Just changed oil pressure switch, and now oil light comes on, and other things.

I've had a 1999 9-5 for about a month now. I bought it and drove it 2000 miles home, and it ran great, with two problems--a Check Engine light, and an oil leak. The CEL was nothing--I changed the fuel and air filters, and it went away.

After a lot of cleaning of oil off the engine, I figured the oil was coming from the oil pressure switch, and while doing research, I also learned of the horrors of sludge, so I decided to hoist the thing on a lift (I'm a bookkeeper at a tire shop, so I can use the lift) and knock both problems out at once. Some cursing ensued, but basically I got it done, with a little help. I changed the switch, dropped the oil pan, cleaned the filter and pan, and got it back together. I did screw up on the gasket maker, using the forbidden silicone, and that's a culprit, but not sure it explains enough.

There was a very little sludge in the bottom of the pan. No metal. The filter wasn't clogged. The inside of the engine from below looked good, with maybe some sludge around the timing chain. In other words, pretty good shape.

Also, I had done a compression test before this, trying to find the oil leak (thinking blow-by), and it came out well. I had 205 in the first three cylinders and 190 in the last. The car has 140K on it.

Point is, it was in good shape, running smooth, no smoke, and everything mostly fine up until the moment I changed the oil and the oil pressure switch. In fact, immediately after I got it together (or the next day, but before I drove it anywhere else) I took it two miles up the road and got an inspection sticker.

On the way back, the oil light came on. It came on when I took my foot off the gas, went off when I gassed it. It also started idling a little rough, like it was about to die, and at one point it seemed to be loping, like a vacuum line was off--or maybe it was just idling low enough that it was sputtering. It had never done this before, and I'd driven it for a month and about 3000 miles total. When I turned the AC off (so I could hear it better), it started idling smoothly again, but the light still flickered on and off when I idled.

I drove it the remaining mile or so back to work and parked it. I checked the oil level, but it was maybe a quarter of a quart low. I crawled under it, and it wasn't leaking oil anymore. I checked the vacuum hoses where I and my buddy reached around in the engine compartment to get the starter bolt off, but couldn't see anything right off. I let it sit a couple of hours--no oil on the ground or engine (so at least that's fixed). I started it again, and it idled perfectly with no light. I just let it idle for a while, and finally, a little after the temp gauge reached its normal spot, the light came on and it started the rougher idle again. I gassed it hard, and a gray smoke came out of the tailpipe. That had never happened before, either, and I had checked. It doesn't smoke at startup, it only smoked like that after I changed the oil and oil pressure switch and it got up to operating temps.

Sorry so detailed, but thought it might help. I'm open to the idea that there could be a couple of things wrong, but since none of this was happening when I shut it off before the repairs, and all started right after, I can't see how it's not connected. I'm thinking either we knocked something loose, the pressure switch is bad, the old pressure switch was bad so I'm just now getting a true reading, although this doesn't explain the idling or the smoke (the oil lamp light did come on before ignition as it's supposed to before I changed it), or the oil (Mobil 1 5w-30) is somehow too thin--I think maybe the other guy tried to hide the oil leak by using STP or something to thicken the oil, since it seemed more viscous when I drained it than what I put in. Or of course the silicone could have already chunked into the sump and clogged the filter, though it seems too soon for that to be the issue, and I didn't go crazy with the sealant, so there isn't likely to be enough in it to clog the filter, anyway (I do plan to drop the pan and use the right stuff, either way).

I've also seen a couple of comments across the Nets that others had oil lights come on after changing the OPS, but I've never found a universal conclusion to these. Some say it just went away after a learning period for the new switch. Might happen on mine, but I'm timid about running it now because of the silicon, even knowing the strainer is otherwise clean.

Again, sorry so detailed, that's just the only way I know how to be. :) Any help or suggestions are greatly appreciated.

Welcome and great job on the detailed post. You can never have too much information when it comes to things like this.

Did you read the OBD-II codes? I am just curious what the CEL was about as it seems unusual new fuel and air filter fix a problem.

Quote:

---

Originally Posted by Wulf

Did you read the OBD-II codes? I am just curious what the CEL was about as it seems unusual new fuel and air filter fix a problem.

---

Yes, or rather, my mechanic buddy did. There were two, and I don't remember them. One was that the fuel was burning too rich, and the other was something else like that. As soon as he read them he told me to change the filters, and that fixed it. They had to be the original filters--the air filter was so dirty you could shake it and create a dust storm, and the fuel filter was so corroded into place I had to knock it loose. Strange, considering that so much else on the car seemed well-maintained. The hoses and belts, for instance, are all fairly new looking. Of course, that might just mean that something had visibly failed so they replaced them all at once.

I've done a bit more googling, and one site where a similar case was discussed said that 30 weight oil would be too thin for fully synthetic oil in a 9-5, and that could make the light come on. I used 5w-30. Could it be that simple? I hate to waste 30 bucks of oil (although it's so new I could just catch it and use it in my other car, I guess) on a guess, but then again, that's cheaper than a lot of guesses I'd be doing.

It makes sense. When the oil gets hot, it gets thinner, and maybe doesn't seal around the pick-up tube as well, and maybe gets pushed past those low-friction pistons too easily, making it smoke only when hot, not when it's cold. Still, seems too simple. Could the difference between 30 and 40 make that much difference?

And I just thought of the pick-up tube in the pan. The O-Ring on it wasn't bad, so I didn't replace it. It was still a very snug fit to put back together. But maybe too-thin oil and a slightly worn o-ring could be enough when the engine gets hot? I'm tempted to just drain the oil, drop the pan, put in a new O-ring and seal it with the anaerobic stuff, and put in heavier oil. The pan really isn't that hard to drop with a lift, and I've done it already so I know all the fiddly-bits that took me forever the first time. Could probably do it in an hour this time, since I won't have to scrub the pan again. Is that likely enough to be worth it?

With problems like this, it's often best to start somewhere and rule out anything that can be easily and inexpensively changed. A big problem is easier to solve when you split it up in smaller parts and correct those if needed. And as you mentioned, you don't get any further with guessing. :)

If the air and fuel filters were that ols and dirty, you wonder about the oil change intervals. Even though the engine doesn't look that dirty ont he outside of internal components, it's difficult to tell what the inside oil passages look like. Could you tell if it was he first time the oil pan was removed? Another test would be to remove the valve cover and see what it looks like under there.

5W-30 should be fine for the 9-5, according to Saab's specifications. It's difficult to say a 0W-40 oil will make a difference but it's relatively inexpensive to try. Mobil 1 5W-30 doesn't meet GM-LL-A-025 or A3/B3 specs (in the US, I assume that's where you are).


http://saabworld.net/attachments/f9/...ab-9-5-oil-gif

Well... That was fun, I guess. Just flushed the engine, dropped the pan again, cleaned the silicone gasket material, reassembled, and added 0w-40 Mobil 1. I thought for about an hour I had fixed it.

First, the pan had a few crispy black shards in the bottom, but no metal. Worse, though, the screen was partly clogged with something that I'm guessing was silicone. In less than five miles and maybe an hour total of running, the screen was between 30 and 50% clogged. The stuff was clear (not blue, like the silicone sealant I used), and kind of like thin shredded plastic, or almost like peeling skin. So I'm glad I checked that out.

I also replaced the O-ring on the oil pickup tube, then I reassembled with Permatex's anaerobic gasket maker, added the 0w-40, and started it up.

No leaks, everything was smooth. I idled it for about half an hour, and nothing happened. So I revved it to see if it was still smoking, and it wasn't. I revved it two more times, thinking I had fixed it. On the third rev, when it went back to idle, the check engine light came on, and a minute later, the oil light started flickering on again.

So, whatever was wrong got better with an oil change and screen cleaning, then came back an hour or so later (except maybe the smoke, but that could come back, too), after light use (mostly idling). The car had never done any of those things before I cleaned the pan and changed the OPS. I had it a month, I drove it in New York City stop-and-go traffic for a day, drove it 2000 miles back along the interstates for about 30 hours straight, and drove around Austin in 100+ degree temperatures for about a month. It smoked under the hood from the leaking oil the whole time, but the CEL never came on, the oil light never came on, it never pulsed while idling, it never smoked from the tailpipe.

So something I did with the oil pan or the OPS caused this.

Any ideas? I need to scan the CEL, and get an oil pressure check, I guess. Nothing I did fixed it, so none of the stuff I fixed was the problem, unless the anaerobic sealant could ahve done the same thing as the silicone, or the flush loosened stuff up that didn't hit the screen until after reassembly. That doesn't seem likely enough for me to drop the pan a third time without some evidence.

So these are my only ideas now. Bad new OPS--an oil pressure check might tell me; worn rings or seals or oil pump that the stuff the seller put in it covered up, but with the oil leak and the miles I drove it, at least half the oil was replaced before I dropped the pan, so it wasn't much thicker by the end; a clogged screen again, from the flush or the anaerobic sealant (though I was more careful this time, and I thought it wasn't supposed to break apart like the silicone, anyway); or something my buddy or I knocked loose or broke while trying to remove the starter and OPS. Or maybe the oil pump, but that doesn't seem right, since there was no hint of a problem with it before.

Know of anything related to the wires and vacuum lines around the throttle body and turbo behind the engine that could cause all of this? :)

And the PCV system seems to be the newest one--it has the GM hoses, though it doesn't have the little thermal blanket around the check valve. All that's the same as before the problem started, though I guess maybe a hose could have deteriorated with the thinner oil somehow. I've squeezed, but everything seems normal.

These cars have terrible oil pumps which have been upgraded back to the same units in use prior to 99. Looking at your problems I would get an oil pressure reading. It is not a hard job but you must replace both the housing and the pump if you need to go this route.

Could the oil pump cause the car to idle erratically? I could only think of two ways--one, the computer somehow senses low oil pressure and increases RPMs when it drops too low, or two, a bad oil pump drags the engine down further at slow speeds, making the engine rev to avoid stalling. The erratic idle and oil light have to be connected, because they started at the exact same time, and more importantly, because the oil light doesn't come on unless the engine is pulsing and at the bottom of its ebb. Sometimes the engine pulses without the light coming on, but the oil light only comes on when the RPMs drop below about 700 (usually lower, around 500), and go off immediately when the engine (on its own) revs back above this. Is that how it acts when the oil pump goes out?

Another thing--the engine speed when the light comes in is right about stall level. I can feel the car shudder, like it's about to die, and a couple of times when I've actually driven it and taken my foot off the gas, the power steering has gone out just as the oil light comes on, like the whole engine has died and then shuddered back on.

Is that how a bad oil pump acts?

The oil light going on at that low rpm is pretty normal. Spray your vacuum lines with some brake parts cleaning fluid and see if you get a surge and dont for get the line out from the bottom of the turbo.
Also, check these post out if you like
All of these issues you have all point to a Vacuum leak
http://www.google.com/search?q=9+5+i...=images&tbsare

Thus you down to finding the bad idle, Any car at 500rpm will light up the oil light. So congrats, you are almost home. Simple thing first. Get some throttle body cleaner and clean out the well w/o removing it. Use a toothbrush to get around the butterfly. If you get an improvement, remove it and clean it better. Make sure the O Ring is installed correctly around the top section of the intake . You will see a groove around the top of the TB Housing

Thanks, Mike. I pulled open the throttle body, but it was pretty darned clean, though I'm not sure what to look for. I toothbrushed it with some cleaner and got a thin layer of soot, but nothing much. I looked at and sprayed hoses until I was hyperventilating, and nothing surged. Actually, it looks like someone may have tried all this before I got the car, since the TB looked cleaned inside and a lot of vacuum lines seem new.

A couple more observations. The engine starts the slow idle speed when I've revved it up a bit, either driving or sitting still. When I take my foot off the gas, the idle drops way below normal, then pulls back up just as it feels like it's stalling. Sometimes it surges around for a minute trying to stabilize, other times it just goes right to normal. It does it every time, even when I'm slowing for a stop sign or speed bump going less than twenty to start with. It will do this sometimes while just idling in neutral, but usually only when the engine is coming down off a rev. So now I'm thinking it seems more like idle and speed control than like a vacuum line.

Also, the AC causes it to almost stall, and takes a few seconds to stabilize. I know there's a switch that's supposed to stabilize it more quickly than that. Also, when the radiator fans kick in, the idle dives and it lopes for a few moments. A few times I've even noticed the lights dimming as it dives, but I think that may be like the oil pressure, where the alternator has slowed too much. The battery is less than a year old (again, maybe the previous owners had the same thoughts on the same problems), but it is a Walmart brand. :(

One more thing--the spark plugs after only a few hundred miles have some carbon, so it's burning rich.

Any of that work into an "Aha!" moment? :) If not, no worries--you've pointed me in the right direction, now it's just a matter of hitting the target. Thanks.