Intermittent EPC, Traction Control and Limp Mode

[liam]

I'm having an intermittent problem with my 2005 Golf GTI AXX ENGINE.
Every now and again (sometimes on start up, other times when I go to pull away) the car will go into limp mode and it doesn't feel like the turbo is working. Other times it will do the same but the EPC light will come on and it sounds like it's misfiring.
Had it scanned with VCDS, Error P0123.
Trusted VW specialist had it, tried replacing throttle body, sorted a few problems with the wiring loom and Tried a different ECU and it sorted it, they took a look at mine and all the contacts corroded so a bunch of those were replaced it sorted it for a few days but then it started happening again. 

Getting frustrating now as I haven't been able to drive my car for about 2 months, any other ideas?

Thanks

[AJP]

Have you checked the basics - plugs and coils?

[liam]

Have you checked the basics - plugs and coils?

Thanks for the response
I assumed they would have checked, but if it was those wouldn't it be constant? And would it throw the EPC light?

[AJP]

Have you checked the basics - plugs and coils?

Thanks for the response
I assumed they would have checked, but if it was those wouldn't it be constant? And would it throw the EPC light?

You can have all sorts of misfires without a light coming on or a fault code being stored.

If you do get a misfire code on a specific cylinder, swap the plug on that cylinder with one of the other plugs, clear codes, see if it misfires again and stores a code on the cylinder you moved the plug to. If it does, it's a bad plug. If not, do the same thing with the coils.

This is all assuming it's actually a misfire. If it is, and your plugs and coils are ok, it might be an injector. If not, you could do with getting some data logging done with VCDS.

Could be any number of things. But it's worth troubleshooting the easy bits first.