Fabia 1.4 mpi cold misfire

[Gareth Storey]

Hi there. My missus has a 2002 1.4 mpi which over the last week has developed a misfire when cold but if left to fully warm up it runs perfect. I have changed the plugs and checked and cleaned all the breather and vacum pipes but there has been no change. The ecu logs a code for a misfire on cyl 2 so at Least i know where the problem lies. I also have a almost new coil pack on its way as a mate had one lying in his garage. Any ideas where the problem could lie? Im thinking that if i get the coil pack and its still the same then the issue may lie with the injector. Thanks for reading 

[sepulchrave]

More like to be the coolant temperature sensor than anything else.

[YS53]

I guess the coil pack is a good starting point Gareth and perhaps plug leads ?

But as Sep posted above the CTS might be a possibility although I would have thought you might get a separate fault code for that ?

[YS53]

Just checked back on my records for our 2002 Polo 1.4 16v which I did a little pre MOT work on last year.

I had P0118 (CTS low temp) and the possibly related  P1151 (long term fuel trim) - it was the original CTS still on the car so I splashed out on a genuine VW CTS (£40 i think) 

[Gareth Storey]

The only code it has been logging is 16686 - cyl 2 misfire. The complete thermostat housing and cts was replaced last year and it hasnt skipped a beat until a week ago. Its the engine that runs a wasted spark with 1 complete coil pack across all 4 cylinders and no ht leads.  I understand that the cts does effect the engine but why would a dodgey cts only effect cyl 2 and not the rest 

Edited 10 April, 2017 by Gareth Storey

[sepulchrave]

It could affect one cylinder if it's borderline too lean, however if it was replaced last year then it probably isn't that, whip the spark plug out of cylinder 2 and take a look at it, it may be worn, if so replace all 4.

[Breezy_Pete]

If the coilpack doesn't fix it, try moving the injector for cyl 2 to somewhere else and see if the fault follows. If it doesn't, try compression testing to see if cyl 2 is an odd one out.

[badgerdisco]

I have the same problem at the moment on my newly purchased Mk1 Fabia - I have purchased a new temperature sensor and am fitting tonight. Did you ever conclude what the issue was, Gareth?

Thanks!

[Gareth Storey]

3 hours ago, badgerdisco said:

I have the same problem at the moment on my newly purchased Mk1 Fabia - I have purchased a new temperature sensor and am fitting tonight. Did you ever conclude what the issue was, Gareth?

Thanks!

 

No mate. So far ive changed the plugs, coil pack and have swapped the inectors around. I also removed the throttle body and map sensor and cleaned them bit its still logging a cyl 2 misfire. Let me know how you go with the cts please as im at my wits end haha

[badgerdisco]

I also changed the plugs but that didn't change things - unfortunately the temp sensor was the wrong part... even though I put my reg into Euro Car Parts. I'll try again this weekend hopefully. Do you happen to know which part it is? 

 

My worry is that it might be an early sign that the head gasket is failing. Mine loses a bit of coolant each month and the problem goes away when hot (i.e after expansion)...

 

[YS53]

4 hours ago, badgerdisco said:

 

 

My worry is that it might be an early sign that the head gasket is failing. Mine loses a bit of coolant each month and the problem goes away when hot (i.e after expansion)...

 

Have you had a look at the radiator temp sensor ?mounted low down on the nearside of the rad - they are infamous for leaking,I tightened mine up by no more than 1/16th of a turn (ie a gnats kok) and solved my slight coolant loss (there was heavy staining around the temp sensor).

Caution do not tighten very far - it is screwed into plastic !

Edited 11 May, 2017 by YS53

[badgerdisco]

9 minutes ago, YS53 said:

Have you had a look at the radiator temp sensor ?mounted low down on the nearside of the rad - they are infamous for leaking,I tightened mine up by no more than 1/16th of a turn (ie a gnats kok) and solved my slight coolant loss (there was heavy staining around the temp sensor).

Caution do not tighten very far - it is screwed into plastic !

 

Thanks a lot for the helpful suggestion. I'll have a look; I don't suppose you have an image of the part? I had a look on google but it's just the coolant sensor that keeps popping up. 

[YS53]

1 hour ago, badgerdisco said:

 

Thanks a lot for the helpful suggestion. I'll have a look; I don't suppose you have an image of the part? I had a look on google but it's just the coolant sensor that keeps popping up. 

Sorry I do not have an image.

If you look down the back of the radiator (on rear) - about 1/2 way down (on the near side on a polo - yours should be similar) there should be hex headed largeish switch with a couple of wires connected (from memory approx 29-30mm spanner)- I was lucky in that I had a cut down short spanner which I could get onto it - but I only gave it a slight tweak as it would be too easy to strip the plastic thread.

[Breezy_Pete]

29mm spanner. There's a brass threaded insert in the plastic.

Edited 11 May, 2017 by Wino

[YS53]

Thanks Wino - didn't know about the brass insert but ( as I am sure you are well aware) - still should only be tightened the absolute minimum as it is very easy to put excess torque on with a 29mm spanner.As I said - I was lucky and had a very short cut down spanner to give the thing a wee tweak : )

[Breezy_Pete]

I seem to remember that 30 Nm is the recommended torque. For both our cars that was about a 20 degree tightening tweak . A deep socket will just get on it with the loom connector unplugged, then you can use a torque wrench if you want to be safe. 

[YS53]

I did mine the high tech way - found an old open ended cut down spanner which had languished in my 'odds n sods' tool box for years so I did not have to disconnect plug  and then just gently tweaked it until I chickened out LOL been ok since 

Edited 11 May, 2017 by YS53

[badgerdisco]

On 10/05/2017 at 19:30, Gareth Storey said:

 

No mate. So far ive changed the plugs, coil pack and have swapped the inectors around. I also removed the throttle body and map sensor and cleaned them bit its still logging a cyl 2 misfire. Let me know how you go with the cts please as im at my wits end haha

Hi Gareth,

 

Replaced mine today - if I wasn't me I'd have laughed very hard as I received a face full of coolant! ha! Anyway, it has improved the car running cold but there's still a hesitation in 2nd and 3rd gears. I'm not sure I'm going to bother investigating further as it's generally running ok and fuel economy is reasonable. What will you do now?

[badgerdisco]

17 hours ago, Wino said:

29mm spanner. There's a brass threaded insert in the plastic.

 

Thanks a lot everyone for your help. I'm struggling still, despite the excellent photo (I'm really not great at this kind of thing!!) - if it's on the side closest to the battery then there's little room to see or do anything! However, I took a photo of what I can see, and can't really match it up to your photo. Ignore the damp, I replaced the coolant sensor earlier and... let's just say I lost some coolant... and pride ; )

[Breezy_Pete]

Yep, battery side. May be better coming up from below, access-wise. 

[YS53]

Between the radiator and the engine (ie the rear side of the radiator) - if you look down with a good LED torch you will see it.

Edited 12 May, 2017 by YS53

[badgerdisco]

I'm pleased to say that the temp sensor was at fault and, although I didn't notice initially, the hesitation has gone. Thanks to this forum an easy solution and £12 for a part. 

 

Have also tightened the radiator (a tiny amount!) - cheers everyone!  

[badgerdisco]

Thanks Wino - did this at the weekend, it did tighten a tiny amount! So fingers crossed! Access was not easy at all... as usual : )

[Gareth Storey]

Well i still havent got it fully sorted.. Replaced the coolant temp sensor just incase the pattern one that came with the thermo housing was duff and that made no difference. Got my hands on a map sensor and switched it out and that made no difference. Ive even gone as far as changing out the fuel pump as tge symtoms it was giving pointed towards a failing pump. Has my head melted now tbh. When you first start the engine it runs rough for about 5/10 seconds then settles which tbh we could live with. The problem is that it when being driven it sometimes hesitates and if you accelerate hard from a stop or when filtering it can bog then hesitate before it goes but if you apply the throttle gently it doesn't do it. 

[sepulchrave]

2 minutes ago, Gareth Storey said:

Well i still havent got it fully sorted.. Replaced the coolant temp sensor just incase the pattern one that came with the thermo housing was duff and that made no difference. Got my hands on a map sensor and switched it out and that made no difference. Ive even gone as far as changing out the fuel pump as tge symtoms it was giving pointed towards a failing pump. Has my head melted now tbh. When you first start the engine it runs rough for about 5/10 seconds then settles which tbh we could live with. The problem is that it when being driven it sometimes hesitates and if you accelerate hard from a stop or when filtering it can bog then hesitate before it goes but if you apply the throttle gently it doesn't do it. 

 

It definitely sounds like an unmetered air leak when you put it like that, either vacuum pipe or inlet plenum somewhere.