Technical I am going crazy with a P0300

[Flat Earth]

Hello everyone!

I have a Fiat Panda 1.2 69HP "born" in 2013 that is throwing P0300, P0301 and P0304 errors. I've replaced sparks, spark plugs, coils, oxygen sensor and MAP sensor, with no luck. The problem persist and it's more accute in hot temperatures. Long fuel trim -55%.

Any ideas? I have no idea regarding how to test the ECU, and since the long fuel trim is really high I'm starting to think that it might be some leaking inyector.

Thanks!

 

[koalar]

Long fuel trims go high with a misfire which fits with the error codes. So the two match. Not that helpful though as it’s only confirming a misfire

If you raise and hold the revs for a few seconds do the fuel trims go back to normal. As in the misfire is only at low revs


What does your scanner read the coolant temperature to be should stay around 90 give or take a bit once the engine is warmed up

Not 100% sure as to the next best logical step. I doubt it will be injectors as the rarely fail badly and you have two different cylinders. Personally I would probably do a compression test. As I have a tester and it would also eliminate a slipped timing belt.

While the plugs were out to do the test I would compare 1,4 against 2,3. A picture on here sometimes helps

 

[Flat Earth]

Nope, misfires also occur at high revs. In fact, I'd say that it is worst at 2500rpm. Coolant temperature is ok, normally 87ºC, and I have never seen it above 93º. Water pump, tensor and timing belt changed last summer, 10.000km since then. I highly doubt that it is a slipped belt since the misfire started as an intermitent fault that would only happen on very hot days.

I will try to get a compression tester, however it does not feel as a mechanical fault.

Some pics below (new oxygen and MAP sensor, old spark plugs, and readings of the old oxygen sensor).

 

[Flat Earth]

BTW in the first post I said that I've replaced sparks and spark plugs, which makes no sense at all. I was referring to spark plugs and its cables, along with the coilpack. Sorry for the mistake.

 

[koalar]

Here’s my pre CAT and post CAT O2 sensors from a working 69hp

Hot engine

At idle and settled for a minute

 

[koalar]

You can test the timing on these cars without getting your hands dirty

There’s two PID’s

desired timing angle
measured angle

At idle both should be zero, the timing is correct

As you press the accelerator both should go up and match. VVT working correctly

 

[Flat Earth]

You can test the timing on these cars without getting your hands dirty

There’s two PID’s

desired timing angle
measured angle

At idle both should be zero, the timing is correct

As you press the accelerator both should go up and match. VVT working correctly

Hey! Thanks for the oxygen sensor readings. Mine was old so I replaced it, now readings are not weird as long as the fault does not trigger. I am afraid Torque Pro with Fiat EX plugin do not have those PIDs so I cannot check it. I'll try to find them. Thank you!

 

[koalar]

Finding an easy first step isn’t easy

9 times out 10 misfire in hot weather would be the coil pack. I have had two fail exactly like this. Both in a Panda and also in an Alto

Seeing as this has already been changed. It’s unlikely

Are you sure the new coil is okay, was the misfire originally on cylinders 1 and 4 ,


Fuel pump is quite a common failure and is often worse in hot weather. But normally they are worse at higher revs or don’t start

Pressure should be around 50 psi

You might be able to get an idea by reading the injector timing PID a nice running car is around 2-3 and a faulty pump will be over 4.

 

[Flat Earth]

Finding an easy first step isn’t easy

9 times out 10 misfire in hot weather would be the coil pack. I have had two fail exactly like this. Both in a Panda and also in an Alto

Seeing as this has already been changed. It’s unlikely

Are you sure the new coil is okay, was the misfire originally on cylinders 1 and 4 ,


Fuel pump is quite a common failure and is often worse in hot weather. But normally they are worse at higher revs or don’t start

Pressure should be around 50 psi

You might be able to get an idea by reading the injector timing PID a nice running car is around 2-3 and a faulty pump will be over 4.

Yes. DTCs were P0300, P0301 and P0304. I replaced the coil pack (cables included), spark plugs, oxygen and MAP sensors. Faults are still at cylinders 1 and 4. It is easier to trigger the error in the ECU when it's hot outside, however misfires occur at all times (despite that they do not always get logged). The funny thing is that the engine does not have any kind of problem starting, either with cold or warm engine.

Injector timing is oscilating between 3-3.5ms at idle.

Thank you for your time and help

 

[koalar]

Yes. DTCs were P0300, P0301 and P0304. I replaced the coil pack (cables included), spark plugs, oxygen and MAP sensors. Faults are still at cylinders 1 and 4. It is easier to trigger the error in the ECU when it's hot outside, however misfires occur at all times (despite that they do not always get logged). The funny thing is that the engine does not have any kind of problem starting, either with cold or warm engine.

Very unlikely to have two coil packs with the same fault

Injector timing is oscilating between 3-3.5ms at idle.

Thank you for your time and help

Right in the dead zone where we didn’t want it to be and inconclusive

Less and the pressure would probably be okay

Longer and the pressure probably low

We are right in the zone where the fuel trim could be adding extra fuel fuel

This has the same errors and same engine

Intermittent P0300/P0301/P0304 (TL;DR) | FIAT 500 (2007+)

So, we're moving down a bit of a long winding road now - try to keep up... The car is a 2010 Ka 1.2 (yes, I know - it's not a Fiat, but it is). About 2 months ago the car started developing intermittent start-up errors. On the electrical side everything was fine. I decided to order some new...

www.fiatforum.com

 

[09 johno]

This sounds like the broken wire or poor ECU plug connection issue that effects the 1.1. Might be worth carrying out a continuity check between the ECU plug and the coil packs as you have changed everything else I would be looking for a bad/dirty contact or broken wire.

 

[koalar]

This sounds like the broken wire or poor ECU plug connection issue that effects the 1.1. Might be worth carrying out a continuity check between the ECU plug and the coil packs as you have changed everything else I would be looking for a bad/dirty contact or broken wire.

Sorry @09 johno if the following post sound a bit negative.

This is a ECU for a 1.2 69HP (WRO)

And not the 1.1 ECU which had problems (W5Q)

Which would cut out or misfire with a either an injector or coil error code normally while cornering, going over bumps or wiggling the wires

There was never a wiring issue. It was a faulty connector within the ECU.

Once messed with too much, like removing the connector and probing around and you would often need a new/repaired ECU. As per the owner of the original video posted on YouTube

It was far better to cable tie around the connector without ever removing the connector which in most cases fixed the problem permanently

This car fails in hot weather with a misfire code. Which sounds very different to me

Removing the ECU plugs has its dangers. If one of the pins has stuck in its socket and you just pull the cam up it snaps it off. Leading to a very expensive repair. Seen it many times. I have also seen many damaged sockets where the multi meter probe has been jammed in spreading the contacts. Which is why I always leave touching the ECU plugs as a last resort.

I not saying it can’t be the ECU or wiring. But seeing as it sensing everything that is connected correctly it not the same as the standard 1.1 error and I would follow other avenues before messing around the ECU. I would be treating it as a misfire

If I wanted to confirm the 1.1 error I would gently (yes very gently) wiggle the wires by the ECU and see if a misfire could be induced

Sorry again for sounding negative but once you make this particularly fault on the 1.1 worse it leads to a world of pain (cost)

 

[09 johno]

Starting to wonder why I bother answering, just trying to give another avenue of thought, I know very well the 1.1 and 1.2 are different, and know the issue with the 1.1 as i have managed it since owning my Panda. there is no harm in doing continuity checks given that the OP has changed all the ignition parts already.

 

[MrMagoo]

TDC sensor?

 

[koalar]

Starting to wonder why I bother answering, just trying to give another avenue of thought, I know very well the 1.1 and 1.2 are different, and know the issue with the 1.1 as i have managed it since owning my Panda. there is no harm in doing continuity checks given that the OP has changed all the ignition parts already.

Sorry again yes it’s another avenue

The pins on the ECU plug are tiny

It’s very common for them to snap off when you open the cam level to release them

Removing them is the only sensible way to check the wiring

You really need to have done these before to know how much force is require. And keep tapping it back down until it releases

Otherwise can end up with something like this, yes it’s a panda and over £100 repair bill

Same with the 1.1 fault. Starts as an easy repair of cable tie the connect down. Undo the connector a few time and does sometimes end up as a replacement ECU

Most ECU are damaged rather than go faulty

 

[Flat Earth]

Hello everyone,

thanks for all your answers I've been trying to diagnose the issue and I'm not quite sure I've found the problem yet. I checked EVAP system, crankshaft sensor, and I also inspected throttle body and intake manifold (everything seemed fine, even gaskets).

Today, I replaced the ECU with a refurbished one. I got a P0601 that has not reappeared once DTCs were cleared. After doing this procedure to "relearn" the crankshaft sensor position, I took her for a 100-mile drive and I've been unable to reproduce the error. The ECU does not report any DTC at all, however you can sense misfires sometimes (both at idle and also while running). It is true that the ingition is far way better than before, with almost no jerk (even at idle), but it is not 100% fine yet.

I think I'm going to give her a chance for a few days and hope for the better.

Kind of offtopic: I've noticed that the ECU enclosure gets awfully hot, and I think that it might be a good idea to move it to another position (in Fiat 500, it is behind the battery). I'm thinking of building a support of some sort to separate it from the engine, as I'm quite sure such high temperatures are not good for electronic components. I was thinking on using my 3D printer with ABS plastic, but it's crystalisation temperature feels a bit low for the job (105ºC). I found PEEK, which is able to hold up to 140º, but I'm not quite sure that I can print it (it melts at 360-400º, I don't think I can reach those temperatures).

Will report back. Thank you!

 

[koalar]

Did you try a phonic relearn with the old ECU

 

[Flat Earth]

Yes! But with no luck

Did you try a phonic relearn with the old ECU

 

[DaveMcT]

The 100HP has the ECU mounted on the engine and to my knowledge has no problems with engine heat. My guess is the 1.1 fails exactly as Koaler says - the male pins get broken or maybe the female side goes weak. Strapping the connector down hard with zip ties might hold them in contact but doesn't fix faulty pin(s).

A cracked wire in the loom bundle is possible, but broken connector pins are more likely - and much easier to diagnose.

 

[MrMagoo]

What spark plugs are you using?