Technical Brava miss fire.

[Big Chris]

Hi all

I have a 2001 1.2 brava 80sx. It's been a good little runner up until recently.
The car started to miss fire under load about a month ago ( engine management light flashing, then staying on ) so I did some research and replaced the coil , ht leads and plugs and it ran spot on until now.

It's started misfiring again!!!!

So I replaced the air filter hoping this was the problem but hasn't cured it.

I had the diagnostics read and it came back with miss fire cylinder 4 and engine temp circuit 1 malfunction. The guy who did the diagnostics said if the car starts in a morning ( which it does ) it couldn't be the engine temp sensor and it could be the ecu?

The miss fire on cylinder 4 couldn't be down to the coil, leads and plugs as they are new??

Another weird thing is the key code light comes on every now and again but the car starts and runs??

Also the air duct from the air filter to the throttle body is torn but I've taped it up.
Could this cause miss fire under load?

I've also cleaned as many electrical connections as I could find!!

Any help or suggestions would be very helpful. I feel like scrapping it at the minute!!!!

 

[Most Easterly Pandas]

cylinder 4 couldn't be down to the coil, leads and plugs as they are new??

It could be as although new they could still be fault. Was it the same cylinder before replacing them

 

[Big Chris]

I'm not sure which cylinders were missing before. I just replaced both the coil and leads and hoped it would cure the problem which it did briefly.

I will check the new leads with a multimeter. Has anybody any idea what the resistance on the leads should be?

 

[Most Easterly Pandas]

A multi meter won't tell you if they're arcing. Have you the originals still

 

[Big Chris]

No.. I binned them ???

Do you think the new leads may be duff?

 

[Most Easterly Pandas]

No.. I binned them ???

Do you think the new leads may be duff?

As I've said, not an impossibility. Never throw away old parts until everything is running fine ideally. Can you salvage them from the bin?

 

[Big Chris]

No, they were binned weeks ago. ?

 

[Adrian Bravo]

Ive read in the past a couple of people fitting new leads and they where duff/rubbish.

 

[Big Chris]

Right.. Bloody thing drives fine now, but ticks over really rough and there's a strong petrol smell?? any thoughts?

 

[m20b25]

Test either of the lambda sensors?

 

[Big Chris]

Test either of the lambda sensors?

How would I test them?

 

[Big Chris]

Here's an update.

I removed the TB and cleaned it out ( it was filthy ) and the car idles fine now.

Driving, the car is now miss firing again ( especially after over run ) and is using a LOT more fuel than it did.

It also kicked a load of this out of the exhaust ( see picture )

Thank you for all your inputs and advice.

 

[Adrian Bravo]

Hey Chris,

Has the engine management light come on since you had it rest? Reading your posts im leaning towards somekind of overfueling. I think since its using a noticable ammount of fuel then it would be good to concentrate on things that would cause it to overfuel. Maybe injector in cyliner 4 is sticking open since the first diagnostic brought cylinder 4 up previously? Lambda sensors? Is the knock sensor connected to the block securely? There is a MAP sesnor on top of the passenger strut tower it has a small air pipe going into it and a electrical connector block (item 30 on the pic bellow).

Have a look at the spark plug colours that could indicate how the cylinders are burning.

I dont know from my level of experience if the soot from your exhaust is a sign of something terminal or just because of overfueling.

Here is a test for the injectors themselves.

I know you have a new coil pack but heres the test for that aswell;



And heres a image listing the 1242 ignition system components.


Good luck, keep plugging away at it.

Here's an update.

I removed the TB and cleaned it out ( it was filthy ) and the car idles fine now.

Driving, the car is now miss firing again ( especially after over run ) and is using a LOT more fuel than it did.

It also kicked a load of this out of the exhaust ( see picture )

Thank you for all your inputs and advice.

View attachment 116996

 

[Big Chris]

Thanks for the reply Adrian, I'm going to check what you have suggested later today. Ill let you know what I find. I hope I can sort it soon. I feel like getting shut if it lately!!! :-/

 

[Big Chris]

Hi all

Injectors checked out fine, coil fine, engine light still on ( ordered a scanner to check what it's saying ) map sensor unplugged and connector cleaned up. ( no air pipe to it though? ) checked the fuel pump and seems to be working fine ( unplugging it makes the car stop when the juice runs out ).

I'm not sure how to check the lambda senders?

In desperation I put some new ht leads on it and it hasn't miss fired since but.... Engine light still on and it's down on power.

I hate fiats at the minute. ?

 

[Big Chris]

Oh... And where is the knock senser on my car? I couldn't find it??

 

[Adrian Bravo]

This page shows the MAP on the left end of the intake manifold part 30.

Heres another test for the MAP sensor. I should have linked it the otherday but was in a rush.

Hi all

Injectors checked out fine, coil fine, engine light still on ( ordered a scanner to check what it's saying ) map sensor unplugged and connector cleaned up. ( no air pipe to it though? ) checked the fuel pump and seems to be working fine ( unplugging it makes the car stop when the juice runs out ).

I'm not sure how to check the lambda senders?

In desperation I put some new ht leads on it and it hasn't miss fired since but.... Engine light still on and it's down on power.

I hate fiats at the minute. ?