2001 fiesta mk4 1.3 - fiesta mk4 Evap

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Mon 19 Aug 2019 21:40
2001 fiesta mk4 1.3 - fiesta mk4 Evap - Harel

Hi all

Car is 2001 Fiesta mk4 1.3 Endura-e engine

problem is car jerks under acceleration but under some circumstances:

it starts at around 2100rpm until it reaches around 2600rpm

under or above these rpm car accelerates fine

i havent paid attention much but i think it happens only when engine is warm

so that brings me to think it has something to do with the Evap system

i have to say i been having this issue for quiet a time now but it had only a slight hesitation during the acceleration but now the hessitation seems to increase

what do you guys think?

i was thinking about disconnecting the purge valve electrical connection and test drive the car so i can isolate the problem to the Evap system if the jerks wouldnt occur

is it safe to drive the car with the purge valve disconnected?

thanks in advance

Harel

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Mon 19 Aug 2019 22:44
2001 fiesta mk4 1.3 - fiesta mk4 Evap - elekie&a/c doctor
What makes you think it’s the evap system.? Hesitation/ jerking on these is often a problem with the ignition system . Spark plugs / ht leads / coil are the usual suspects. I would also check the engine breather pipes for any cracks / splits.
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Mon 19 Aug 2019 23:03
2001 fiesta mk4 1.3 - fiesta mk4 Evap - Harel

well..the fact the hesitation happens on a certain range of rpm plus that im almost sure it doesnt happen on a cold/warming up engine made me suspect the Evap system, since the haynes manual states that the purge valve opens when engine is warm and under load but i could be wrong as well..

im going to change the spark plugs sometimes soon if i can just undo them because the sit there for quiet a time and are pretty tight on the head, also going to replace the fuel filter as well

i have checked the breather pipes and they are clean with no cracks , also i had the filler cap a good cleaning with petrol few weeks ago

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Tue 20 Aug 2019 13:27
2001 fiesta mk4 1.3 - fiesta mk4 Evap - Harel

Any ideas?

Edited by Harel on 20/08/2019 at 13:28

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Tue 20 Aug 2019 15:04
2001 fiesta mk4 1.3 - fiesta mk4 Evap - elekie&a/c doctor
So you have replaced the spark plugs and the ht leads and the problem still exists? Any fault codes logged on the diagnostic system ?
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Tue 20 Aug 2019 16:16
2001 fiesta mk4 1.3 - fiesta mk4 Evap - Harel

I didn't have the time to do the spark plugs yet, and unfortunately I don't have access to scanner tool.

I suspect the spark plugs might be the reason for this but I also wonder why this happens only at a very certain rpm range with the engine warm ,,I would think if it was a spark plugs fault then the hesitation would be all over the place

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