[bobsverts]

Misfire

Quick check: pull the distributor cap and check the 4 contacts for the plug wires for deposits. It there, clean off the deposits. Clean the end of the rotor button. Check the spark plug wires for arching. Check the 4 plugs for damage. This may reveal the source of the misfire. Both my verts developed misfires and deposits on the distributor cap contacts were the problem.

Fix: replace plugs, ignition wires, distributor cap, and rotor. Misfires usually come from these sources.

Let us know the final outcome.

 

[tobiastoft]

RE: Misfire

Thanks for the tip! I'll check the cap, wires and plugs later today.

Fingers crossed!

 

[cghag1]

Your apparent misfire could easily cause the spike in temperature that you saw. I know I would overheat if I had to run up hill on one leg rather than my usual two.:cheesy:

 

[Geoff Weeks]

Hey guys,


Anyway, I decided not to take any chances and called up AAA and had the car towed back to where we came from. The engine still starts and the car drives (I topped off the oil first), but it definitely doesn't sound healthy. There's a lot of vibration in low RPM's and it doesn't seem to be firing right. I had no problems before this happened.

Any ideas? The thing I worry the most about was the fact that the temperature went up when it happened.

Thanks,
Tobias

Wow, most drivers I come across keep driveing with the gauges pegged and the oil light on "cause they only have a few more miles to go" and then wonder why they do so much damage. Haveing it towed for running rough wouldn"t even enter their minds. But I guess you would rather be safe then sorry.

 

[tobiastoft]

@geoff Exactly - I'd much rather be safe than sorry! And I've already paid for that AAA membership so why not use it

@cghag1 Sounds very reasonable - I'd probably complain a bit too

@bob Unfortunately I won't be able to get to my garage today as planned - I'll try to check the plugs, distributor and wires some evening in the coming week. I'll let you know how it goes. I'm hoping that's the problem!

 

[S900t8v]

Hey guys,

First post in the forum and it's a sad one :

Yesterday my '91 900 Turbo Convertible (aut, 135K) decided to have a hissy fit.

I was going uphill (mild, but long hill) in about 30C weather and suddenly I felt the car losing power. The Turbo gauge dropped and the temperature gauge started climbing (it made it to about 3/4's to the top before I could stop). Anyway, I made it to the top of the hill where the nearest exit was. I drove off, parked the car and noticed that the engine was running very roughly. I switched off to let it cool while I was freaking out.

After we'd both cooled down a bit I checked the coolant which seemed fine (no traces of oil from what I could see) and proceeded to check the oil which turned out to be frighteningly low (just under the MIN mark), last time I checked it was 2 weeks/300 miles ago and it was fine. It's been about 1300 miles since last oil change.

Anyway, I decided not to take any chances and called up AAA and had the car towed back to where we came from. The engine still starts and the car drives (I topped off the oil first), but it definitely doesn't sound healthy. There's a lot of vibration in low RPM's and it doesn't seem to be firing right. I had no problems before this happened.

Any ideas? The thing I worry the most about was the fact that the temperature went up when it happened.

Thanks,
Tobias

Are you sure the oil was low, if you checked it just after driving it it would probbaly show low on the dipstick as it's all up around the engine and hasn't had time to run into the sump... check it after it's been switched off for 30 mins or whatever.

Perhaps you had a large vacuum leak form (a turbo hose blew off etc) causing the rough idle, the lean engine condition may have caused a temp increase but it is sometimes possible to panic and think normal gauge movement is a bad sign...?

I'd just give the car a thorough inspection for vacuum leaks etc...

It does frustrate me how low the oil can get before the oil light comes on, if it truly was that low you may have done bearing damage as generally by the time that light comes on the damage is already done.

Just look for vacuum leaks, check ignition components etc first.

 

[tobiastoft]

Are you sure the oil was low, if you checked it just after driving it it would probbaly show low on the dipstick as it's all up around the engine and hasn't had time to run into the sump... check it after it's been switched off for 30 mins or whatever.

Good point - I probably checked it too early after pulling over.

Perhaps you had a large vacuum leak form (a turbo hose blew off etc) causing the rough idle, the lean engine condition may have caused a temp increase but it is sometimes possible to panic and think normal gauge movement is a bad sign...?

I'd just give the car a thorough inspection for vacuum leaks etc...

I've gone through all hoses and none of them seem to be leaking or have popped off, but being a Saab novice I'm not sure if I've been thorough enough. Any particular ones I should be extra thorough with? It's also very likely that I panicked and over-interpreted things

It does frustrate me how low the oil can get before the oil light comes on, if it truly was that low you may have done bearing damage as generally by the time that light comes on the damage is already done.

Just look for vacuum leaks, check ignition components etc first.

I'm not sure if the oil actually was that low or not - the oil light never came on and when I checked the oil the 2nd time (after getting towed) it was just above the MIN mark. I'll check the ignition asap. I fired it up last night and while it stalled a few times when idling (from cold) it did run but sounded like it wasn't firing on all cylinders.

 

[S900t8v]

pull your plugs

if one or two are wet suspect bad ignition components, if they are all tan/white/light brown then suspect a lean out / vacuum leak causing the misfire

you can pinch off all vacuum lines running off the intake manifold and see if there is a change.

Often splits in silicone hoses running from turbo to intercooler or intercooler to throttle body.

The splits can often be the type to only open up under boost, and so sometimes it's necessary to remove them and bend them and carefully inspect them. You could also try just tightening up the clamps on everything, ensure the rubber grommets in the intake manifold are not cracking etc.

 

[scantar]

My bet would be on a hose being knocked loose. Do you remember what you were doing at the moment things changed? Like did you try and pass someone on the hill or give it an extra push of the pedal? If you were boosting, even a bit of an acceleration can pop an old hose off a fitting. Did it trip the CEL?

 

[tobiastoft]

Thanks S900t8v and scantar!

I was overtaking someone going uphill (definitely bosting) and the first thing I noticed was that the turbo gauge dropped a few mm's and then dropped another few mm's 20-30 seconds later. At that time the car had lost a lot of power and ran rough. I guess it could be a hose then? It didn't trigger the CEL (or any other lights for that matter).

 

[scantar]

Thanks S900t8v and scantar!

I was overtaking someone going uphill (definitely bosting) and the first thing I noticed was that the turbo gauge dropped a few mm's and then dropped another few mm's 20-30 seconds later. At that time the car had lost a lot of power and ran rough. I guess it could be a hose then? It didn't trigger the CEL (or any other lights for that matter).

Boom baby. I'm going to double down on the popped hose bet. In fact, if it didn't shoot the CEL I'll say to check the boot at the intake.

 

[anjum]

It does frustrate me how low the oil can get before the oil light comes on, .

It doesn't measure oil level, it's a low oil pressure warning light. By the time it comes on you need to rebuild at least your oil pump and bearings

 

[S900t8v]

It doesn't measure oil level, it's a low oil pressure warning light. By the time it comes on you need to rebuild at least your oil pump and bearings

I'm not an idiot, I know it's a pressure light hence why it's after the pump and not in the sump. I was saying that by the time the oil level is low enough to cause pressure problems AT the oil pressure sender unit (which is directly after the pump ) the bearings have often already been starved of oil.

 

[tobiastoft]

I fiddled around with it this evening, trying to find a hose that had popped off or a leak somewhere. Unfortunately I didn't manage to find anything – I might just have missed it though, it was getting dark, but I believe I was fairly thorough.

As I couldn't find anything leak-wise I proceeded to change my spark plugs. The old ones were a bit manky and one of them was white-ish (see photo). None of them were wet though. Changing the plugs didn't really do anything, except that the engine ran a bit smoother (at least I think it did), it's still not smooth though. It was getting too dark to check the distributor cap, so I haven't done that yet. The wires seem to be in good condition.

I also recorded some video so you guys could hear it – it sounds a bit like a cold diesel engine. The video doesn't really show anything (I'm just moving the camera around using the LED as a flash light).

Video: http://www.flickr.com/photos/tobiastoft/7541182216

Any suggestions? Does the sound tell you anything?

 

[tobiastoft]

Hey guys,

I posted a reply last night but it's waiting for approval from a moderator (it's got a link to a video in it, which I'm guessing is why it's being held back).

Anyway, I've been trying to find leaks and popped-off hoses but without luck. Everything seems to be pretty tight. Would there be any hoses that aren't obvious or hidden from plain sight? I felt my way around last night, but it got dark pretty quickly and I haven't received my Bentley manual yet so I'm a bit clueless at the moment

Also, I noticed that sometimes when idling it'll sound normal for a few seconds and then drop back to the diesel-like sound. Could that indicate something? It's got about half a tank of relatively fresh (one week old) "Premium" (91 oct.) petrol in it, so that shouldn't be the problem.

In my held-back post I've included a bit of info about the spark plugs I changed last night (old ones were nasty) and a video where you can hear the engine run, hopefully it'll be up soon.

Cheers,
Tobias

 

[tobiastoft]

A small update

I managed to check the distributor cap and rotor this evening before it got too dark and it was nice and clean. I also made sure that my Turbo gauge moves when I rev the engine, it does and when it idles it sits around 25% (about 5-6 mm below the white dot). I poked around and pinched some hoses (the ones pinchable by fingers) while it was running and nothing really happened. It's fairly stable when it idles (~900 RPM), it just sounds like an old diesel engine.

When I left the garage I noticed that it had sprayed a bit of water from the exhaust, but I'm guessing that's just normal condensation.

Is there anything else I can do to try and diagnose what happened? I'm hoping the moderators will approve my comment with the video soon, so you can hear what it sounds like.

 

[tobiastoft]

Today I borrowed a timing light from a friend and verified that at least all of the ignition leads are getting power. I took out all the (new) spark plugs and checked them after running the engine for a few minutes and the three of them looked like they'd been "in action" while the last one looked remarkably clean. It wasn't wet or anything, just clean and shiny - don't know if it means anything.

I went through all the hoses again and checked the vacuum bushings and the plastic nipples and they all looked fine. I tightened things up a bit but to no effect.

I'm running out of ideas now - any help would be greatly appreciated

 

[scantar]

That second plug in your picture has an awfully lean burn look to it. the next two are just...well...really carpy looking.

The deiseling sound at idle is disturbing. If you are absolutely 100% sure that all the boots and hoses are tight (checked by yanking and pulling and tightening all the clamps) then I would start to see about the electrics...starting with making sure the main grounds are tight and clean and that the alternator ground is tight and clean.

 

[scantar]

BTW, you are NOT going to really see signs of turbo boot leaks at idle. As I have learned, boot leaks happen when the boosting exposes them by blowing them out, unlike a vacuum leak which generally shows up at idle (high vac situation).