: Misfiring and no power
04-23-2003, 03:44 AM
I trust you all had a nice Easter break? I went to Edinburgh for a few days and in the 1000miles of driving I did the car behaved impeccably, and did so for the next few days after returning home.
But, yesterday morning it started misfiring (I think), running very roughly. This is present at all revs, from idle up to running speeds, and there is a consequent loss of power. The exhaust smells very strongly of petrol, although it is not smoky. I took off the DI unit and pulled all the plugs which were all uniformly black, so it doesn't appear to be a particular cylinder that is affected. The idle speed is normal and stable (at about 900-950rpm).
The check engine light doesn't come on or flash so the management system doesn't seem to think there is a problem. So, has anyone got any ideas? Is it most likely to be the DI cartridge? (which is 9 years and 136k miles old).
For what it's worth, over the past year the car has very occasionally stuttered slightly, always occuring while motorway cruising (or at least this is when I've only ever noticed it). It only lasts a second or two and then disappears. Could this have been an indication that the DI was on its way out?
Everything under the bonnet looks fine. As well as plugs/ignition the Haynes manual suggests other things such as the fuel pump, the fuel injection system in general, blocked crankcase breather pipes, and probably some other things I've forgotten.
Any help would be much appreciated!
p.s. does anyone on this list own a 9000 CS with the registration number M900OCS? Nice. I saw it in Edinburgh last week.
I am no expert (as most know http://www.saabscene.com/forum/images/smilies/rolleyes.gif ) but the surefire way to diagnose the DI is to replace it with a known good one.
MarkE was having problems with his 9000 2.3CSE a few weeks ago, so we stuck my DI on his Saab and it ran just fine.
So, yes, it may be the DI ...but someone more expert will be along in a moment to give you the correct answer.
04-23-2003, 04:43 AM
thanks for the suggestion. Now all I need is a kind-hearted DI-equipped Saab driver to be passing Wokingham with 30 minutes or so to spare one evening!
04-23-2003, 08:29 AM
Not had quite the problem you have listed.
However I have had misfire problems before.
Causes I have found are usually
1/. Dead Plugs cheap ones last 6k on a Turbo before going off and by 12K seriousely bad.
2/. Leads, and distributor cap if you have one.
3/. Ignition coil dieing
4/. Blocked injectors
I also have found that cleaning all the "in line" Air sensors and bits between the Air filter and the injectors helps economy no end.
I took them off and sprayed with break cleaner until they looked clean and stopped running black.
Do not recomend this unless spares are avalable for more expensive Air Mass sensor.
Thinking about it very very badly blocked injectors might cause some of the problems you are having?
I think the Di module though might be worth checking if the problem was "sudden" as opposed to gradual with all the problems I have listed above.
Sorry not near enough to Woking to help.
04-23-2003, 08:41 AM
Thanks Bill. The plugs were changed 1k miles ago and looked fine (apart from perhaps being too black - fuel/air mixture too rich?). My suspicion is the DI unit, which I've heard is prone to failing with age. Mine's 9 years old and has 136k miles worth of firing under its belt.
04-23-2003, 09:57 AM
I can only think of two causes for your symptoms. Either, the ignition is failing to ignite the sparks, in which case it's the DI, or the mixture is excessively rich for some reason.
On an LH system with an Air Mass Meter, if a leak develops on the pressure side of the inlet between the AMM and the manifold then a rich mixture situation will occur. This is because the AMM adjusts the mixture for the amount of air going through it but all of that air isn't going into the engine hence the incorrect fuel/air ratio with misfiring and poor performance. If there was a faulty sensor the "check engine" light would show.
The only time I experienced this was when the bottom intercooler hose was leaking at the clamp but I could hear this from inside the car.
I suspect that a Trionic system would show the "check engine" light with such an air leak, but I might be wrong and even if it didn't I think you would get different symptoms with a MAP instead of an AMM.
Either way it is worth checking for air/vacuum leaks before changing the DI
04-23-2003, 01:31 PM
Hi all, since I got home from work I've tried a few things, so time for an update.
First off I've checked for obvious leaks and can't find any.
But, I have been fiddling...
With the engine running I disconnected power to each fuel injector in turn. 3 times out of 4 (cylinders 1, 3 and 4) this made the car almost stall, but one time (cylinder 2) it made no difference to the rough running. So, I checked the spark plugs, and the one from that cylinder was much blacker than the others. Maybe a duff plug? If so it should behave the same way in a different cylinder. So, I swapped it with the plug in cyl 1 and did the same injector-disconnecting. When I disconnected the injector from cylinder 1 with the suspect plug the engine almost stalled, whereas when I disconnected the injector from cylinder 2 which originally made no difference, there was... no difference.
I hope this makes sense!
So, does this tell me anything useful? Does it rule out the DI unit? Probably not - I assume it can fail such that one of the coils dies before the others.
Could it be an injector problem?
Any more ideas out there?
04-23-2003, 05:24 PM
If you say disconnecting injector 2 doesn't make a difference then. You could try using a Injection cleaner. Just poor it in the tank when it's half full. And do some heavy duty drivng till the tank is almost empty. Then try if it makes a difference.
Or indeed change the DI.
04-23-2003, 06:07 PM
To confirm it is an injector problem, you could swap No.1 and No. 2 injectors and repeat the test. If the problem moves, then it is an injector problem. However, since the exhaust smells of fuel, it sounds more likely that the fuel is being squirted, but not being lit. This would suggest an ignition problem (or a mechanical problem leading to little or no compression, but let's not go there for the moment http://www.saabscene.com/forum/images/smilies/eek.gif ).
04-23-2003, 06:11 PM
P.S. a quick calculation tells me we might be discussing a 1994 model here. Engine size? Turbo or non-turbo? It all helps. As we narrow down the problem, the subtle differences between models might be significant.
04-23-2003, 07:07 PM
Have you tried swapping the ignition leads about so that the one for cyl 2 is moved elsewhere. The when you remove the 'new' one on cyl 2, are the results the smae?
Hope I'm not talking ar5e. I am not yet familiar with DI but that is what I would do on normal ignition stuff.
04-23-2003, 07:18 PM
Originally posted by bambo:
Hope I'm not talking ar5e.[/b]Perfectly sensible suggestion, but this wouldn't work with DI as there are no plug leads. DI is the system where each plug has its own ignition coil sitting on top.
04-24-2003, 04:03 AM
apologies for not telling you what the car is, which might make a diagnosis easier!
It's a 1994 Aero 2290cc turbo.
The way the car is running at the moment, and with almost a full tank of petrol I don't think I can go down the injector cleaning route just yet. But, I had already decided that it would be a good idea to swap the injector from cyl 2 to somewhere else and see if the problem followed it. Something for the weekend I think.
However, I'm still supicious of the DI because of the petrol smell in the exhaust and the blacker plug in that cylinder.
Anyway, thanks for your continued help!
04-24-2003, 05:42 AM
How about swapping the plugs over between cyl 2 and another working cylinder ?
04-24-2003, 05:56 AM
Not withstanding the excellent advise given above, a misfire and 9 year old DI cassette on 136k miles would lead me to believe that if it's not the DI at fault, it will be before long as most seem to pack up at the 100k-140k mark.
04-24-2003, 06:07 AM
My money's on DI-
Ben, your car will be Trionic, which is actually relatively insenstive to air leaks on the intake as it has a MAP sensor rather than AMM.(I know, I forogot to tighten up the rubber elbow to the inlet manifold and then had it blow off during max boost whilst overtaking http://www.saabscene.com/forum/images/smilies/eek.gif but the engine carried on happily, just (a lot) less http://www.saabscene.com/forum/images/smilies/fawlty.gif ).
The petrol smell indicates unburnt fuel. If it were a lambda problem, you would probably get a check engine light due to rich running on all cylinders. The single black plug and injector disconnection test certainly focuses down on no 2 cylinder, and a lack of combustion.
The next step is certainly to get a replacement DI to try. The motorway cruising symptoms you speak of are typical of a DI on it's way out.
04-24-2003, 06:55 AM
Thanks Guys. The simplest thing would certainly be the DI, so all I need is a fully functioning DI-equipped Saab to pay me a visit so I can try it out because the car really isn't driveable as it is, but, if push comes to shove I may have to go somewhere to try one.
Anyone here with Trionic 5 close to Ben? I am not passing that way anytime soon, otherwise you'd be welcome to try mine.
04-24-2003, 07:57 AM
If you can get as far as my place over the weekend, I should be around.
04-24-2003, 08:20 AM
Thanks for the offer Mark. I don't really think I'd want to drive the car to Marlow, although from Winnersh it can't be much more than about 10-12 miles. However, what I could do is bring my suspect DI unit and see if it performs the same way on your car.
I still think it's worth my while checking the injectors. My dad seems to think that if the injector was stuck open or delivering too much petrol it might give similar problems to the cylinder not sparking and combusting. Unless of course people out there know otherwise!
When my DI packed up on my NG900T I had a similar symptom regarding the cut out/stutter on motorway driving. When it eventually failed it would not start from hot but by time AA man arrived it had cooled sufficiently to re-start but continued to mis-fire under power. When I went to local Saab dealer they said that with mis-fire on a DI car they always start with a new DI and work down. They also said that if new DI did not cure it, I was welcome to take it back to them again - no charge - can't say fairer than that so might be worth a 'phone call to local Saab parts counter and see if they would agree to that?(although with your mileage and age on it it might be worth changing anyway as already suggested) - New DI cured it and mine had only done about 70k miles in eight years.(about £130 last November)
04-24-2003, 10:55 AM
Thanks for the tip Mike. I might just give Reading Saab a call.
04-24-2003, 11:18 AM
sticking injectors are not that uncommon. I know of a Ferrari 355 engine that has recently been rebuilt because of this (about £10,000, before you ask). If the injector sticks fully open, it dumps so much fuel into the cylinder that it washes all the oil off the cylinder walls, resulting in very rapid wear to the rings and bore. If you are running in this condition (or with a dodgy DI) , then presumably the lambda sonde will cause the other three cylinders to run very weak in an effort to compensate. So probably better not to drive too far.
Let me know if you do want to try your DI on my car.
04-24-2003, 11:20 AM
I could by 3 "new" cars for 10 grand!!!
I may well be in touch re: trying my DI on your car - many thanks for the offer. Reading Saab want 185 quid and weren't very enthusiastic about having it back if it didn't sort the problem.
I'm out for the rest of the day now, but will be on again tomorrow.
Sorry to hear that Reading Saab not quite so co-operative as Canterbury Saab - Eurocarparts can also supply cheaper than Saab dealers and I believe they will also give 10% discount to members of Saabscene if you let them know when you order. - I got mine with 10% discount from Saab because I signed up to some owners club thingy they run and it gives 10% off all parts bought there.
04-24-2003, 06:52 PM
I have got a mate who lives in Wokingham and has a K reg Carllson, I'll try ad get hold of him and put you in touch.
04-24-2003, 06:57 PM
I have a mate who lives in Wokingham who has a K reg carllson.I'll try and get hold of him and put you in touch.
04-24-2003, 11:41 PM
check battery charge and alternator connections
04-25-2003, 04:09 AM
Thanks for that offer Anthony. If he could swing by Winnersh sometime that would absolutely fantastic. Well worth a pint or two for his time I'm sure!
I don't think there are any other electrical problems with the alternator/battery, everything else is working fine and the computer tells me the battery is being charged ok.
Bring on the Carly from Wokingham!
04-25-2003, 11:49 AM
Was the plug in cylinder 2 wet? If it was wet then it will be injecting fuel (when things like this happen you can imagine smells like petrol when they are not there).
But I would say a DI fault. Does it fire ok from cold etc or don't you know? These things are usually temp related, when hot they start to breakdown so they no longer fire when warm, easy way to sort it is to spray whatever it is with an aerosol to cool it down then see if it works.
Thats helped me many a time with dodgy crank triggers etc.