Wombat dumb Q4 question number 1 - Too much boost

Still getting used to this new fangled turbo idea, so a question I would be grateful for any help on.

I changed the thermostat today. Did the following to get to it:
- Took off the induction pipes from intercooler to manifold
- Took out battery
- Took off thebreather to separator hose
- Disconnected the idle actuator, took it off the engine and moved it to one side
- Removed a small bore pipe from a little solenoid valve attached to the slam panel

Put it all back together (did front brakes as a little side line as well), and now I have huge overboost.

I have read a few other threads on the pierburg valve (the last thing I mention above?), and seems like this might cause it.

The symptoms are quite well described in other threads, but basically if you boot the car, boost goes way way up (I have a boost gauge), and the fuel cut kicks in. Driving light footed its fine, and the car was fine last time I drove it a few days ago, so definitely disturbed something I think.

Any ideas appreciated.

Did you disconnect the electrical connectors to the pierburg valve at all? Sounds like the connections may have come loose or you reconnected them up the wrong way round.

Definitely a pierburg valve problem though.

Out of interest how much boost did you see on the gauge? Anything over 1.35bar is in dodgy territory.

Thanks Steve

Boost gauge is in PSI, and annoyingly, its also just out of line of sight behind the steering wheel, but I reckon it did not get up to 20PSI, but perhaps over 15, so just below that dodgey territory.

Got it sorted though. Used the tech manual resources here to read up on the plumbing, and then went back and had another look. Peirburg to wastegate pipe not connected. Actually a loose push on fit, so temp secured it and went for a run round the block. Cured.

And actually, with the car running at proper temperature, it feels much smoother and more consistent (or maybe the little run with no wastegate blew out a few cobwebs!!)

Quote:

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Originally Posted by Steve Webb

Did you disconnect the electrical connectors to the pierburg valve at all? Sounds like the connections may have come loose or you reconnected them up the wrong way round.

Definitely a pierburg valve problem though.

Out of interest how much boost did you see on the gauge? Anything over 1.35bar is in dodgy territory.

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ups, mine has 1,5 before went to remap quite long time ago,
and on WOT got fuel cuts even without high boost readings.
The first thought was also pieburg, but pieburg was OK.
In the service where i'm doing remap diagnosis was (beside crappy original map on modified engine) that fuel pump is almost dead, after exchanging to high pressure walbo gs342 looks like it's sorted. But many problems occured after that (mostly with fuel pipes on high pressure, but i'm sorting this right now, and still waiting on proper remap on dyno..)

but as Steve wrote, pieburg should be checked as first suspicious.


regards

WS

Glad you got it sorted, just a question though, where did you find a replacement thermostat? Original Q4 ones are like rocking horse shit these days.

Check the spark plugs too. When you reving up with midle throttle have you problems too? The reasons of doing that are
1. Pierburg valve
2. Air temperature sensor maybe water sensor too
3. Map sensor
4. Spark plugs (happens to me when the boost was over 1 bar)

Thermostat was from the following source:

info@alfa-service.com
www.alfa-service.com

Alfa-Service Hurtienne GmbH
Siemensstr. 32
D-59199 Boenen
Germany

About 86 quid including postage. I noted that Fiat Coupe 16v turbos are much cheaper and a bit more available but looks like you need to drill and tap the hole for one of the sensors. Didn't fancy that until I had seen one in the flesh!!