Seeking advice on jerking problem (Lancer Sportback 2.4)

[dexidle]

Hello friends, im a newbie here. my lancer sportback recently got jerking problem after routine service done at glenmarie mitsubishi service (change engine oil & spark plug @100k millage). First time i noticed the jerking i suspected it might relate to spark plug or its cable and second assumption could be my cvt gb. Its always happend whenever i start driving after stop (low rpm) and only several time occured at high speed. I sent back the car to them to troubleshoot, and they did troubleshooting connecting their laptops with my car and drive for awhile,then they suggest to change air filter which i think it nonsense at all. So i just change it with hopping that problem solve :D and as expected the problem is still happened. I called them and they ask me to send back to do troubleshooting again but now i dont want to waste my time sent back my car to them.

I need some advice from otai here or might be someone else have experice with this kind of problem, or could someone suggest me which service center or mitsu specialist workshop.

 

[yh4everlim]

is the spark plug or coil is connected properly??
since computer cant detact any fault i think it is because something loose or not connected properly, or even the spark plug gab prob.. did the guy at the sc double check on this or juz terus connect computer for troubleshooting?

 

[johnsonlam]

the jerking is constant on all speed? or when moving from standstill?

that symptom might be the MAF sensor soiled.
or
try reset the ecu if it helps.. take off the battery +ve terminal for 10mins..and out back.

 

[dexidle]

is the spark plug or coil is connected properly??
since computer cant detact any fault i think it is because something loose or not connected properly, or even the spark plug gab prob.. did the guy at the sc double check on this or juz terus connect computer for troubleshooting?

So far, i did try disconnect and reconnect the male-female 3 wire socket for each 4 ignition coil. And not tried yet to pull out all the coil & lead, because i was thinking that the plug lead should connect properly with the spark plug since the coil & lead properly bolt. Is it possible some of the spark plug is faulty? or one of the ignition coil is faulty? if the ignition coil is faulty cant it be detected by the computer?

The guy at sc just rev the engine and idling for awhile and then just connect the laptop and drive my car out from the sc with the laptop connected.

the jerking is constant on all speed? or when moving from standstill?

that symptom might be the MAF sensor soiled.
or
try reset the ecu if it helps.. take off the battery +ve terminal for 10mins..and out back.

the jerking not constantly occur, sometime at high speed and mostly it happen when moving from standtill. What i was thinking is if it relate to sensors it should be detected by computer right? if maf sensor soiled, can i DIY clean it with something like anti rust spray or is it require any special liquid to clean it?

BTW, thanks guys for your reply

 

[yh4everlim]

sometimes computer cant tells if there is a bad reading from the sensors.. unless the sensor is not working at all or a shorted wiring, better let outside workshop check for u first other than the sc... the problem can be easily detect with proper troubleshooting but not juz only count on a scan tools.. n also.. avoid machanics that ask u to chg this and that, unless they proven the source of problem.. gd luck

 

[nyantong]

Its quite possible the ignition system is faulty, since it only happened after service and the plugs were replaced. Remove the coils and
cables and check for any damage or oil stains on the coil and cables. Sometimes the coil or cable can also cause misfiring due to damage
internally during removal when servicing.

 

[DanzEterna]

petrol filter?

 

[Mitevo7]

Actually my GT also jerk a little bit but only when in traffic jamme. Have you flushed out the CVT fluid and replace with a fresh one? That might help ...

 

[dexidle]

last weekend i already check all cables and each coils, re stretch the spring (inside the rod) that connect to the plug head.. and hoping the problem gone, but it still happened, now i suspect the plug itself. Guys does the plug with wrong code can cause this problem? because my engine 4b12 using NGK FR5EI, inspira & GT (4B11) using NGK FR6EI which is physically same size actually. I was thinking that sc guys might install wrong spark plugs. This things flash in my mind (that might be wrong plug installed) when i go to spare parts shop looking new plugs they give me FR6EI they said same maa.. boleh masuk and bigger number much more better.

 

[nyantong]

last weekend i already check all cables and each coils, re stretch the spring (inside the rod) that connect to the plug head.. and hoping the problem gone, but it still happened, now i suspect the plug itself. Guys does the plug with wrong code can cause this problem? because my engine 4b12 using NGK FR5EI, inspira & GT (4B11) using NGK FR6EI which is physically same size actually. I was thinking that sc guys might install wrong spark plugs. This things flash in my mind (that might be wrong plug installed) when i go to spare parts shop looking new plugs they give me FR6EI they said same maa.. boleh masuk and bigger number much more better.

In that case you have to check with the sc about this. Or another way is to buy FR5EI and install it yourself and see if it makes a diff

 

[k0pi]

how heavy of the jerks you're experiencing?
if little jerks (and happens at certain range of rpm) - it may be the plugs, plug cable or ill ignition coil - since the plugs heat range changed to only +1 which may cause irregular detonation at some rev points if the engine is sensitive enough, especially when driving in hot conditions. Jerks will occur less in cold environment (during rain or chilly air) at low rpm (<3500rpm) and almost none at mid-high rpm.

if the jerkings are constant throughout all rpm - refer to johnsonlam's suggestion.

if you're experiencing big jerks that actually slumps down the car while you're accelerating (like fuel starvation) - this goes to something else (that may probably led to ignition timing went wrong or soaked plugs) and needs someone to go through the many possibilities from clogged fuel filter, electronics (ECU, wiring, sensors & connectors, throttle) , vacuum port leaks / improper connection of vacuum hose, or the cvt gearbox (but doesn't usually problem symptom to the cvt gearbox will just tend to shift up and down irregularly or stuck to over-revs?). JUST IF - you find the water temp being abnormal - do also check DIY the radiator for constant bubbles that tend build up and spill out after 2-3mins like you just open a bottle of Pepsi. A pinhole leak from the cylinder head gasket that kicks cylinder gas into the water jackets could also contributes to small jerks.