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Help Please -Misfire

1079 Views 8 Replies 5 Participants Last post by  earthworm
I have tried using the search feature but it does not seem to have helped me. So PLEASE can anybody offer any ideas

I have a 1997 900 which has been marvellous except for a missfire which has cropped up on occasion over the last 18 months and is now almost continuous.
My son mainly uses the car so please excuse me if I am a little vague on the symptoms. The local non specialist garage has looked at it a number of times but not been able to permanently cure it. We have now taken it to a garage which specialises in Saab, and they are unable to find what causes the missfire. I have found when I drive it, the miss is when you are on a constant throttle and that if I accelerate hard there is no problem, but when I go back to a steady throttle opening which probably giving me between 50 to 60 MPH the miss is back. The garage have investigated the electrics and not come up with anything but I would be grateful for any suggestions as it is becoming very expensive - its been in the garage for 3 days:cry:.

The mechanic who is looking at the car is suggesting checking the crank case sensor but to do this will break it when it is taken out. Anybody know what this sensor does and can it cause a miss fire?

Could it be fueling? A while ago, my son put in a tank of BP's High Performance Petrol, (Optimax?) in the hope it would help the misfire, but found that the car was worse on it.

Any suggestions would be most gratefully received.

Simon M
1 - 4 of 9 Posts
She is a non turbo.
I am sure that they will have swaped the plugs they have been taking parts off a similar model ( distibutor cap, leads etc) and trying them to see if it makes any diference but no luck so far. I will check if they have done the plugs on Monday morning. I am told that she had the wrong cap etc but changing them has still not been the answer.


Simon M
Thanks for the ideas guys:cheesy:

When the garage ring me later this morning to give me a price for a new crank case sensor I will make the suggestions that you have raised. Hopefully one of these may solve the problem otherwise I supose the only route to go down is the crankcase sensor. Any one know if the signal from it can be tested with out replacing it? I am told that to take it out will break it but I wonder if a signal can be picked up from the lead?

Simon M
The problem has been solved at last:cheesy::cheesy:.

Whilst moving a vacume pipe the mechanic found that the engine ran normally.
The pipe was attached to the wireing harnes with a cable tie. The vacume pipe being O.K he opened up the wireing harnes and found that there was a problem with a wire going to the injectors, re made the joint or reconected the wire and now she is going well once again.

Thanks for you help guys.

Simon M
1 - 4 of 9 Posts
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