Rough Idle - P2008

Hi,

 

I have been troubleshooting a rough idle for a little while as well as some intermittent codes. The intermittent code is P203 (cylinder 3). I have datalogged and there is some roughness in cylinder 3 from time to time but its not bad. Have had it in to subaru shop and had the spark plugs changed. They can't really find anything else wrong.

 

The CEL is on for a cyle or two but then goes off. Finally last night another code popped up, P2008 which is TGV intake manifold runner 1 circuit open.

 

I can't find a tonne of information on TGVs, but they appear to be important at low RPM and idle so I wonder if maybe this might be the source of my problem.

 

Just curious exactly what a TGV does, whether it can cause a rough idle; and what to do about it. The forum and google searches don't turn up much except tutorials on how to remove and delete them.

 

So, could this be my problem and what do I do to fix? Is there a good troubleshooting doc on TGVs?

The FSM is the place to start for troubleshooting the P2008. Since you haven't mentioned what car you have, I can't link you directly to yours, but this will get you there.

http://legacygt.com/forums/showpost.php?p=4487789&postcount=359

Basically, you just make sure the harness & connector are OK, and if they are, you replace the TGV motor.

Good used TGV motors are like $20 on eBay, not worth agonizing over firing the parts cannon.

 

Edit: just noticed your spelling of "tonne", which suggests to me you may speak funny. In that case, please note the FSMs above are for USDM cars and will not be 100% accurate for your car.

 

Regarding the misfires,

1. P203 is not a code, did you mean P0303?

2. Just replacing all the plugs is not how you diagnose a single-cylinder misfire. I'd be curious to know exactly what the shop did, but the broad strokes are swap the #1 and #3 coils and see if the misfire follows. If not, typically one would swap plugs next, but since yours are already replaced, the next step would be to swap injectors.

 

I personally have no experience of TGVs causing misfires; others may have more to contribute on that score than I.

Thanks,

 

In Canada, thats how we also spell tonne but I don't speak too funny.

 

Car is a 2005 legacy gt. Swapped the coils and the misfire didn't follow.

 

Shop was the dealer. Not Surprisingly, they are never any help when I bring the car there. They are happy to change the oil though.

Yeah, dealer monkeys know fnek-all about troubleshooting. You're much better off finding a good indy shop. Anyway, on to swap injectors, and if that doesn't do it, compression test.

Ya, swap injectors is the next step, however this TGV code really makes me question whether that might be the problem right there. Hoping for someone to provide some insight there.

Ya, swap injectors is the next step, however this TGV code really makes me question whether that might be the problem right there. Hoping for someone to provide some insight there.

 

TGVs are mechanically synchronized for the cylinders on the same side so what it can be is either the donut gasket issue or that you have to adjust the valve clearance. A compression test may not reveal that the valve clearance is bad - which is a good sign since then you are in an early stage where it may be enough to adjust the clearance without removing the heads.

OK, I think a smoke test has shown a leak coming out of the cylinder 3 TGV and when removing it I can see the shaft seal/gasket leaking.

 

I can't find this part in any of the diagrams? Is this the donut gasket issue you speak of?

If it's the gasket between manifold and tgv - then it's the donut gasket. Just visit a dealer and explain what gasket you need. Replace all of them, not just the one that's leaking. If you work on the tgvs you need them anyway.

 

But you refer to the shaft seal, that's a tricky one and may mean other tgv problems like it's not opening/closing correctly. You may want to get a new tgv from a donor engine, and considering that blown engines happens it shouldn't be too hard to find a whole set cheap.

I think I should note that this is the side that is by the turbo, not the side with the actuator on it.

Update:

The car motor was removed and everything put back together, zip tied etc. Smoke test reveals no leaks. The trims look fine.

 

 

 

Still having intermittent #3 misfires and rough idle.

 

 

Took car to a tuner. They believe it is fuel problem (they did leakdown, smoke test, swapped coils and injectors). Misfire did not follow the coils or injectors.

 

 

They have indicated that either my fuel pump is weak, the fuel filter is partially plugged or my injectors need servicing or replacement. They are not sure which. The injectors may be delivering poorly in multiple cylinders without misfire.

 

 

Is there anything else I can do to narrow down? Trying to limit the money I pour down the drain here.

Not sure if this will help since I got this code as well it points to the tgv sensor (tps) that’s on the passenger side rear in front of the turbo in the case of mine my turbo is right on the sensor and sometimes I get a CEL for it and sometimes not.. one day it was bad enough to put me in limp mode.

Did you fix it or just let it go away. I haven't got this code for several months. Its just P0303 now.

 

 

Is it possible for a weak fuel pump to only cause misfires in cylinder 3? Is this the farthest from the source and the most likely to have bad pressure?

I replaced the sensor