Technical 1.2 16v misfire

[Geborga]

I bought a car that didn't run, due to low compression on cylinders no. 2 and 3. Fixed it, had a head gasket issue. Compression is 13.8bar on all 4 cylinders. Timing is correct, set with the special tools for this engine (piston 1 on its way down, with all 4 cylinders at mid-stroke, and with both cams locked).
I installed a couple of things, namely: new plugs, leads(copper core, silicone insulation), both coils, fuel pump, throttle position sensor, crank angle sensor, MAP sensor, coolant temp sensor for the ECU.
And I checked a couple of things: compression, as mentioned above, the earthing point beside the ECU, idle vacuum in intake manifold, cleaned the injectors and fuel pressure regulator (they are not clogged), exhaust isn't clogged, and the air filter isn't super dirty. Tried disconnecting the o2 sensor, still no good. Tried driving it with the gas cap off, to rule out purge valve issues.
It gets worse under load, and sometimes it stalls, or won't even start. Sometimes, it backfires, the idle is very uneven, and it only starts with the throttle slightly pressed.
What else should I look for? Bad ECU? Something with the crank signal pulley? Fuel filter?(bought one, couldn't change it beacause the connectors are broken... Thinking of cutting them off, and installing the new one with hose clamps) An earthing point?

 

[Chris parry]

1.Have you got the spark plugs leads mixed up when you changed them?
2. Have you checked you have spark getting to all the plugs? (pull each one off one at a time and see how it affects the running)

 

[Geborga]

Yes, i tried it, and they are not mixed up. Normally, on idle all 4 cylinders are running, but sometimes under load, when driving it drops 2 or all 4 cylinders.

 

[Chris parry]

Fuel problem?? are you using good fresh fuel or is it old stuff in the tank? if the fuel is good maybe your initial thought of fuel filter might be right..
You say compression is good, you have spark (at least when not under load) so only thing that changes under load is more fuel needed

 

[Geborga]

I didn't drain the tank, because it had so little fuel in it, so filled up with about 20 litres of fresh 100 octane.

 

[PuntoHowTo]

Do you know which cylinder is missing ? An easy way to check is to pull the HT leads one by one till you find the mis

You can then check for a spark in that cylinder, these use a common rail so if the other cylinders are getting fuel then the only issue fuel wise would be the injector.

You can check this by turning the car over with the injectors sat in clear plastic bottles, turn it over for an extended period and that will tell you it one injector is giving less fuel than the others.


These are some of the things you can try

 

[Geborga]

Do you know which cylinder is missing ? An easy way to check is to pull the HT leads one by one till you find the mis

You can then check for a spark in that cylinder, these use a common rail so if the other cylinders are getting fuel then the only issue fuel wise would be the injector.

You can check this by turning the car over with the injectors sat in clear plastic bottles, turn it over for an extended period and that will tell you it one injector is giving less fuel than the others.


These are some of the things you can try

I tried this as well, and the amount of fuel was about the same in all four small trays.