Technical Misfiring when cold and now when warm aswell

[FrederikN]

Hi Fellow members.

I have been having a problem with my punto mk2 8v for a while, when cold.

Where it would judder as if it with misfiring, as you accelerate. That would then disappear, after you've run the car for 2 minutes time. The fun thing is that, the car will start right when you turn the key from cold. But when warm it turns over just about to start, then misses and then starts. Strangely no running issues when warm, until tonight...
Now the car almost sounds like it runs on 3 cylinders when you accelerate, and "farts" out of the exhaust. Although there is no problem with the idling, and runs on all 4. The EML comes on and flashes as i tried to push the car a little, but went away again, as i leaned off.

I've had the pre-cat lambda sensor, in mind for a while. As i've been thinking that it might give wrong values to the ECU, and therefore results in these problems.

What are your thoughts? any advice would be great. I'm thinking to stop by a garage tomorrow and get a tester on it, to see what the fault may be.

I've recorded 2 videos, that i can try to upload on request.

Regards Frederik

 

[Ziggy122]

Sounds like the classic misfire
You've got the symptoms to match

EML flashing
Lacking power
Hesitating
Started off worse when cold

It points to the fact the HT leads are pretty much ready for replacing there
And tbh - i'd throw a set of leads on there too

Ziggy

 

[FrederikN]

Hi Ziggy thanks for the response

It just doesn't make sense to me since I replaced spark plugs, leads and coil packs in the fall to get this issue solved, and it hasn't helped. So not to say you cannot be right but it would just not fit in my head

Frederik

 

[Twotoncarman]

what diagnostic codes are you getting ?

 

[Ziggy122]

If its running like **** when cold and aint getting much better when warm

I'd be tempted todo a compression test on it my friend
A code read is always a good idea

Ziggy

 

[FrederikN]

I'm about to go out and check. But the initial problem, was just, that it was lacking power, for the first 2 minutes that you drive, and then disappear. Only symptoms when warm, was that the starting of the car, took longer than when cold. But it seems like it has the same problems as my grandmothers stilo, which was the coil packs, as of now. Head gasket was changed last spring

 

[Twotoncarman]

I wouldnt jumpt to any conclusions until you get a diagnostics check.
Make a note of the readings and codes before you clear them !. note, there is a log file in the mes directory with the details in if you use MES.
The OBD conenctor is for a reason. Too many jump to checks and substitutions before electronic diagnosis. The electronic diagnosis should be your first action.
Hope you sort it.

 

[FrederikN]

I've just got it diagnosed. It said misfire cylinder 4. The mechanic I got it diagnosed by thinks it's the fuel injector. But my local fiat garage says, it can also be the ECU acting up, or bad connections to the ECU. They will put a tester on it now as well. Thanks for you help fellas. I rely on my car, to get to and from work, so that's why I'm a little eager to get the problem solved

 

[Ziggy122]

Punto injectors rarely go wrong - and i mean rarely
But there some out there that fail


Since the 8v uses a wasted spark system, then cyl1 would also misfire if it was
A Coil or an ECU releated fault. There have been some coils that have broken down 1 side first before the other shortly followed

My advise is this
Since there is a suspect injector fault - swap the injector over to another cylinder, Say no2, and see if the fault code moves to cyl2
if it stays on cyl4, then your looking at another issue been potential wiring or Ecu fault

Cant remember if injectors are paired or not, dont think they are, but it could be a simple connection issue or wiring issue

Ziggy

 

[FrederikN]

Okay, so what you're saying is, as it sounds now it's most likely to be an injector problem, since it's only misfiring on 1 cylinder?

I just don't believe that it can be the coils, since they're almost new.

Since i'm not that comfortable with sorting the electrics, i probably have to pay, my way out of it, if the ECU is the problem.

Frederik

 

[Twotoncarman]

Hi Fredrick
remove all the spark plugs and check the colour and condition. Take a pic if possible. (note where they came from)
While they are out I would do as Ziggy said and do a compression test.
If you get a low reading on the faulty pot, then add half a teaspoon of engine oil and try again. This will indentify a ring / bore / piston issue as opposed to valves or head gasket.
It is always beneficial to do the test with and without the half teaspoon of oil. It gives you muych more information.

 

[MaNIaCdk]

Hi Frederik

I know this is an old thread, but did you sort the problem? If you did, what was the cause of the problem?

I'm having a kinda similar problem, coils, plugs and leads are new, not firing on cyl 4, injectors swapped 1 & 4 same problem. If I swap injector wire 3 & 4, the problem moves to cyl 3.

I am suspecting ECU fault, but I dont want to order a virgn one just yet :idea: Havent done a compression test yet either.

 

[flisko]

Hi Frederik

I know this is an old thread, but did you sort the problem? If you did, what was the cause of the problem?

I'm having a kinda similar problem, coils, plugs and leads are new, not firing on cyl 4, injectors swapped 1 & 4 same problem. If I swap injector wire 3 & 4, the problem moves to cyl 3.

I am suspecting ECU fault, but I dont want to order a virgn one just yet :idea: Havent done a compression test yet either.

what error code do you got? im having similar problem on a grande punto

 

[MaNIaCdk]

what error code do you got? im having similar problem on a grande punto

Take a look at my thread here, it has a lot of details in it http://surl.dk/hxg/