General Another Issue - Misfire 1.4 8V

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General Another Issue - Misfire 1.4 8V

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Aug 23, 2015
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Hi All,

Car developed a slight misfire:

Occurs between about 1200 & 1500 RPM only and most noticeable on lift off of throttle when it can be clearly heard and felt. If slowing down in 4th or 5th, when engine speed hits above range the car jumps a bit sort of like a kangaroo start from bad clutch control.

No check light
Plugs replaced about 1000 miles ago (gen. Fiat parts) and old plugs looked OK
HT Leads look in excellent condition
Air filter & oil filter all new and correct.
Breathers not split
Fuel economy not changed
No noticeable hesitation on acceleration
Worse when car is on "choke", i.e cold

2006 1.4 8v Active sport.

Any suggestions would be appreciated.

Thanks in advance


Ben
 
So you don't have this misfire feeling if you accelerate hard in 4th from ~1500rpm ?
 
I didn't but I do now. Power is definitely down below 2000 RPM and I can feel a slight miss occasionally between 2000 & 3000 RPM.
Changed HT leads yesterday, no change. Drove into town to get a crank sensor today (not fitted yet) and it appears to have got slightly worse. Will fit tomorrow, hoping it sorts the issue.


Cheers

Ben
 
Check for errors even if there is no MIL

Clean MAP sensor and intake valve (you can search here on how to do these)

If you replace crank sensor perform a phonic wheel re-learn too.
 
Hi! How does misfiring sound and feels like? My FGP 1.4 8V (MT) does jerk a little hard in the first to second gear shift when I did not control the throttle gracefully. Pretty sure it isn't my driving though.. :p
 
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No EML, just missing and down on power which is paticularly at low revs.
When at idle if revved the miss can be heard and felt from around 1500 to 1000 as the revs drop away back to idle.

Cheers

Ben
 
Have you scanned for any error codes?

If it's misfiring then I'd have thought something will be logged.

Surely it's better to check for errors first before taking a stab in the dark and ploughing money into parts that could be working just fine.
 
I have not had anything scanned as yet, I have downloaded the software but need to get a cable for it for my laptop. I went for a new crank sensor as it seemed like the most obvious thing given the symptoms.

Cheers

Ben
 
I've now scanned the ECU with the free version of Multi ECU Scan, recorded no fault codes.

I was going to take the MAP out to clean it but, the only rusty screw on the whole damn car holds it in place in the plastic inlet manifold. Brand new T25 bit just disintegrated it and it's stuck fast. Any ideas on how to get this to shift?

I think it is going to be a case of just changing sensors / electrics until I sort it.

Would a faulty coil pack make cause missing throughout the rev range or only at a certain point, my instinct tells me the latter?

Cheers

Ben
 
Hi All,

I still have this misfire and I am now down a little on power too and having to change down for inclines that did not once require it. Car is OK on the flat but lack of pull is noticeable on hills.

Misfire occurs between about 1100 RPM and 2200 RPM and can be felt as a hesitation / general lack of power in that range. Also can be felt and heard as revs drop away around 1500 - 1100 RPM

So far I have done & checked the following:
Changed Spark plugs & HT leads genuine fiat, gapped correctly
Breather hoses - all OK
Cleaned throttle body and performed ECU relearn process
Changed crank position sensor and carried out phonic relearn
Have run car with MAP sensor disconnected, no change other than EML coming on (still cannot get MAP off car due to rounded retaining screw)

No fault codes logged by ECU scan, f uel economy not changed.

Any ideas would be very much appreciated,it's driving me nuts!

Cheers

Ben
 
Check the Air/Feul ratio whit a emmesions tester and post all of the figures here, both idle and in the problem era. What is the feultrim (both long and short). Timing of the cambelt ok? feulpressure ok?

Do bear in mind that the coilpack also can be faulty
 
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Can I test these things and obtain the required data with Multi ECU scan, including coil pack?

Cam belt has not been changed since well before this issue arose and feels tight so I doubt any slippage could have occurred?


Cheers

Ben
 
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