engine and the car is running slowly, even if i put the pedal to the floor.
When the RPM exceeds 2000-2200 revolutions, the car accelerates normally. When it drops below this value, the shaking appears again.
The problem disappears when the engine switches to LPG, everything works perfectly on LPG.
On the advice of the mechanics and the Ford dealership, I have changed the following with new parts:
- engine temperature sensor,
- battery,
- the petrol pump, complete with internal petrol filter,
- throttle Body,
-spark plugs, spark plugs wire, ignition coil,
- fuel injectors.
After I changed the injectors, I drove the car only on gasoline and for two days it ran perfectly.
After these two days the problem returned as before.
There is no error on the tester, I don't have any lights on the dashboard.
I repeat: the car runs perfectly on LPG, the problem is only on petrol.
What else could I change? I ended up changing parts myself because I have no mechanic to go to.
They tell me that they don't know what to do, especially since I have no errors on the tester.
P.S. I'm from Romania and I hope you can help me with any advice.

5 hours ago, MarianGBR said:

Ford Fiesta from 2012, 1.4 petrol engine, 97 horsepower, bought by me from the dealership.
I have a problem that 3 different mechanics and not even the Ford dealership could not solve.
The car is equipped with an LPG system,

Sorry @MarianGBR but a Fiesta with LPG is just not a thing in the UK. I doubt if there will be anyone able to help you.

I understand but the problem is only on petrol. Let,s asume there is no LPG system on the car. Where should I look further?

Normally on a petrol engine with the fault you have I would advise new spark plugs, new HT leads, and new coil pack. However, I see from your list that you have already replaced these things. If the engine has been mostly run on LPG, I'm not sure what affect that will have had on things like carbon deposits and valve wear.

Perhaps @TomsFocus might have some ideas of what to try?

As above, I don't have any experience with LPG at all.  Is there any reason that you need to be running it on petrol?  Does it cold start on petrol before switching to LPG when warmer?

 

Given all of the parts you've replaced so far, I'd be looking at the MAP or Lambda sensors.  However, both of those must be used when running on LPG.  And the lambda sensor isn't used at cold start anyway, it needs to warm up before it starts working correctly.

The car always starts on petrol and when the engine reaches about 40 degrees Celsius it automatically switches on LPG. 

I will go forward and change the lambda sensor. I will keep you update after i will change it.

Hello!

Yesterday a have managed to change the upstream oxygen sensor and the problem still persist with the same hesitation in accelaration until 2000 rpm. I have no more ideas on how to proceed next. 

What grade of petrol do you have in your country?

I mean what RON level, we use RON in UK, 95RON is minimum, 97-99 RON is super unleaded.

What is yours?

On 3/12/2024 at 5:48 AM, MarianGBR said:

Let,s asume there is no LPG system on the car. Where should I look further?

Using the assumption above, I would suggest reducing the spark plug gap from 1.3mm to 1.0mm and see if that resolves the issue.
 

Ok Dan62. It worth a shoot. I will let you know after a few days.

So, i have checked the sparks gap and they are at approximately 0.8 mm.

I have changed the MAP sensor and the PCV valve. The problem persists.

A few days ago the orange check engine error appeared and it gave the error "P0172 system too rich (bank 1), no symptom, pending". I cleared the code error, and no signs of improvement.

I do not know what to change next. Maybe the car.😂

 

I think, perhaps, you have to suspect a bit of valve wear.

Head off I'm afraid