Check Engine Light

[andyh]

Having a slight prob with my 9000 (1990, 2.0 Turbo 16, Manual). Last night the check engine light came on after about 30 minutes of driving and stayed on even after I stopped and restarted the engine. While the light is on the car appears to revert to base boost . Anyway, when I started this morning, the light had gone , but again after 30 or so mins driving was there again (with reduced boost). Its the first time I have seen this in 6 months of ownership. I have searched past posts, and found some stuff our about trionic cars and flash codes, but my car is non-trionic. Any ideas on what I should try first? May just end up taking to a specialist!

Also, i assume its okay to drive as I have to get to the airport early tomorrow!!

These may be unrelated symptoms, but I have recently noticed an occasional misfire at low revs, and a slightly soft-jerkiness to the acceleration at low revs.

Thanks in advance for your suggestsions! Andy.

[1989agoodvintage]

Well the non-trionic cars have a "brain" of sorts, a combination of APC and Jetronic. Take it to a Saab specialist with Tech2 and they'll be able to pull some fault codes out of it all being well.

[andyh]

Thanks for the reply Jason, I may end up doing just that. Just been out in the car again and the light is still on.

BTW I also noticed that if I turn just the ignition on, the warning lights go out in sequence, but then the engine warning light flashes 4 times, with a pause and then 4 times again and so on. In a trionic car this would apparently suggest the coolant temp sensor. Do you think this code means the same thing on a car of my vintage?

Also do you think the car is okay to drive...still goes okay, just boosts like an LPT. I assume that the ECU switches into "get you home mode" when the check engine light is on??

And.

[andyh]

Just done some further detective work on my problem. Please tell me if i'm barking up the wrong tree here.....

You may remember that a few months ago I posted a problem which was basically the car taking off on initial prod of the accelerator, but then power tailing off fairly rapidly. Well, I have since learned that for the APC/DI cars four flashes of the Engine warning light means knock sensor fault.

I suppose the two could be connected? ie: the performance problem is due to the ignition timing being retarded, or the car returning to base boost as a result of the faulty knock sensor. It certainally makes sense, and that is just what it feels like. Am I talking a load of old cobblers?? It does not explain for instance why the light has only just begun to appear??!

Assuming it is the knock sensor, is it going to damage my wallet to get someone to do it for me??

And.

[mark e]

Yes, Andy, it's quite likely that the two are connected.

Getting at the knock sensor is a bit fiddly- it sits under the inlet manifold. I haven't tried changing one myself, so couldn't comment on the spanner/swear rating. As for the cost of the part, again I don't know but I wouldn't expect it to be too expensive- it's only a piezo transducer.

[StephenA]

My old H reg 2.3 non turbo used to suffer from a knock sensor fault - it used to appear when driving down hill if I let the engine slow the car down rather than me using the brakes.

Of course being a non turbo I didn't get a major performance drop so it wasn't as much of a pain. For a while I got round it by disconnecting the battery for a bit which reset everything.

I eventually took it into the local dealer who did the job in less than an hour and the sensor was not too expensive (I can't remember how much it was but it wasn't a moment)

Steve

[JFP]

I had a check engine warning light come on, disconnecting the battery for half an hour seemed to fix it and its worked fine for the last 8 months

[andyh]

Thanks for the responses guys, I have tried disconnecting the battery, but the fault reappears fairly soon afterwards. I'm having the clutch changed at Saabtec in the next couple of weeks, so hopefully they can trace n' replace as necessary.

I'll let you know if cures the performance problems also. Will be a very happy bunny if so .