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My aero (96MY) has recently only been boosting in to the mid yellow where as until a few weeks ago it would go just into the red with no overboost. It still feels pretty quick though. The only things to have happened to it in the interim are a new clutch and slave. Oh the cat is rattly but I amtold its ok

Can anyone help and should I do an adaptation run (never done one before)

Thanks

Julian
 

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Hi,

It sounds like you've dropped to base boost (ie you're not getting the benefit of the turbo). You should check your hoses to make sure that there are no splits or loose connections also, if you have the equipment to get under your car (axle stands etc), you can check the Wastegate Actuator Rod which has a habit of coming loose. I found some pics on Billjs 9000 site (link above in the Saabs.net drop down list) very helpful when doing this. It's quite an easy fix (I've managed it and I know nothing about cars). Note that there should also be a clip to hold the rod in place once it's attached. This will probably have disappeared so the rod will be hold in place by tension alone until a more permanent fix is in place. If it does turn out to be the Wastegate Rod then send me a PM as I have some washers that will hold the rod in place.

Bills site also has instructions for the adaption run.
 

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That rattle from the cat is something that made me sit up and pay attention...

My '97 Aero dropped to base boost a while ago, but like you, i still had reasonable performance (specifically at high revs) and a rattle from the cat.

It turned out to be the inner flap dropping off the wategate arm - so from outside, everthing appeared fine (because it WAS fine!) - but inside the waste gate casting, the control arm was waggling away, unable to close the exit hole and stop all the boost running away down the exhaust.

this expained the availability of some boost at high revs (the arm, minus flap, was still able to RESTRICT flow out of the exhaust, just not stop it completely when the gases got really flowing), and also explained the rattle from the cat, which was where the bits of wastegate that had broken off now resided!

If your actuator rod is still attached to your wastegate control arm, and if you can take the black plastic piping off the inlet side of the turbo (a jubilee clip), start the engine and see the turbo spin, I'd say that's what's happened to you too.

When I removed the downpipe / cat and tipped it upside down, out came the bits and pices of wategate! (I didn't do this when I fixed the turbo, I did it later when I fitted an abbott de-cat / downpipe, and in the mean-time, I had the rattle diagnosed as starter-motor bearing failure by 2 different garages - I'm glad I didn't believe them)

Solution? Buy a blown secondhand turbo and use the wastegate casting to replace your own (the td04 is only held onto the wastegate with a single-bolt, glorified jubilee clip) - it cost me £40 and I fixed it all myself in the driveway in about 5 hours total.

Carl
 

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The boost on my aero was only making it into the mid yellow a few months back. Turned out to be a split in the pipe to the boost gauge just before it goes through the bulkhead. I replaced all the small bore rubber tubing in the end and found several very small holes elsewhere.

On the other hand, if the boost is only making it into the bottom of the yellow then it may be that your waste gate rod has come off (something that happended to me a couple of weeks ago).
Kev
 

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After all the vac hoses could check the APC solenoid - should be 3ohms acros the centre to each outside pin.
I lost all boost on my GM900 recently and after trying everything know it turned out to be silencer box restricting exhaust flow which just wouldn't allow turbo to spin up.Might also be worth checking your plugs.


Mike
 

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I had the same problem on my Aero recently. It was a failed APC solenoid valve as LocoSaab has suggested. However, mine was fine electrically, but had failed internally; the small metal disc inside had broken into 3 pieces and sealed the R port, leaving the C (compressor?) port permanently connected to the W (wastegate) port. This results in base boost only. To check if all is OK including wastegate actuator, wastegate itself and if all is mechanicvally connected do as follows:

1. Disconnect all 3 hoses from APC Solenoid
2. Block up the C hose
3. Connect R to W with a bit of pipe
4. Cable tie hoses so the fan doesn't eat them
5. Go for a VERY CAREFUL test drive
With this setup there is no negative feedback to the wastegate so it will not open. As you give it a bit of throttle the turbo will wind up with nothing to limit it and you will hit overboost very easily. When I did this I managed to spin the wheels at 45 in 2nd without trying.

If this doen't get the boost back there must be something else amiss.

Paul
 
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