Engine missing

hi I have a 2004 c3 1.1 and it started missing a week ago, I changed the coil as it was showing random miss fire. This didn't cure so I had a look online and the other item was the map sensor, so I changed that and again no joy. I then called the AA out and they said it was an injector. So yes I changed all four injectors and again no joy still missing and about £120 worse off. Can anyone advise

Colparr03 wrote:hi I have a 2004 c3 1.1 and it started missing a week ago, I changed the coil as it was showing random miss fire. This didn't cure so I had a look online and the other item was the map sensor, so I changed that and again no joy. I then called the AA out and they said it was an injector. So yes I changed all four injectors and again no joy still missing and about £120 worse off. Can anyone advise

I would have checked the plugs before changing the coil pack, but its worth doing them both if either are bad.

Its advisable to hook up a OBD code reader (from here on ebay) to get an idea of the problem, it will help with, for example, differentiating between MAP and ignition parts faults.

Hi
Yes changed the plugs with the coil mate and have a code reader but the engine management light isn't on so no codes, I think that's why the AA went for injectors

Colparr03 wrote:no codes

No codes and poor running engine could indicate bad valve, unmetered air intake or some mechanical, non monitored issue.

Thanks for the info, car was running fine until I had to bump start it as the battery went flat, what do you mean my unmetered air intake, is that what the map sensor measures as I've changed that ??

Colparr03 wrote:what do you mean my unmetered air intake

Air getting into the fuel mix that the ECU doesn't know about. Can cause poor running in open loop O2 mode.

The MAP sensor monitors the air intake, so if the MAP is bad or air is getting in somewhere avoiding the MAP then that's unmetered air.

Colparr03 wrote:car was running fine until I had to bump start it as the battery went flat

Did you get to the bottom of the reason for the flat battery?

I suppose you should start with all the basics on the battery/charging system before getting too deep...

Make sure battery terminals are clean and tight etc.

Hi
Battery was flat due to lack of use, the car only gets used every now and then. I've had the inlet manifold off and can't see anything wrong with it so don't think it's leaking air in anywhere. While it was off I done a compression test and they were. No 1 200psi, no2 125psi, no3 200psi, no4 200psi. Not sure if the low compression on 2 is low enough to cause the Miss fire ??

Update guys, heads off and no2 exhaust valve isn't sealing so new exhaust valve it is. But it looks like its had a timing belt problem in the past and looks like all 4 exhaust valves have hit the pistons at some point in its life

Colparr03 wrote:Update guys, heads off and no2 exhaust valve isn't sealing so new exhaust valve it is. But it looks like its had a timing belt problem in the past and looks like all 4 exhaust valves have hit the pistons at some point in its life

Thanks for the update.

Colparr03 wrote:Hi
Battery was flat due to lack of use, the car only gets used every now and then. I've had the inlet manifold off and can't see anything wrong with it so don't think it's leaking air in anywhere. While it was off I done a compression test and they were. No 1 200psi, no2 125psi, no3 200psi, no4 200psi. Not sure if the low compression on 2 is low enough to cause the Miss fire ??

A variance between any 2 readings shows a problem...

Great work tracking down the problem


If you don't change all the valves, it may be worth re-lapping them all. The head will only come off one a lifetime of the engine, so its worth spending that little extra time

Yeah will do, to be honest the valves are not expensive so will probably change the all what do you think of the marks off the exhaust valves on the pistons from a past problem