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Discussion Starter #1 (Edited)
Hi, I've got problem with my Saab(B202, '90).
The engine is knocking. When I accelerate hard It starts at about 2500rpm and after 4000rpm it's ok again. When I don't accelerate (only drive at certain speed) it knocks all the time. When it's cold you can hardly hear it, but after 10km there is no way to miss it.
Hmm... I don't know how to describe the sound:confused:
It's the same sound as the engine knocks for about 2sec after it starts (maybe only my engine does it).

There's no problem with oil pressure.

Thanks for any ideas.
 

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Bear in mind that America uses a different octane rating, so their 94 is more like European 99. Anyway.

It's hard to diagnose sounds. Just to avoid any misconceptions, I'm assuming that the knock you are getting is the kind of noise the engine would make if you try to pull away in too high a gear. Metallic rattle. If this is not right then we'll have to guess again. But we need a bit more information.

How do you know it is not connected with gasoline/petrol? Does it knock when you use high octane? Knocking is basically going to be caused by running lean, ie underfuelling, so something in the equation is not working. Is this on a turbo car? If turbo, have you tweaked the APC? Manual or auto? Are you using the correct plugs and are they gapped right? What is your timing set at? Any vacuum leaks? When was the fuel filter last changed? How about plugs, rotor arm and dizzy cap? What do the plugs look like if you pull them? Maybe worth cleaning the FPR, and checking that the injectors are flowing properly.

Welcome to Saab Central (both of you) :cool:
 

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Could very well be something non engine that's loose. Check AC compressor mounting bolts and things like that. COuld be you just need to run some Methyl Hydrate through your tank because you have poor fuel.
 

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Discussion Starter #8
Jezzadee said:
How do you know it is not connected with gasoline/petrol? Does it knock when you use high octane?
Every time. High octane, low octane, LPG gas (I've got an LPG installation), no matter what I'm using.

Jezzadee said:
Is this on a turbo car?
It's manual 2.0 16V non turbo.

Jezzadee said:
Are you using the correct plugs and are they gapped right? What is your timing set at? Any vacuum leaks? When was the fuel filter last changed? How about plugs, rotor arm and dizzy cap?
Plugs are ok, almost new, gapped right. No vacuum leaks, I hope;). Fuel filter changed one month ago. I don't know anything about timing.


I don't think it's connected with fuel. It started to knock couple weeks ago, earlier everything was perfect.
I try to tell you sth more.
When I drive without accelerating it knocks and when I start to accelerate it stops, then after 2500-3000rpm knocks all the time. No matter I accelerate or not.
It's definitely something inside the engine. Metallic sound.
Maybe rod bearings or main bearings - but there's no problem with oil pressure.

Thanks:)
 

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Dull or pingy? Whats the interval like? Does it rise and fall with the RPMs?
 

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So it sounds like engine knock then?:cheesy:

Get someone to rev the car while you are over the engine just to be sure that it is not something erroneous. All of these suggestions have been good...its got to be something!
ALthough these cars have bullet proof bottom ends, you never know.
Clutch is all good?
 

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Discussion Starter #12
jetman said:
So it sounds like engine knock then?:cheesy:
It's definitly that ! Thanks !:cheesy:;)


jetman said:
ALthough these cars have bullet proof bottom ends, you never know.
What do you mean? And what about rod bearings as I've said. Could it be that?

Maybe tommorrow I'll try to record it, to give you a sample of my knocking:cheesy:.
I'll also check timing, but I think it wouldn't be connected with the engine temperature then (the higher temperature, the higher knocking).
 

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You mean con-rod bearings? I've never heard of it happening per se. How's your head gasket?
 

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Discussion Starter #14
Yes, con-rod bearings, not main bearings.
How's my head gasket? Hmm... Honestly speaking, I don't know:confused:.
 

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I had big end bearings go due to driving for a few hundred miles with coolant in the oil. Head gasket had gone but I didn't notice...
 

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It sounds just like the knock on my engine. Fine at low revs, but over 2500 it makes one hell of a rattle.

Check that your timing chain isn't flapping about loose. Failing that, it's most likely con rods / big ends. I know it's hardly heard of big ends going on 900's, but it was that on mine.

Just don't ask how much it cost. Put simply, it's not just a case of dropping the sump and doing it all engine in-car. There's a gearbox in the way, that needs to be separated from the block. On the bench.

Sorry to bring possible bad news, but.... it's for the best.

Of course, it could be something else. Tappets? Really loud tappets?
 

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I had a problem similiar to this. It turned out to be my crank pulley. It ened up having a hairline fracture in it so it was moving and it sounded just like rod knock or piston slap, the noise similar to a bad bearing. I found the problem when I fixed my oil leak, when the crank pully broke putting it back on. I put a new one on the the noise was gone. On closer inspection of the pulley I saw marks on the back of the pully where it was rubbing on the timing chain cover. It might be worth a look or if you have one layin around swap em out, see what happens. Hope it helps..
 

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Discussion Starter #19
I put the microphone near the engine and took a ride:)
Normally I don't drive like that (I mean high RPM's) but I wanted to give you a good sound:cheesy:.

It's here:
http://briefcase.yahoo.com/ login: saab_knocking; password: saab900

Thanks for all your replies, suggestions, etc...;)
 

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That's exactly the same sound as mine makes.

OK chaps of Saab Central...

What is it? Then perhaps we can both get it fixed.
 
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