Tearing Hair Out Over My Polo 1.2 3cyl

[BigGordie34]

Hi everyone, i'm at the end of my tether with my girlfriends polo. Its 2003 1.2 E 3cyl 55ps that we've had from a year old. It went for its first Mot in december which it passed but garage said it was running rich and the coil packs were probably knackered. It had been running rough for a while but being a 4cyl golf driver, i had put this down to it only havin 3. Replaced coil packs myself(all 3) still no better.Emissions light came on next so took it back to garage and they said no3 coil pack is knackered again. So i replaced this and still no better.At idle the engine coughs and splutters and shakes on its engine mounts, also seems to have a flat spot around 3000revs.Emission light has now gone out so i'm totally confused. Anyone help?

[Col]

You need to read it / get it read for faults.

Look in the vagcom thread, see link in my sig.

My guess though would be a dodgy lamda if you've done the coil packs.

[Flash2]

Get it read for faults and I can tell you right now what it's going to say...Cyl 3 misfire. That's why the garage told you the cyl 3 coil had gone down again. If replacing the coils hasn't fixed the problem then it could be a problem with the fuel injector. You could try changing the injector in cyl 3 with one of the others and see if the misfire moves to the cylinder where you fitted it. To change the injectors, remove the engine cover. You should see the fuel supply rail running across the top of the engine. It's a black pipe with what looks like a tyre valve at the right hand end. The fuel rail is secured to the engine by 2 allen bolts. Undo the two bolts and lift the fuel rail off the engine. The injectors are secured to the fuel rail with clips. Lever the clip off, disconnect the wiring plug and pull the injector off the fuel rail (some fuel will leak out when the injector is removed - have a rag handy). Make sure your injectors have a rubber 'O' ring at each end. Sometimes the 'O' rings stay in the fuel rail/engine when you pull them out. And make sure the ignition is switched off while disconnecting any wiring or fault codes unrelated to your problem will be recorded in the engine ECU.

Regards - Jim.

[BigGordie34]

Thanks for your help but unfortunately it still is not sorted. I've swapped the injectors over but problem stayed with no3 cylinder. I can take the plug off the coil pack and the injector on no3 and it makes no difference to how its running. I'm now wondering lambda sensor or ecu/wiring problem. So the quest goes on........Any more ideas would be gratefully appreciated.

[Flash2]

The only other thing I've heard of that is sort of semi common is that there can be poor connections on the multiplug that connects to the coil packs. I've never come across that myself, so I'm not exactly sure what to look for.
I'd remove the plug from No. 3 coil and check that none of the connector pins have unlatched and backed into the connector. Also compare the pins in the connector with those in the other two. Make sure the pins all look the same, i.e. none of them has a wider gap than the others. I take it that you have removed the spark plug and checked the gap? Have you plugged a spark plug into No 3 coil to see if it is producing a spark?
If you don't see any thing wrong, then perhaps the fault is internal within the engine. I'd carry out a compression test or even better a leak down test to make sure the problem isn't sticking valves, etc.

Jim.