Just come back from another trip to the UK in my 2004MY Aero auto estate. I noticed on the motorway that, when flooring the throttle fairly quickly, the car misfired and wouldn't pick up for a few seconds unless I released it slightly. Seems to be when it's under load, and only at speed, around 80+mph (well, it was on a German autobahn ;D). I always use the high octane fuel. It's never done it before under the same circumstances, although to be fair it was June when I last travelled across Germany hence reached the relevant speeds.
I have two theories. Firstly, when I put the new plugs in a couple of months back I set them to 1.1mm, whereas I usually use 1.0mm. Secondly, I have never cleaned the throttle body in the 4 and a half years I've owned the car (in fact, never had to clean it on the last 9-5 either). I can easily adjust the plugs, but won't find out if I've fixed it for months, so I'd rather tackle the most likely cause first. Has anyone else had a similar problem? Starting etc. is no problem.
And never having cleaned a throttle body before, any tips?
Could be a partially blocked fuel filter.
Had a similar thing on a Ford a few years back, fine all the time and started easily but at higher speeds it would feel breathless and misfire.
The throttle body is best cleaned once removed, I used carb cleaner and brake cleaner with an old toothbrush.
Steve
I guess I might give it a whirl. Any idea how long it's likely to take to remove & replace on the 9-5?
Not long, probably take as long to jack the car up as to replace. A jubilee clip and 2 banjo bolts.
If your quick you wont loose much fuel.
Steve
I'd suspect the first signs of a failing ignition cassette.
Symptoms are identical....
Russ
Quote from: RussJ on 15 November 2011, 02:20:48 PM
I'd suspect the first signs of a failing ignition cassette.
Symptoms are identical....
Yes, though strange it didn't throw a CEL. It's normally very quick to pick up misfires on the DI.
Quote from: Steve440 on 15 November 2011, 01:18:52 PM
A jubilee clip and 2 banjo bolts.
MY04 might be bayonet release fittings on the fuel filter. Not sure.
You have yo remove the plastic cover first. Allow time for penetrating oil to soak in to the screw otherwise it's likely to snap.
Sounds like the failng DI fault I had on my old 9-5
Quote from: TomPaine on 15 November 2011, 02:28:02 PM
Quote from: RussJ on 15 November 2011, 02:20:48 PM
I'd suspect the first signs of a failing ignition cassette.
Symptoms are identical....
Yes, though strange it didn't throw a CEL. It's normally very quick to pick up misfires on the DI.
Not really, the early stages of DI failure will not give a CEL. You'll just count a few more misfires with Tech-II and possibly the extended DI test may catch it but otherwise it's not uncommon for them to give problems months before you'll get the CEL.
Quote from: Audax on 15 November 2011, 10:24:57 PMNot really, the early stages of DI failure will not give a CEL. You'll just count a few more misfires with Tech-II and possibly the extended DI test may catch it but otherwise it's not uncommon for them to give problems months before you'll get the CEL.
Well, in both my cases, previous 9-5 and current, the CEL was tripped at the first hint of a misfire. I'd never have known there was a problem had not CEL said there was.
Quote from: Steve440 on 15 November 2011, 01:18:52 PM
Not long, probably take as long to jack the car up as to replace. A jubilee clip and 2 banjo bolts.
If your quick you wont loose much fuel.
Steve
I actually meant the throttle body when I asked about how long to remove & replace :)! I've done fuel filters, but never fiddled with throttle bodies.
Well, I've just removed the plugs to regap them, and to my horror found they looked like this:
Cylinder 1
(http://farm8.staticflickr.com/7158/6404576389_889189bcb7.jpg)
Cylinder 2
(http://farm8.staticflickr.com/7012/6404576611_1ba180f1a1.jpg)
Cylinder 3 view 1
(http://farm8.staticflickr.com/7027/6404576793_030e3a6cd7.jpg)
Cylinder 3 view 2 rotated 90°
(http://farm8.staticflickr.com/7160/6404576981_7757ef7675.jpg)
When I last replaced them a couple of months ago they were fine :( . This probably explains the burnt oil smell that I noticed a few days ago. I'm now concerned as to what's causing it. I can only think of turbo oil seals, or valve guides. All cylinders seem to be affected, and if you look at the two views of cylinder 3 taken 90° apart, you'll see that there seems to be a definite difference between the two sides, perhaps where the petrol/air (and oil it seems now) mixture enters the cylinder, although the same effect doesn't happen on the outside cylinders. Oil consumption isn't particularly noticeable, although I did put half a litre in today I can't recall where it was on the dipstick after I topped it up before (it was still well above the minimum today). Any thoughts?
Is it definitely oil and not soot?
If its turbo seals you should see smoke on starting. And a lot of oil in the inlet pipes (there is always a thin film from normal breathing)
If its soot from running rich, you should see higher fuel consumption. Maybe a lambda sensor is failing.
Mmmm, lambda sensor. Yes, come to think of it they were sooty rather than oily, and a few times recently the fuel consumption hasn't been waht it was. Hadn't appreciated that a failing lambda sensor could cause that sort of thing. Bit difficult to tell with the smoke on startup, it's been pretty cold here and there is always a visible exhaust trail.
Is there any way of testing a lambda sensor? There's no CEL being thrown. I guess at 8 years old it's not excatly in it's prime!
I'm not 100% sure, but I think that the lambdas only look for a difference between themselves to check if the cat is working.
The first sensor out from the turbo is the one that checks the mixture. But they don't do anything on starting up. That's done on preset maps. Lambdas only come into play once the engine is up to temperature. At least ats what I was told.
I don't think that you can check them. We had one cleaned on the 9-3 but that threw a CEL. Maybe only because the second sensor after the cat was clean.
This might sort out the plugs, but I don't think it will fix the misfire. I'm sure the lambdas don't react that quickly.
I'm not even sure you are running rich. If its cold and you are doing short journeys, the engine will be running rich. It will be just like having the choke out. You really need to check the plugs after a run.
You can partially check that a lambda sensor is working with Tech-II, you watch the pattern it generates to see if it is reacting quickly enough and within the correct limits. Of course they can still show that they are OK when they are on the way out.
Quote from: sgould on 26 November 2011, 01:23:19 PM
I'm not even sure you are running rich. If its cold and you are doing short journeys, the engine will be running rich. It will be just like having the choke out. You really need to check the plugs after a run.
They've never looked like this before, and we haven't changed our driving habits in the last couple of years. It sounds like it's worth a punt to change the lambda sensor. I'm wondering now if the misfire was caused by it running too rich (or too weak) under the circumstances prevailing at the time.
I've just been investigating a local source of sensors, they seem to list two probes, a "regulating probe", Saab part number 4570909, and a "diagnostic probe", part number 4570917. Does one of them fit before the cat and the other one after?? And are these the right parts for my car (2004MY B235R)?
I think these are the right ones.
From EPC:
Article : Heated oxygen sensor
PartNo : 4570909
Usage : 2000-2010, B235
Unleaded petrol.
Front.
Order Quantity : 1
Article : Rear heated oxygen sensor
PartNo : 4570917
Usage : 2000-2010, B235
Unleaded petrol.
Rear.
Order Quantity : 1
Looks good then, the downside is that they are selling at €240 for the pair.....will have to think about this!
I've not looked at them closely. But they may have a Bosch part number on them. But non-standard pattern/generic parts may cause problems.
I had a pair on my old car after the Tesco fuel contamination saga. Consumption was 10% better. So a long time to recover the cost on fuel saving alone.
These were Bosch parts, so they should be OK.
But presumably, if it's running rich, it will damage the cat with a consequent need to replace?
The cat can stand a considerable amount of abuse long before it gives problems.
I would guess that the DI is failing. Not a bad idea to carry a spare and if the plug is pulled on Saab, they could become more expensive and difficult to obtain. As for the sensors, take a look at: http://www.aa1car.com/library/o2sensor.htm
Hi,
You can test the lambda sensor with tech 2 or some other readers. The specific limits are in WIS under "closed loop".
steve
I had a session set up with some diagnostic kit but it fell through, but I'm planning to kickstart it and will report back.