Petrol Turbo diagnostics

[mjb]

OK Here's the story with my Dad's tubby: the turbo isn't working. 0-45mph in 18 seconds on the flat, can't hit 4500rpm in 2nd.

No MIL light

No collapsing of the intercooler flexi-hose when revved hard from idle, suggesting the turbo vanes are turning freely so I suspect something to do with the wastegate's gone south

The ECU reported the boost control solenoid's knackered, so I gave it a clean, cleared the fault and got the ECU to test it. It clicked when tested. The ECU reports it's activating the solenoid when revved hard and hasn't flagged another fault. The original fault could have been me previously disconnecting the valve with the ignition on.

How do I go about seeing if the wastegate's gunked up and stuck open? I've worked out I need the corner jacked up, and wheelarch liner (AAARRRGGGHHHH!) removed, but have no idea what to look at. Any other suggestions? Would a collapsed cat kill the turbo? Could a crud-filled fuel filter or dodgy fuel pump have this much effect?

[Doggy]

Can you determine if you've got normal boost pressure somehow? - if not, you can ignore the exhaust.

Forgive the bl00dy obvious, air filter?

[mjb]

Can you determine if you've got normal boost pressure somehow?

Between the turbo and the inlet manifold? Hmm I'll plug the PP2000 in this evening and see if I can get a MAP reading. Otherwise I ain't got a clue how to test it. Is the wastegate supposed to be open (bypass) or closed (exhaust drives the turbo) when the solenoid hose is disconnected? When I revved the engine with the solenoid disconnected there was slight suction from the manifold hose. If the wastegate is normally closed, then I'd expect a good few PSI blowing out of it...

Couple more points of note:

There's no noticeable change in pressure on the intercooler hose when you pinch it and rev the engine (dunno if it should noticeably push back at all when boosting - can someone with a working tubby have a check for me please?)

There's also no whistling when revved, either the sound of a turbo or a hose/intercooler leak

Forgive the bl00dy obvious, air filter?

I'm pretty sure I've checked that, but I'll re-check

I also haven't checked the coolant level (which I know kills the turbo when it's too low), nor have I checked the dash bulbs yet, but as I say the engine ECU's not got any faults showing

Where's niz when you need him?



OK I've looked at a few garrett turbos on ebay and it looks like what I think is the pneumatic actuator for the wastegate (3" round metal thing with a hose attached I can see through a gap in the wheelarch liner/subframe), should have a metal rod sticking out the back, presumably the other end of which is attached to the wastegate... If I get the car in the air, should I be able to move this rod back and forth with my hand? If so, how far should it move and how much force would I expect to need to move it?

[mjb]

Thinking about this... the wastegate should normally be closed (boosting) shouldn't it, as the actuator needs pressure to work, and the only way that pressure's going to get there is via boost pressure (and then the ECU switching the solenoid to allow the pressure into the actuator)

So if there's mild suction on the manifold air hose to the solenoid, there's never going to be any boost... which means either the turbo's seized or the wastegate's open, and given how mild the suction is compared to an ICV hose, I reckon it's got to be the wastegate not shutting, unless I'm being stupid...

[mjb]

Manifold pressure...
367mB (5psi) @ 800rpm
300mB (4.4psi) @ 1240rpm
293mB (4.3psi) above that
200-220mB (3.2psi) on over-run
up to 1000mB (14.5psi) when revving (which it does VERY responsively in neutral!)
BBC reckons the ambient air pressure is around 1000mB today

solenoid fault (short to positive) has also reappeared.

I don't know what to make of it



interesting side-note: fans enter full speed mode when the coolant temperature reaches 106c and stop when it's down to 102c (as reported by the ECU). Also wherever the IAT sensor is on this car, it's wrong unless it's 60c outside

[steve_earwig]

Not that I can be of any help at all here (never had a car with a turbo other than a smoker) but I had a squint while I was in Pervert's Socks and there's meant to be a temperature probe on the same gizmo the throttle pot's bolted to.

[mjb]

there's meant to be a temperature probe on the same gizmo the throttle pot's bolted to.

Ah of course! Above the TPS and opposite the heater iirc. Thanks

[teamster1975]

I'll be watching this with interest Matt; I've been intermittently losing the turbo on mine and there is no rhyme or reason.
Strangely it seems to have been a lot better since the weather has gone cooler

[mjb]

Can you see the low coolant dash light from where you sit? I used to get intermittent turbo issues I couldn't work it out until it happened on a 'fun' drive when I was sitting upright and I saw the evil orange icon...

[teamster1975]

Nope, not had that since I basically replaced the entire cooling system!
Also you remember I mentioned that I was getting the engine diag light on intermittently through the summer? Well I've not had that come up for about 3 months or so either; the two must be related.

[mjb]

You need the ecu read

[teamster1975]

Indeed!
I'll get the stella in my friend

[Doggy]

Guessing from the above that the turbo etc. is OK & you're thinking dodgy temp. sensor confusing the ECU....

Did you get to the bottom of it, Matt?

[mjb]

Guessing from the above that the turbo etc. is OK & you're thinking dodgy temp. sensor confusing the ECU....

Did you get to the bottom of it, Matt?

Nah, it's still slower than a 1 litre corsa

When I've got my coupe running I'll give the tubby a turn in the garage (too cold+wet+windy to work on it on my driveway. God I'm spoiled by my garage!). I REALLY hope I don't have to take the wheelarch liner off to diagnose/fix it. Single worst job on a 406 unless you've fitted new screws, washers and liners. (I'm 2/3 the way there on my coop! )

The temp sensor's just a side issue. When the engine's cold and at idle, there's a ~20% chance of it stalling as soon as you press the accelerator (otherwise it'll just /nearly/ stall). I'd normally blame that on the CTS, but seeing the ECU reporting the ambient temperature that high... As it is though, I actually have a tubby CTS in my toolbox I may as well chuck in the car. I just don't know how to replace it (the reason I didn't replace it on mine 3+ years ago) as it's hidden away at an angle you can't get a spanner to. I think I'll just plug the PP2000 in when it's cold and see what it thinks the temp is before getting off my arse

[Ar9yle]

MJB
hope this helps as Ive had an almost similar issue with my HDi, see my original post seemed like the turbo was not working, Put car into Peugeot dealer today & they diagnosed a throttle adjustment clip which prevented the throttle opening fully, 97p +VAT for the part, car now goes like an Exocet rocket. Downside was the £70 +VAT for the dyno test.

Thought it would be worth you checking this first although not sure where the part is located on the engine/bulkhead.

Regards