Technical ECU/Coil problem - further question

[judderbar]

Thanks Judderbar. I wouldn't say that I know what I'm doing but I am very keen to learn! Are there any resources you could point me to that would help me to identify where the problem is?

The local garage had another look at it yesterday and managed to get a better diagnosis; the error message I've been told was 'random multiple misfire on coil 1'. They've said that they'd recommend taking it to a Fiat garage as they'll have better diagnostics kit. I'm keen to try to sort it myself if possible though as the nearest Fiat garage is quite a drive away and the 2-cylinder misfire is no longer intermittent. Don't want to risk causing further damage by driving it a distance...

I do not know of any online resources you could try.

Do you have a voltmeter?

Are you able to connect two wires to a 75W light so you can use it as a test light and connect the voltmeter across the light? Connect one end of the light to the battery negative terminal - the ground

Check the brightness of the bulb and the volts measured on the coils wires and compare the result you get with the good coil.

Do not turn over the engine.

If you do this properly you will be able to get brightness or volts for the fusebox side of the coil and the same measure for the ECU side of the coil and be doing that when the wiring can pass a 6amp current thru the bulb.

Report back.

 

[Tim C]

Thanks judderbar. I decided that tracing a wiring problem is probably beyond me so I took it to a Fiat garage. After 2.5 hours labour (and £200) they've traced and replaced some corroded wiring but concluded that the ECU has gone too.

Rather than paying the £500+ they've quoted me to replace the ECU I think I'll buy one and fit it myself - it was so easy to take it off when I was checking the connections. I've heard that some of the ebay ones are alright - can anyone recommend a place to get a decent ECU at the lower end of the budget scale?

 

[bluejohn125]

Talk to a company called ECU testing in Derbyshire, they are a proper professional outfit who will be able to sort you out though not at bargain Ebay prices. They will know all about these issues with the Punto and sell you a recon unit or fix yours quickly. They may also know a local specialist garage or electrician for you who uses their services, if you go to them then you could then be sure that someone who knows your car and the company can make sure that the problem gets fixed.

You may get away with optimism and guesswork and a cheapo solution, but I'd be cautious.

 

[Tim C]

An update on the story above:

After having a Fiat mechanic unable to find the exact source of my ecu problem I fitted a new ecu (not brand new). I had sent the old one to ecu testing but it was unrepairable. The car worked perfectly for a few months with the new ecu then the problem recurred. As it stands the car almost always runs on two cylinders when started then usually (though not always) kicks in to running on all four, sometimes after 30 seconds and a few revs but sometimes not until it's up to temperature. Sometimes it can't be persuaded at all though and it just misfires. Even when it does work properly, it's particularly prone to reverting to misfire mode when restarting the engine at the petrol station, for example.

What's strange is that it seems to work fine first time if it's been left for a while without being used.

I thought I'd put an update and see if anyone had any final suggestions before I consign it to the scrap heap. It's a real shame because it's a great car otherwise but with an intermittent and unpredictable misfire that a fiat mechanic couldn't diagnose the source of, it seems like there's not much else I can do.

If anyone wants it to have a play with, you're welcome to it unless I can get something for it part exchange!

 

[atom0007]

Out of interest, how do you know it is 2 cylinders it is misfiring on?

 

[Tim C]

Good point - I'm just assuming that as that's what the original diagnosis said. It could have changed in the meantime.

 

[burrowsdeano]

Where abouts are you based?

 

[Tim C]

I'm north of Cardiff.

Here's what happened today, as an example:

Made three short journeys within an hour. The car worked perfectly the first two times but the third time it started on a misfire and stayed like that until I got home. The only difference was that the third time the engine was already up to temperature when I turned it on. It's a mystery to me!

 

[atom0007]

The reason I ask: how do you know it's a coil pack error.

For example, I had a failing hg and the misfire was temperature dependent.

 

[Tim C]

I don't think that it is the coils at fault now - I would guess that the fiat mechanic would have diagnosed that and the coils (and plugs and leads) have been replaced with new ones.

That's interesting - the fiat mechanic had tested the compression when they were looking for the fault and said it was all fine. Could it still be the head gasket even if compression was ok? Thanks for the input!

 

[atom0007]

Possibly. I've not really been following this thread, but it may be worth investigating other sources of misfire before giving up on the car

 

[Tim C]

That was my opinion too but two mechanics, one from fiat, spent several hours trying and couldn't come up with anything so I wasn't sure what else I can do really. I'd rather not give up but was thinking it might be best to cut my losses at this point.

 

[judderbar]

That was my opinion too but two mechanics, one from fiat, spent several hours trying and couldn't come up with anything so I wasn't sure what else I can do really. I'd rather not give up but was thinking it might be best to cut my losses at this point.

The current misfire does not seem obviously related to the previous fault because the car can run normally and those ECU/coil problems are usually all or nothing.

How many expert mechanics have looked at the current fault?

 

[Tim C]

That's true - I haven't had the fault diagnosed since it recurred. That said, the symptoms are exactly the same - it was also intermittent the first time (for a long time at least) and it is again now, hence me thinking that it's likely to be the same. All or nothing is exactly what it hasn't been, it's been intermittent almost entirely since it first started. I realise it could be something new this time though - I might just be unlucky. That's what is making me think I'll cut my losses. The previous round of diagnosis and parts cost about £500 and lots of time - that again and we're exceeding the cost of a replacement car.

 

[bencey]

I'd ask your mechanic friend to do the compression test on the engine when hot and cold.
And a cylinder leakage test.
Those would rule out any internal engine failures.

I've recently worked on a 1.2 panda, It would randomly start to miss fire when hot, cold, morning, night... Completely random.
I eventually found the pre cat lambda probe was switching from rich to lean waaaaaayy too slowly.
So the fuel mixtures going in to the combustion chambers was miles too rich.

 

[Tim C]

That's really interesting - thanks for replying. So was yours a case of just replacing the lambda sensor or was there something more complicated to solve it?

That sounds like mine - pretty much random. The only consistent thing is that it only misfires upon starting it up. If it's running OK it'll never start to misfire unless it's turned off and restarted. Likewise if it goes from misfiring to normal whilst it's running, it won't go back to a misfire.

 

[Antony]

After reading this thread I was starting to think of fuel mixture etc. I would definitely make the Lambda sensor and it's connections my next step.

 

[Daihandley88]

Hi lads! Sorry to comment on your thread but I'm also having problems with misfiring grande punto 1.2. All has been well until this morning when I changed the plugs and leads because they've been on a while. Put everything back together, starts it up and it's missing really badly!!!! All leads are on tight and earths are clean. Just wondering if the coil pack is faulty as last time I changed the plugs and leads the same thing happened and I had to get a new coil pack

 

[Tim C]

Final update on this - the car eventually was misfiring constantly rather than intermittently. This is exactly what happened the last time before I replaced the ECU and the Fiat mechanic couldn't solve the problem, so I made the decision that it wasn't worth pursuing it further in terms of time and money.

I bought another, almost identical Punto for a few hundred quid and it's running perfectly. Seems a shame to write off the first car but it's just not worth pursuing in my opinion.

Thanks to everyone who commented with advice. If there's anyone in south Wales who would like the misfiring car for free, you're welcome to it if you can collect.