Anyone with Ford Fiesta (2005) Knowledge ? Momentary loss of acceleration, then normal.

So the symptom are>> car used daily, starts normal, drives normal for the most part. Then whilst driving as I try to accelerate, it holds back, wont pull cleanly a little chugging (mild) then back to normal driving. Its had a service in Feb , new plugs, oil , oil filter air filter, new coil pack and lead in July. I replaced the lambda in Feb but to be fair, it was an unbranded one from Amazon (this is the point where you guys cusre me...lol) It has thrown up a lambda bank 1 sensor 1 circuit fault a couple of times (with engine warning light) but this goes off within a day...thats it, I also changed the fuel filter last week just in case but issue still remains. Could it just be a dodgey Lambda ?? No warning lights on dashboard, no fault codes ?

 

I have just passed my 1.25 2004 fiesta onto my daughter. All serviced and 100%, lots of new bits recently done, coil pack, plugs, rear springs, shocks, clutch, timing belt. I drove it to work for the last time last week and started it up, moved it 30ft. Restarted it a minute later and the engine mil light came on. Plugged in my code reader and it said the heater in o2 sensor b1 s1 was faulty. Cleared the code and it has not come back. Checking the sensor and the voltage changes from 0.1 to 0.9v so all OK. It might be starting and stopping and then restarting has made the fault temporarily show up. If the o2 sensor is faulty the long term fuel trim will show a positive or negative offset. It should stay close to 0.

Since having it for 14 years the only thing that caused me problems was the throttle position sensor connector. It is under the inlet manifold and can be disconnected and cleaned with wd40 or contact cleaner. If engine dirt or water gets in the connector it causes the car to judder. I cleaned the connector 2 times and on the third time it broke trying to clean it with cotton buds and it ended up soldering wires directly to the throttle body and crimping them into the loom. No more judder problems. I haven't had to clean the throttle body inside.

Check your short term fuel trim to see if it is adding or removing fuel. That might give a clue to the problem.

 Thanks, its just so frustrating that I cant pin it down to just one specific thing. With no fault codes to direct me, its just a case of replacing parts likely to cause the issue, cheepest first. And because its intermitent the syptoms could be one of several components. AARRRGGGHHHH 🤬

Hi, New hear. Might be the amazon lambda senor. Also replace the spark plug leads. Had a similar fault and the leads where the problem in the end.

Definitely worth replacing the lamb sensor with a better quality type. You could try cleaning the old one and putting it back in. Also cleaning the throtyle position connector is worth doing.

I notice when changing my bosch plugs 1.3mm gap to new ngk ones the gap was 1.0mm. Replacing spark plug no 2 fixed a missfire on cyl no 2. This was picked up by the code reader and resulted in engine judder. This was why I cleanened the tps connector a 3rd time and broke the connector thinking that was the fault.