Caldina GTT not boosting properly

[Technohedge]

The ol caldina seems to have lost a bit of mojo. Its getting to normal boost pressure, but its not pulling anywhere as much as it used to. Not sure of its taking longer to spool up.

Compression test is fine, wastegate seems to be intact from when i had the downpipe off, seating/sealing well.

The turbine seems to be in good condition, hardly any radial or axial play in the shaft, no smashed up fins and spins freely.

Manifold isnt leaking, i fixed it a while back with some sort of clamp which seems to be holding just fine (i did find the old broken manifold stud when the downpipe came off though lol

only other thing to remark on is I had an aftermarket BOV fitted to it a short while back. The noise was doing my head in so i put the stock one back on and now under high boost i can hear the stock bov discharge? Im sure before it was silent? No hoses appear to be missing

Anyone have and ideas what else i can check?

cheers

[GDII]

How have you installed the stock BOV? They don't tend to work like aftermarket ones. At idle they suck in air through the outlet rather than seal like aftermarket ones. Not that this is your problem.
Maybe the diaphragm is torn.

[Technohedge]

The BOV does appear to be sealing properly. Ive just put it back in the stock configuration where it vents into the airbox. When I take it off and rev the engine it shuts and seems to not let any air through from what I can feel.

[Technohedge]

The Tvsv does appear to be doing its job as well. even if I disconnect the hose to it (running 'infinite' boost) it dosent accllerate with the same kick as it used to.

maybe a leak somewhere?

[whynot]

Something to check could be the knock sensor then. Didn't the 3sgte have issues with the knock sensor pulling power?

[Technohedge]

Possibly, is there any info on how to 'check' these?

cheers

[Mr Revhead]

A faulty knock sensor should show a CEL, code 52 iirc.

Have a look at this thread if you suspect the BOV
viewtopic.php?t=32156&postdays=0&postorder=asc&start=20

[Technohedge]

I'm not getting a CEL, am I to assume if there is no engine light on there are no codes stored or do I have to go looking for them?

Something else maybe to note, my rocker cover gaskets need doing, last time I had the plugs out two cyls had the plug holes full of oil which was covering the plugs somewhat. Could this be interfering with ignition? Would have thought it would be missing if so.

cheers

[Mr Revhead]

and now under high boost i can hear the stock bov discharge? Im sure before it was silent? No hoses appear to be missing



cheers

I'd be starting here... Do you mean when you lift off? or under power you can hear it? Been a very long time since I've been in a GTT so I can't say if you should hear it normally or not.

What has tipped you that something is wrong? Is it measurably down on power and gutless? Have you ever done a fuel filter?

[Technohedge]

Yea it seems to not be pulling like it used to. Not completely sluggish but definitely less than it was.

Fuel filter changed recently, nothing different after that

[whynot]

Do you have a boost gauge fitted? Is it running the same boost as before, I have plugged the turbo inlet on my car and pressurized the piping with an air compressor to check for leaks before. You might need connect the bov signal to the compressed air as well or it will bleed off but it works well as with the motor off you can hear any little leaks.

[Technohedge]

Yea it seems to boost the same as it did before on the gauge. Cant hear anything hissing if I rev it up from idle under the bonnet.

Thought about using compressed air to check for leaks, what did you plug the inlet with?

[whynot]

I think I plugged the inlet with a crc or spray can. Another thought, could it be a restriction in the exhaust. I have no idea what mods you have but a blocked cat or collapsed muffler would give the same boost and a loss of power.

[Technohedge]

has the downpipe off cat is fine, so I doubt its exhaust issues but another thing to check maybe.

Will try pressurise when I can sort it.

Bov is not the issue, I removed it and plugged the hole and still no difference.

Is there a good way to test the knock sensor while the vehicle is running? Don't want to go there unless I have to as its a pain in the ass to remove

cheers

[whynot]

I think there is a way to test it using diagnostics but I have not had to do it so can't assist with that. the usual test would be to swap it with a known good one.

[Technohedge]

Ok so it appears the Knock sensor is working, isn't grounded out and appears to show an ac voltage when I knock on the block with a bar

Going to pressurise the system when I get a chance and see if I can detect a leak.

Had a look at the compressor wheel earlier, seems to have a fair bit of radial play in it, however it doesn't seem to wobble at all when its running.

[Technohedge]

Ok managed to get some air in to pressurize the system, couldn't hear any leaking apart from around the intake pipe that surrounds the compressor inlet (I was using this pipe to pressurize)

Makes sense as I'm still seeing normal boost pressure on the gauge

So I'm left with fuel or ignition problems??? Changed fuel filter a while back with no change, I imagine if it was fuel starved then it would be pinging?

Could the injectors be screwed up in some way?

Going to check the plugs, however they were recently changed to new iridiums, again this made no difference to the performance.

[whynot]

Sounds like you are starting to run out of easy fixes. Have you checked the spark plugs to see if they look like like the engine is running lean or rich?

Have you checked the ignition timing recently, also have you checked the cam belt and cam timing. If it's skipped a tooth or if the timing has changed for some reason then you could easily loose power.

Has the sound or tone of the engine changed at all? It's hard to describe but sometimes you can pick a change in engine note or tone and I'm at the end of what we can diagnose without seeing it in person.

[Technohedge]

I pulled the plugs today whilst I was changing the rocker cover gasket, they had a fair amount of carbon on them, looks like a rich condition but I'm still not convinced it wasn't from the oil leaking past the threads as the plug wells were full of the stuff pre gasket refresh. Gave em a clean up anyway. Car sometimes smells like its pushing a bit of unburnt fuel out the back, however its not seeming to use more fuel than usual.

Timing is my next thing to check, is there any way I can do this when its running on the road or would it have to be with a timing light whilst on the driveway?

[GDII]

A timing light on the driveway would work once you put the car into test mode to check for electronic base timing but if the belt has slipped a tooth you will need to remove the top cam belt cover and line the cam gears up with the marks to check mechanical timing.