Technical Intermittent Misfire

[dbergloev]

Hi.

My sister got this 2016 0.9 TwinAir 2 cylinder Fiat Panda. Nearly impossible to find any data on this engine, as most Panda and 500 owners has the larger engines, often with turbo as well.

It has had this issue on long drives in high speed, where it will start to misfire and loose power. Fault codes varies between p0300 and p0302 and at some point it will completly disable cylinder 2. If the engine is turned off for 2 minutes, then she can drive a little while again. It takes at least an hour on the motorway before this happens. City driving is fine. Also outside weather makes no difference. Cold, hot, rain etc. Oil level has been checked and I also replaced the oil and filter a few months back.

I started just changing the spark plugs and coils. It only has two cylinders anyway, but it did not solve anything. Then someone said that the fuel pump may get overheated during long drives. Don't have anything to test something like that with, so I took a shot and just replaced it. But again, nothing solved. I have checked the PCV valve and it seams to be working correctly as well. I am more or less down to the fuel rails or some intermittent electrical issue with a wire getting to warm, but to access the fuel injectors I need to get the MultiAir block out of the way. Does this thing need anything speciealized to get it back in and working again after removal, or is that a safe thing to do? As I said, I can't find any specifications, drawings etc. on this engine. I know how the MultiAir system works in theory, but I have no visuals of how this thing look on the inside. I do know though that I could end up with starting problems, should oil be drained from it.

 

[A3jeroen]

How is the oil? level, weight and quality are extra important for the uniair (valvelifting) to work properly. Pressure may fall too far when the oil gets hot.

gr J

 

[dbergloev]

The oil is fine. Like mentioned above, I have done a complete oil change on the car, and I was very particular about getting the correct oil. Also if oil pressure was the issue within the MultiAir unit, I would guess that it would create issues on all intake valves and not just on cylinder 2?

 

[jrkitching]

Also if oil pressure was the issue within the MultiAir unit, I would guess that it would create issues on all intake valves and not just on cylinder 2?

Inadequate lubrication as a result of poor maintenance by a previous owner could have caused damage/premature wear to the MultiAir unit, and that may be more pronounced in the side that is now giving trouble.

I wouldn't be ruling out the uniair module just yet. Unfortunately I don't know a good way to test it, and replacements aren't cheap enough to contemplate changing it unless you are certain it is the cause of the problem.

 

[The Panda Nut]

This is highly informative. I would change the plugs and coils as the first task.

Fiat TwinAir misfire

Fiat Panda TwinAir 0.9L turbo (2013) I was called in to look at this vehicle, after the garage had replaced both ignition coils and spark plugs, in response to a cylinder number 1 misfire condition…

markstammersdiagnostics.com

 

[jrkitching]

That's an excellent linked post; thanks for finding it. It confrms that a problem with the uniair module may, and indeed is quite likely to, affect one cylinder only.

Of course, if that's what's happening here, then replacing the uniair module is the only possible fix - changing the plugs and coils will make no difference, other than to increase the final bill.

But as I've said above, the uniair module isn't cheap, and the link in the previous post shows that some advanced diagnostics may be necessary to properly confirm it's the cause of the problem in this case.

 

[Panda IIs]

The oil is fine. Like mentioned above, I have done a complete oil change on the car, and I was very particular about getting the correct oil. Also if oil pressure was the issue within the MultiAir unit, I would guess that it would create issues on all intake valves and not just on cylinder 2?

I have a TA 4x4 (Turboed here in the UK) it is a 2013 car. I purchased it at 4 years old and 45k miles, from a dealer one previous owner, but with no history (I knew the risks and it was priced accordingly). At 50k miles I encountered similar issues. First of all, and it is too late now for you, if you have a misfire swap the coils don't replace them, this identifies if there is a failure. After I went through a similar pain to you (with an independent specialist) we gave up and went to a main dealer who did indeed diagnose a failed UniAir module. They replaced the unit with a 10% discount from FIAT as I raised a complaint with their customer care arguing that such a major item should not have failed so soon; this was a weak position since I had no service issue and oil is critical to the function - it's essentially a pretty fine tuned hydraulic servo valve.

If you suspect the injectors then I would run some cleaner through the fuel system or give it some high octane unleaded for a while (will improve economy in my experience) and see if the problem returns. I'd expect other codes if it was a fuelling issue.

One outcome of the failed uniair unit was a worn out clutch as the car was limped around on essentially one cylinder.

 

[dbergloev]

I have been suspecting the uniair module for some time. But it does also seam that this is the general assumption, just because the car has one. So I have tried to stay pretty neutral when trying to diagnose it and just think of it as any other car with similar problems, which is why I started with the plugs and coils.

One thought though. After I replaced the full pump, the car actually ran for two months without any issues. A number of variables could account for this. Maybe the whether was just right or something. But let's say that the pump was actually the problem, and the new pump broke within it's first two months (don't have anything to test a pump with), what could cause something like that? Blocked return line?

Maybe I just need to give this thing to a garage with proper testing equipment.

 

[Panda IIs]

I have been suspecting the uniair module for some time. But it does also seam that this is the general assumption, just because the car has one. So I have tried to stay pretty neutral when trying to diagnose it and just think of it as any other car with similar problems, which is why I started with the plugs and coils.

One thought though. After I replaced the full pump, the car actually ran for two months without any issues. A number of variables could account for this. Maybe the whether was just right or something. But let's say that the pump was actually the problem, and the new pump broke within it's first two months (don't have anything to test a pump with), what could cause something like that? Blocked return line?

Maybe I just need to give this thing to a garage with proper testing equipment.

I'll repeat my suggestion above; if you think it is a fuelling issue then run some injector cleaner.

When you changed the fuel pump did you happen to change or top-up the engine oil? If so then perhaps after two months it is ready for some more and the UniAir unit is complaining?

I believe you need the full on FIAT diagnostics to diagnose UniAir malfunctions but I may be wrong.

 

[dbergloev]

I'll repeat my suggestion above; if you think it is a fuelling issue then run some injector cleaner.

When you changed the fuel pump did you happen to change or top-up the engine oil? If so then perhaps after two months it is ready for some more and the UniAir unit is complaining?

I believe you need the full on FIAT diagnostics to diagnose UniAir malfunctions but I may be wrong.

I did not top-up the oil. I have been keeping a very close eye on the oil level, because I know how much the uniair module rely on it.

I have already added valve/injector cleaner to the tank, but it will take some time to have an apparent effect. However I can't see how injectors can overheat a full pump?

I think your right about the diagnostics. I don't have the equipment to perform similar tests to the link provided by @Panda IIs'' . I have a multimeter and a simple ODB reader :'D

 

[jrkitching]

I have been suspecting the uniair module for some time. But it does also seam that this is the general assumption, just because the car has one. So I have tried to stay pretty neutral when trying to diagnose it and just think of it as any other car with similar problems, which is why I started with the plugs and coils.

Maybe I just need to give this thing to a garage with proper testing equipment.

I'd agree; the difficulty may be finding a garage with proper testing equipment.

Picking up on PandaII's link, that fault was only found after being referred to an automotive diagnostic specialist by a garage that couldn't figure out what was wrong themselves. It took diagnostic kit costing thousands to find it. Note that the specialist ran all the common tests most garages would do, and found nothing conclusive. It took a highly sensitive real time pressure transducer and digital oscilloscope to work out what was actually happening. It would not surprise me if this level of diagnostics was beyond the scope even of franchised dealers.

 

[dbergloev]

I'd agree; the difficulty may be finding a garage with proper testing equipment.

Referring back to PandaII's link, that diagnosis was carried out by an automotive diagnostic specialist after being referred by a garage that couldn't figure ouit what was wrong themselves. It took diagnostic kit costing thousands to find it. Note that the specialist ran all the common tests most garages would do, and found nothing conclusive. It took a highly sensitive real time pressure transducer and digital oscilloscope to work out what was actually happening. It would not surprise me if this level of diagnostics was beyond the scope even of franchised dealers.

Yes, and it may end up being cheaper to just swap out the module and pray to every God in existence. So I would really like to be able to completely rule out anything that could result in killing a fuel pump, if anyone has some idea what that could be and how to check for it

 

[jrkitching]

I'd have thought that if this were a fuel pump issue, it'd affect both cylinders equally, whereas an intermittent single cylinder misfire is entirely consistent with what we know about uniair faults.

it may end up being cheaper to just swap out the module and pray to every God in existence

I was thinking the same thing myself, but hesitated to suggest it, since it's not my money. I'd say that, by duck logic, the uniair module is the most likely cause of your problem.

 

[dbergloev]

I'd have thought that if this were a fuel pump issue, it'd affect both cylinders equally, whereas an intermittent single cylinder misfire is entirely consistent with what we know about uniair faults.

Yes you're right. A single cylinder makes no sense. It may just have been a coincidence. It's not like this issue has some stable and specific pattern. Some times the car works for days and other times you can hardly drive it at all.

I was thinking the same thing myself, but hesitated to suggest it, since it's not my money. I'd say that, by 'duck logic', the uniair module is the most likely cause of your problem.

 

[dbergloev]

I wonna thank you all. I just needed to run this by someone else, before doing what I sadly already considered. Someone could have had some other idea to a much simpler and cheaper solution. But this seams consistent with my own idea and what I have read everywhere else. No way around it.

 

[The Panda Nut]

That's an excellent linked post; thanks for finding it. It confrms that a problem with the uniair module may, and indeed is quite likely to, affect one cylinder only.

Of course, if that's what's happening here, then replacing the uniair module is the only possible fix - changing the plugs and coils will make no difference, other than to increase the final bill.

But as I've said above, the uniair module isn't cheap, and the link in the previous post shows that some advanced diagnostics may be necessary to properly confirm it's the cause of the problem in this case.

I will try and find Mr Stammers and ask his permission to have the content as a resource on the forum. If he has a garage we all need to know where!

 

[UKRMedic]

In your first post you made mention to the fuel pump...
Recently, though not on a Panda (On a Mercruiser 4.3) I had a misfire issue. Quite bad.
This was the fuel pump, to which the awful fuel we have in the UK had taken it's toll. Replaced, and there ended the misfires!

I had never considered the fuel pump to be the issue, but, the seals internally had perished, so I guess was letting in air?
Fuel pipes also were in pants state, so replaced them.
In my head, fuel pump issues would have resulted in judders or failure to fire. Not misfires. So, learning point for me.

Fuel pump may be a good call not worth discounting.

 

[dbergloev]

In your first post you made mention to the fuel pump...
Recently, though not on a Panda (On a Mercruiser 4.3) I had a misfire issue. Quite bad.
This was the fuel pump, to which the awful fuel we have in the UK had taken it's toll. Replaced, and there ended the misfires!

I had never considered the fuel pump to be the issue, but, the seals internally had perished, so I guess was letting in air?
Fuel pipes also were in pants state, so replaced them.
In my head, fuel pump issues would have resulted in judders or failure to fire. Not misfires. So, learning point for me.

Fuel pump may be a good call not worth discounting.

A bad fuel pump would easily be able to create such issues, if it's having a hard time keeping up. But in your case I would guess that it was a Random/Multiple cylinder misfire issue (p0300) whereas the Fiat almost always has a cylinder 2 misfire (p0302). Each injection valve is connected to the same fuel rail. It does not make sense that a bad pump would only affect a single cylinder. Although the fuel does get pumped into the rail in one end, meaning that one valve is getting the fuel before the other Changing the pump did fix the issue for a while

 

[dbergloev]

It's been a while, but this thing takes some time to properly test in order to make sure that the problem is actually gone.

I stuck to the idea that the UniAir module was acting up. Checking the oil I saw that it was completely black, even though I had just changed it. I ran some oil cleaner through the engine, the thing that you add to the oil and let it run in high RPM for 20 minutes before doing a complete oil/filter change. I did this twice until the oil stayed clean and clear. The car has been running without issues ever since, even on multiple long trips where it was almost certain to act up before. Maybe it just buys time or maybe this fixes it completely, but for now it seams to work and it was cheap. Could be a good thing for others to try before major repair.

 

[The Panda Nut]

It's been a while, but this thing takes some time to properly test in order to make sure that the problem is actually gone.

I stuck to the idea that the UniAir module was acting up. Checking the oil I saw that it was completely black, even though I had just changed it. I ran some oil cleaner through the engine, the thing that you add to the oil and let it run in high RPM for 20 minutes before doing a complete oil/filter change. I did this twice until the oil stayed clean and clear. The car has been running without issues ever since, even on multiple long trips where it was almost certain to act up before. Maybe it just buys time or maybe this fixes it completely, but for now it seams to work and it was cheap. Could be a good thing for others to try before major repair.

There is a filter in the uniair unit. There are posts on here about how to find and clean it, and I believe utube videos too. It might be worth finding and cleaning this. Its a fine gauze unit. Your experience is very valuable. Thanks for posting.

My last TA used to produce a lot of crank case mayo, and my current one is not a lot better. My dealer actually recommended an engine oil flush so you may be on to something here.