legacycentral bbs

hi all,
i am based in the uk wales to be exact and took posession of a '93 legacy turbo today its been fitted with some saab turbo but if you stick your foot down basically anything above quarter throttle it just holds back and starts kangarooing down the road if you back off it pulls fine tho.
please someone help.
regards to all and good site
carl

don't know if it means anything but i replaced the ecu and it improved things a little also turned the boost down which also helped a bit

What about replacing the turbo with a stock unit?

What exactly is "kangarooing down the road?"

hi apparently the turbo should work fine on the vehicle according to garages in the area and it has only done 4000km so i would like to keep if possible.
as for kangarooing down the road the best way i can explain it is when you put your foot down and the turbo just comes up to boost then the car stops like you have pressed the brakes hard then it goes again then it stops again and it will do this untill you back off the throttle.however just been out for a drive and if you hold it on quarter throttle then it will go fine.
i need to get this fixed as it means the car can't be driven as it should be.

Sounds like Fuel Cut.

A fuel cut defender should solve your problems. I'm sure VRG3 will see this thread and reply with any info you'll need. He's the go-to-guy about this sort of thing.

Yes, I agree that it does indeed sound like fuel cut.

You could try fitting a fuel cut defender to see if it solves the problem. My FCD design is on this page:

http://www.graphics.cornell.edu/~v/fcd/

However, it's meant for North American models. I do believe your car has a higher factory fuel cut but does use the same sensor. What that means is that this FCD should work for your car, but it will affect the pressure signal earlier than necessary. That might work fine though.

hi thanks for your help are fcd dangerous as the fuel cut must be happening for a reason am i going to destroy anything by overiding it.i am probably wrong but i want to double check

The purpose of the factory fuel cut is to prevent your engine from overboosting, so it is indeed a safety feature.

How is your boost control configured? Maybe it would be better to first bring boost down below the fuel cut level.

Also, does the Check Engine light turn on?

hi
i could try turning the boost down again but its only boosting to half a bar now.just a few things i have tried changed the ecu and it made a slight difference but not a lot.somebody mentioned a test plug any ideas on this.
thanks

If it's only boosting to half a bar then you probably aren't hitting overboost fuel cut (unless your gauge is faulty and you actually are boost much higher).

The test connectors are the green pair of connectors under the dash. I'm not sure what test mode would do for you though.

Has the Check Engine light come on?

the engine light doesn't come on but it is working cos it comes on if you turn the ignition on.the reason it's only boosting to half a bar is cos its undrivable with the boost any higher.

how accurate is your boost guage? i believe the uk models had fuel cut set to 14.7psi

It's undriveable with boost set higher?

Does that mean that if you set boost low enough you don't get this problem?

Could this just be misfire? Have you checked your ignition leads and spark plugs?

This "kangarooing" is probably related to it being a saab turbo. I've driven a Saab 9000 turbo (high pressure version), which does the exact thing described, same reaction with the pedal. Floor it and you soon have it jumping off boost, slowing way down. Gradual throttle increase and staying off the floor will allow it to keep boosting. I think Saab puts this feature in to prevent damage to the turbo from excessive heat or pressure. This was in a non-intercooled car, so maybe that has something to do with it.

No, that would be engine management related, not turbo related.

Turbo's are simple in their design. The ECU is what controls everything that happens with a turbo. The action of a turbo is an effect of what the ECU tells the engine to do.

Weeellll... it's the wastegate that actually controls the turbo. And it's plausible that a wastegate could make boost fluctuate this badly.

But I've driven a bunch of Saab turbos, including a couple of 9000s, and haven't experienced anything like this.

Carl, I really think you should do a tuneup first. High boost is when it's hardest to ignite the air/fuel charge.

When my coolant filler tank leaked coolant into one of the spark plug holes, my first symptom (even before you could see any coolant underhood) was misfire on high boost. It felt just like a fuel cut.

i am going to change the fuel filter later this week and also plugs.i have tried rotating the coils and this made no difference is it worth changing them all.also benn offered a standard subaru turbo is this worth trying.

Ohhh... right, you don't have ignition leads. I forgot.

The early Subaru coil-on-plug coils do have a reputation for going bad as they get old. People sometimes replace them with four coils meant for distributor-equipped cars. I would first check the plugs before worrying about the coils though.

Well wether it's engine management or acutally the wastegate, i've driven a saab 9000 (auto) in good shape that had this condition and a legacy turbo (5sp) that did not. They were both stock, but the legacy had many problems (about $5K worth) and the 9000 had none. The 9000 has the kangarooing built into it.

ok just tried something and this may mean something to you i connected the test plugs and turned the ignition on for a bit then disconnected them and took the car for a run floored the throttle in 2nd gear and wahey straight up to 1 bar boost with no messing ran like a dream then within ten mins back to how it was.any ideas or was it just a fluke.

If you just connected the green connectors and then disconnected them, I don't think that would affect anything about how the ECU operates... I would say it's likely a fluke.

hi all begining to think its not fuel cut as i was driving today put my foot down and it seemed to misfire.so now thinking the fuel cut may just be a misfire but feeling far more severe as its hitting boost.could it even due to the misfire be building up pressure causing fuel cut.
the plugs in the vehicle are new but the coils aren't i have tried swapping the coils around but then that wouldn't make much difference so going to change them anybody know where i can order them online bear in mind they would have to be delivered to the uk.(it's quite difficult to buy parts for them here)
got to get this sorted before i put the car on lpg.

You may want to ask on the RS Liberty Forums about this:

http://www.rslibertyclub.org/

My impression is that it's actually cheaper to switch to standard coils with wires than to replace the OEM coils.

ok took the car out today and noticed it runs fine when cold the problem only occurs when hot.i am hoping this will mean something to someone as i need to get it sorted.

how big is the saab turbo? where is your boost guage plumbed into? I bet your just having overboost fuel cut. what revs does it begin to break down? could also be plugs........