SAAB 93 Judder!

[rallykarl]

Hi, I wonder if anyone can help. I have a 93 1.9tid on an 05 plate. I have noticed that occasionally there is a definate judder when gently accelerating. It doesn't happen all the time, but its noticeable. It feels like the car is wanting fuel. Almost like its missing. Has anyone got any ideas? Cheers Karl

 

[pgarner]

Mass air flow sensor would be a first guess.
when was it last serviced?

was going to say turbo vanes sticking but doubt the 93 will be VNT turbo.

has the turbo ever been checked over - just thinking it is 17 year old if not.

im starting with worst case, well excluding the maf, hopefully someone might have a better ideas for you to check

 

[rallykarl]

Thanks for that. I dont know what a VNT Turbo is. My 93 is 2006. It was service about 3 moths ago, but I've only recently bought the car.

Is there any way of checking if its the Mass Flow Sensor?

Thanks again.

Karl

 

[pgarner]

sorry still half asleep when i typed that tought the car was frm 1993 not a 93. so it is more than possible that it could have a VNT being 2005

the VNT turbo allows the airflow over the turbine to be changed which allows very little lag to full boost. the actuator can stick especially if its doing alot of motorway miles where its hardly moving. WD40 is great for freeing them up.

MAF can be checked by disconnecting it and seeing if it runs better, however as it is an intermittent fault it may feel worse more down on power all the time.
the only other way would be to try and find info on what the maf whould be flowing (flywheel power * 1.25) against what it is. this does require diagnostic software and some who actually nows how to use it.
too often than not the maf may be on its way out but as there no fault logged then most garages will tell you its fine.

cleaning it may help temporarily. take the MAF out and clean with electronic cleaner or carb cleaner and allow to dry and refit. dont sit it down until its dry to prevent contamination

 

[rallykarl]

Thanks again for this. Is it easy to remove the MAF to clean it? Also, if after cleaning it, it helps temporarily, would the engine need to go through the diagnostic, or could i just bolt a new one on?

Not sure that it feels like a turbo problem, more sensor or fuel.

Cheers

Karl

 

[pgarner]

dont know some can be a pain to get out in the way that you need special tools (security bolts etc ) so you have to take it to a dealer. if you can get the screws out see a good hardware shop to see if they can give you similar screws with normal heads on them.
new one should just bolt on without any issues.

remember that the maf measures the airflow so if gets low readings then the engine will inject less fuel but the A/F ratio will be out - more air will be going over the maf than it thinks.

 

[rallykarl]

I thought I should add that the loss of power is instant. It just seems like the car is struggling to go, but only for a split second! Does that sound like anything?

 

[rallykarl]

It also only seems to happen when the car is warm and has done a few miles.

 

[pgarner]

maybe a coolant sensor.
you really need to find someone with diagnositcs and knows how to use them. check the likes of boost, maf, fuel trims while the cars actually running on the road.

might even be someting as simple as a split vac line

 

[T9 man]

Have a good look at the sensor loom lines immediately below the front plastic engine cover, as this is easily damaged, multi point connection between plugs and sockets made not quite secure by independents poking around underneath the bonnet unsure of where things are exactly.

Listen out for a soft ticking/hissing sound from the engine, which can be a manifold issue for the turbo i.e letting air in and out at the wrong place.

All though the car was serviced 3 months ago, who was it done by? was it a Kwikfit special or a Saab dealer or an independent Saab specialist?

What was the mileage that the level of service was based on? this is often an indication as to what has actually been replaced or checked on the car.

I am assumming that the engine diagnostic light has remained off so far?
Let me know how you get on,

 

[Aikmanson]

Um, if it happens when it is hot after a few miles, could be a coolant hose splitting. I would check all vacuum hoses and coolant hoses first, it is free to check yourself.

MAF sensor maybe, I do not know much about newer Saabs, T9 man is your best bet.

 

[rallykarl]

Thank you for your help with this. Its not getting any better, in fact it did it this morning on the way to work!

I will take it into SAAB and offer your words of advice to them and see if they can identify any of the points you have come up with.

I am greatful though. Its a real shame, as Ive always wanted a SAAB and I wanted it to at least run well.

I'll let you know how I get on.

Karl

 

[T9 man]

The Best of luck with it! and don't let this fault put you off Saab's? every car has their own set of special quirks/problems, but once repaired you will be rewarded with a very unique vehicle.

 

[rallykarl]

took it into saab. they said they checked everything, but couldn't find a problem! They said i should leave it for a while to "let the fault develop"

 

[snake23]

Hey, I'm a newbie to this forum lark but, I also have a 9-3 TiD 150, and had exactly the same problem and the same worries. I bought my car from a great SAAB dealer and after having my first taste of the judder I called them. Their tech said it was the DPF (Diesel Particulate Filter) getting blocked, when the pressure sensors notice a fall in pressure downstream of the DPF in the exhaust the ecu induces a missfire to heat the exaust and the DPF to burn away the soot (DPF regeneration). As you say it only happens when the car is warm and you're doing 60mph ish..... I've had my car from nearly new and it still runs great... Hope this helps..

 

[T9 man]

Hey, I'm a newbie to this forum lark but, I also have a 9-3 TiD 150, and had exactly the same problem and the same worries. I bought my car from a great SAAB dealer and after having my first taste of the judder I called them. Their tech said it was the DPF (Diesel Particulate Filter) getting blocked, when the pressure sensors notice a fall in pressure downstream of the DPF in the exhaust the ecu induces a missfire to heat the exaust and the DPF to burn away the soot (DPF regeneration). As you say it only happens when the car is warm and you're doing 60mph ish..... I've had my car from nearly new and it still runs great... Hope this helps..

Marvellous, glad you got the fault diagnosed! this tends to happen if the car is only used on short runs apparently and needs a good long run every other week to prevent the filter from getting clogged.