GDI, decoke, Wurth System Cleaner... help please

[mcbrood]

Hi all,
My 2.4 GDI (4G64) started surging/shunting, particularly on the open road, and the check engine/limp mode was been kicking in periodically (resets OK if I shut off car and restart). Error codes were 77 and 78, which apparently relate to the throttle sensor, but I guessed it may be a gunked up throttle body causing the sensor to get confused. In the weekend I pulled off the throttle body and cleaned about 2-4mm thick of carbon build-up inside it (HEAPS of crud). The inlet manifold obviously had a lot of buildup too, I cleaned the mouth of it up a bit, but obviously it’s pretty dirty inside.
Since doing it the check engine/limp mode hasn’t occurred again (yet??) but the car is still running a bit uneven and surging, particularly on the open road at low revs.

I know I should probably remove the manifold and have it acid bathed, but I’m a total novice and it looks like a fair bit of work. My plan is to try the Wurth ‘system cleaner’ I’ve seen recommended around here for the GDI. Does anyone know a retail outlet (NZ) that stocks it ? Which hose do you squirt it through, and do you detach the hose form the manifold and feed the tube right in, or leave the tube attached and squirt it in through the far end of the tube?

I guess I’ll need to do an oil change or two and do the plugs afterwards? Anyone got any other tips for this? Is it possible this issue is being caused by something different altogether (dirty plugs?).

Any help much appreciated, cheers very much!

[Nick Mann]

It's probably worth checking the plugs, but GDIs are black magic to me, as they seem to be to a lot of people judging by the number of them that don't get properly fixed.

I have seen system cleaners that get squirted through the maf with the car running. I have no idea how effective they would be with the coke build up from a GDI though. I guess the only thing you have to lose is the cost of the can of cleaner?

[MarkSanne]

There are specialized machines / treatments to clean carbon from engines such as these GDI's. These companies often offer on-premise service as I recall (in the UK) so that might be something to investigate? Search 'carbon blast' of something like it on here.

[crazydriver81]

There are specialized machines / treatments to clean carbon from engines such as these GDI's. These companies often offer on-premise service as I recall (in the UK) so that might be something to investigate? Search 'carbon blast' of something like it on here.

Agree with this one. The Carbon Build up will be not cleaned by system cleaner without mechanical treatment. Carbon blasting basically removes carbon with nut shells. No joke!

Further, after cleaning the manifold, you should block the EGR Valve to avoid this happening in Future.

[swinks]

Problems with GDI engines are quite known and notorious in Polish Galant community. So all you described is nothing new.
Basically...
- 1st you need to remove intake manifold and clean one from carbon deposits. Simple throttle body cleaners in spray, some water with soap and bottle brush will do magic trick.
- 2nd, your throttle body suffers from typical failure for GDI ones (judgeing from description), it's magnet came off in electronic tps unit. GDI throttle bodies are electronically driven unlike other classic mechanical one. I know that few chaps in Poland do refurb of those TB for nuts (i.e. few pints of lager).
- 3rd, it's not unwise to check performance of high pressure fuel pump, seems that with age those pumps use to give in, and tired one will give you rough ride on steady cruise.

[chris g]

Is this the engine where an 'Italian tune-up' has been recommended...?