[harms]

Forgot to mention; today I noticed an oil leak while I had the bottom cover off. A moderate amount of oil is leaking/blowing down onto the waterpump, seemingly from where the plastic turbo inlet connects to the front turbo although I'm not 100% sure that is the source. It doesn't look like its coming from the VCG.

It also dawned on me that the oscillation issue doesn't occur when the car is cold. Once it starts to warm up (< 5 mins driving) then the issue starts.

Is this a clue? Or just an unrelated problem?

[e36mmm]

have you thought of the valve adjustment? I would check vacuum lines, both solenoids for exhaust and intake.. and also reset throttle adaptations like socket has mentioned. Too many electronics in these cars and I hate it but I love the car Hope you find a resolution soon. Also...
If you have a surging problem, and I have had that problem, check intercooler piping for dramatic leaks, slow leaks are normal, the vanos soleniods as there are two of them, one for exhaust and one for intake should be replaced in my opinion if they have not been replaced before. Finally vacuum lines should be replaced as they got hot in the engine bay and when they become brittle, can cause surging. Have you taken it to active? They fixed my surging problem within a day.

[vtl]

Could be that once the car warms up it goes from open loop into closed loop and thats when you get issues.

Only thing I can think of is an exhaust leak between the downpipe and the turbo or an intake manifold leak. Leaks here can cause the afrs to stuff up, but then you would expect a dodgy idle or under load.

[harms]

Originally Posted by vtl

Could be that once the car warms up it goes from open loop into closed loop and thats when you get issues.

Only thing I can think of is an exhaust leak between the downpipe and the turbo or an intake manifold leak. Leaks here can cause the afrs to stuff up, but then you would expect a dodgy idle or under load.

I sometimes get an idle stumble when cold, but tbh my idle is pretty good, and under any load (light or hard) the car goes fine, and under decel its also fine.

Do you know how the rear o2 sensors work? I think they just indicate a lean/rich/stoich value while running in closed loop, so I wonder if they are the problem...

Also, what are your thoughts on the plausibility of clogged secondary cats being a cause?

I'm really running out of ideas.

[Socket]

Is this still causing you grief mate?

[harms]

Originally Posted by Socket

Is this still causing you grief mate?

Yeh mate. I really have no clue what is wrong with it.
I might have to take it to Active.

[DR-JEKL]

Whoever told yu to replace O2 sensors if a fool!

Haha but seriously I believe due to the age of the vehicle its good to swap them out as they wear over time, especially more so in a turbo vehicle!

Vanos solenoids... Maybe see if a fellow member who has a fresh set is happy to loan/swap their solenoids into your car and go for a blap to see if it improves things?

[vtl]

Originally Posted by harms

I sometimes get an idle stumble when cold, but tbh my idle is pretty good, and under any load (light or hard) the car goes fine, and under decel its also fine.

Do you know how the rear o2 sensors work? I think they just indicate a lean/rich/stoich value while running in closed loop, so I wonder if they are the problem...

Also, what are your thoughts on the plausibility of clogged secondary cats being a cause?

I'm really running out of ideas.

Clogged secondary cats would cause a lot of power loss so thats unlikely

Rear o2 sensors are normal, non-wideband sensors so yeah that's how they should work. In theory they're only there for measuring cat efficiency but I have read people fixing rough running issues by replacing them. Can you run the car with the rear o2s unplugged?

[harms]

Originally Posted by vtl

Clogged secondary cats would cause a lot of power loss so thats unlikely

Rear o2 sensors are normal, non-wideband sensors so yeah that's how they should work. In theory they're only there for measuring cat efficiency but I have read people fixing rough running issues by replacing them. Can you run the car with the rear o2s unplugged?

Hmm i might try unplugging them and see what happens. Good idea.

[Scotty89]

I still think it's vacuum related somehow.

Have you tried some sort of leak down test on the intake manifold and charge pipe?

[harms]

So I unplugged the post cat o2 sensors to see what would happen.
I still have the issue unfortunately, after it warms up of course.

The car actually drove fine and a CEL didn't even pop up until I turned off and on again so I guess these sensors don't do much! haha

Cold start and idle with rear o2 sensors plugged in:
http://datazap.me/u/harms/logs-no-re...-23&zoom=0-332

What is really interesting is the large discrepancy in LTFT's, with bank 1 being much more negative, which could indicate a leak somewhere perhaps?? I hadn't been logging both LTFT banks before so hadn't noticed this.


Driving after warmed up with post cat o2 sensors unplugged:
http://datazap.me/u/harms/logs-no-re...23&zoom=79-322

http://datazap.me/u/harms/no-rear-o2...3&zoom=124-402

The STFT's are much more positive with less of a swing to negative like before. Difference in LTFT's is still there just not a pronounced as at idle.

So does anyone else think I should be looking for leaks (perhaps exhaust) on bank1? Coincidentally the front turbo is the one which looks to be leaking oil from the inlet...

[vtl]

Yeah could be the downpipe->turbo gasket, any gas that leaks won't be metered properly by the sensors. I think most people don't replace that gasket when they go catless, they normally replace the downpipe->exhaust gasket only.

Just curious, did you remove your o2 sensors without dropping or lossening the downpipes? Hypothetically if you had a leak before surely it would only get get worse if you played with the clamps

[harms]

Originally Posted by vtl

Yeah could be the downpipe->turbo gasket, any gas that leaks won't be metered properly by the sensors. I think most people don't replace that gasket when they go catless, they normally replace the downpipe->exhaust gasket only.

Just curious, did you remove your o2 sensors without dropping or lossening the downpipes? Hypothetically if you had a leak before surely it would only get get worse if you played with the clamps

Yeh I didn't replace those gaskets.

I changed O2 sensors without dropping the DPs. The clamps looked nice and tight so nothing obviously wrong. This problem has been gradually getting worse over months and months so a gasket would make sense.

[Scotty89]

...I don't think there were any gaskets in mine. Which ones are you talking about?
Is there supposed to be a gasket under the V band clamps to the turbos?

[vtl]

Yes it's part number 18307553601

[Robsvictims]

Any luck with this issue yet?

[Socket]

Update please Harmsy

[harms]

Update:

I took the car to Active to inspect the turbos and look at the issue.

Turbo's are fine. Very minimal shaft play. No oil leaking into the exhaust.
The abnormal amount of oil is coming down through both turbo inlets.

I asked them to replace the turbo > DP gaskets while the DP's were out even though they didn't think that would be the problem.

Jin also found the rear inlet wasn't connected very well, and upon fiddling with it, the inlet crumbled!

So I took down the VTT inlets I luckily had sitting there, which i wasn't planning on installing until sorting this shit out. So now I have the VTT inlets installed at least.

Jin replaced the PCV Vent hose hoping this might be the problem.

None of these things worked. Still have the issue.

I've been doing a bit of research on how the PCV system works, and there is a check valve integrated into the valve cover, that in vaccum is open and in boost is closed. I think it's plausible that this valve is clogged and not working effectively causing crankcase pressure to vary during vacuum and the car is compensating with STFT's. Or maybe not i dunno.

So, next I'm thinking of replacing the valve cover.

I'll have a bloody new car soon!!

[MJ80.]

Wedge was rambling about some oscillating throttle issue recently in the mhd thread, i don't believe it was mhd exclusive and it related to race logic if i remember correctly, given you have been looking at everything so far, id have a flick through those last few pages in the mhd thread and see if its relevant.

[harms]

Originally Posted by MJ80.

Wedge was rambling about some oscillating throttle issue recently in the mhd thread, i don't believe it was mhd exclusive and it related to race logic if i remember correctly, given you have been looking at everything so far, id have a flick through those last few pages in the mhd thread and see if its relevant.

I think i found what you're referring to:
http://www.e90post.com/forums/showpo...postcount=3020

The difference here is that that when I flash completely back to stock I still have the oscillations. It's got to be a hardware/mechanical problem...

[Socket]

Originally Posted by harms

Update:

I took the car to Active to inspect the turbos and look at the issue.

Turbo's are fine. Very minimal shaft play. No oil leaking into the exhaust.
The abnormal amount of oil is coming down through both turbo inlets.

I asked them to replace the turbo > DP gaskets while the DP's were out even though they didn't think that would be the problem.

Jin also found the rear inlet wasn't connected very well, and upon fiddling with it, the inlet crumbled!

So I took down the VTT inlets I luckily had sitting there, which i wasn't planning on installing until sorting this shit out. So now I have the VTT inlets installed at least.

Jin replaced the PCV Vent hose hoping this might be the problem.

None of these things worked. Still have the issue.

I've been doing a bit of research on how the PCV system works, and there is a check valve integrated into the valve cover, that in vaccum is open and in boost is closed. I think it's plausible that this valve is clogged and not working effectively causing crankcase pressure to vary during vacuum and the car is compensating with STFT's. Or maybe not i dunno.

So, next I'm thinking of replacing the valve cover.

I'll have a bloody new car soon!!

Jebus mate, someone on the forum must be able to work this out. There is only a finite number of things it can be!!! I wish I was a diagnosis wizard and could tell you exactly what was going on here.....

[harms]

Mate even Jin @ Active isn't too sure...