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9-5 vibration on idle

14K views 19 replies 9 participants last post by  xLordJeevesx 
#1 ·
Hey, guys. Been on this website too much since I have been slowly bringing my 2000 Saab 9-5 wagon back to good health.

I have been unfortunately having a lot of problems with my Saab recently. It is on its 137k mile mark and showing lots of signs of an old car. The main problem I am having with my saab is the engine vibration.

There is a nasty vibration when sitting at idle. It goes through the steering wheel and makes your teeth rattle. :x Though, once you get going and gain some rpms, the rattle is gone and it drives like any other car. Is this a motor mount issue? It seems that once I get going though, the rattle would intensify.

Any help would be appreciated. :)
 
#2 ·
Almost certainly the mounts, three of them and not cheap. If you want to check, the easiest one to get to is under the "U" shape engine bracket above the serp belt. Remove the bracket and then try to move the bolt in the centre of the mount. If should be very very stiff, mine could be moved with a little finger.
 
#3 ·
Sounds like you need new mounts. There's four of them: one behind the engine, one under the battery, one under the front, and one on top under the big U-shaped bracket. Like saabtwin says, start with the one under the big U-shaped bracket. It'll cost about $100. I recently changed that one out on my 9-5 wagon and boy did it make a big difference.
 
#5 ·
#11 ·
It is an auto. It happens just when the engine is idling. Regardless of gear.

I'm picking up just BCPR6ES-11's down the street from my gym. For a set of BCPR7ES-11's, I would have to drive about 30 minutes. ;oops:

I will look into checking for vacuum leaks.

I will update once the new plugs are in tomorrow. It would be awesome if those do the trick. :D
 
#13 ·
I'm picking up just BCPR6ES-11's down the street from my gym. For a set of BCPR7ES-11's, I would have to drive about 30 minutes. ;oops:
I was also going to suggest plugs as one possible maybe. You may want to be careful about changing the heat range of the plug, which is what you'll be doing with the alternative plug you say you'll be using.

If you don't know, the first numeral in the NGK plug identification code denotes the heat range of the plug, with a lower number being a 'hotter' plug and higher being 'colder'. If you use a '6' instead of a '7' then the plug will tend to run hotter and this will increase the chance of pre-ignition (from a glowing spark plug tip) under heavy load.

This isn't to say that you will get pre-ignition, but the chance at least increases, and my understanding is that supercharged engines tend to be more prone to pre-ignition problems than are naturally aspirated engines.

Please preface the following paragraphs with 'it's my understanding that";

If pre-ignition does occur, then I'm fairly sure this would be detected as a 'knock' and the ignition would retard, but since in this case the (pre)ignition event is occurring at the plug before the plug actually fires, retardation of the spark may not help.

I put "at the plug" in italics because spark retardation would tend to help reduce / eliminate knocking if the pre-ignition were spontaneously originating from another point in the combustion chamber and thus creating two flame fronts (one originating at the source of pre-ignition and the other from the correctly timed plug firing). In this case the two rapidly expanding flame fronts will collide and cause a possibly severe 'knock' against the rising piston. In this case retarding the spark will retard the point at which the two flame fronts collide, when the piston is higher in the cylinder, lessening the severity of or even eliminating the knock.

But, with a single flame front originating too early (possibly much too early) from an overheated plug (too 'hot' a plug), the flame front will prematurely collide with the rising piston, and cause knock, so in this case retarding the spark (which in this case isn't the source of the single ignition event, as it fires after the horse has bolted) will not retard the point at which the flame front collides with the piston crown, and knocking won't be reduced.

Uncontrolled knock is a bad thing, and not always kept in check by the knock sensor. Knock sensors can only really help with minor knocking events, such as you might get with the wrong grade of fuel (which tends to create pre-ignition originating from some point other than the spark plug, i.e. tends to create two flame fronts, so more amenable to spark retardation).

Some manufacturers recommend more than one heat range plug (for use in different conditions), but it doesn't seem that Saab lists the '6' plug as an alternative to the '7' (at least not in the handbook), so I'd be careful about using it. About the only time you might want to risk a hotter than standard plug would be in an engine that tends to foul the plugs, such as one that burns a fair bit of oil (the hotter plug tip will tend to stay cleaner because the heat helps burn off deposits, helping prevent misfiring).

Regards,
John.
 
#16 ·
Installed the new plugs. Engine definitely starts way better and gives me more confidence. You would get a very rough start sometimes. The spark plugs in there were some cheap autolite plugs. Pretty old and worn.

Unfortunately, still vibrates. But, I have figured out that if you put pressure on that U-bracket mount in a turn with some simple g-force, you can definitely hear and feel it.

New mount is coming in on Saturday.;ol;
 
#18 ·
Installed the new plugs. Engine definitely starts way better and gives me more confidence. You would get a very rough start sometimes. The spark plugs in there were some cheap autolite plugs. Pretty old and worn.
In that case, might the DIC be suspect, considering all I read about it being so prone to damage caused by wrong / worn plugs?

Unfortunately, still vibrates. But, I have figured out that if you put pressure on that U-bracket mount in a turn with some simple g-force, you can definitely hear and feel it.
Yet there is still some poor ("rough") starting? Has the idle problem completely disappeared? You had poor idle before, tends to suggest any "g-force" related symptom might be a separate issue since there won't be any g-force happening at start up or idle...??

Regards,
John.
 
#19 ·
Let us know how it goes with the new mount.


I can tell you I have run every plug known to man and data logged most of them in my old OG9-3 making 300HP and found a slim margin of difference in the plugs during normal operation.

The only real difference i saw was that non NGK's tended to wear out a little quicker.
 
#20 ·
Got the new mount on! Works great! :cheesy: Engine light is off now. Runs smooth as butter!

Even a person like me who has had very little time holding a ratchet had no trouble at all doing it. Simple prop up the engine with a jack and block of wood, take off that funky U-bracket, unbolt the old mount and then just reassemble.

Thanks guys for your help. I luckily got a new mount for free from a family friend. :)
 
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