91 Saab 900s check engine light troubleshooting?

Well, the honeymoon is drawing to a close. I finally paid too much money to the state so I can legally drive the new Saab. Today I took it across town for a meeting, and it ran just like it did when I brought it home (great!). As I arrived at my destination and parked, the check engine light came on. It was idling normally and I turned the engine off.

So the meeting ended and I returned to my car and started it up. Check engine light is still on, nice steady idle at about 1200 rpm. I pulled out of the parking lot to go home, and it started hesitating real bad. Like I was letting the clutch out without enough gas applied. This was in 1st and 2nd gear. At the first light I got to I took it out of gear and it tried to die on me, so it wasn't idling like it was. I had to heel-toe it to get it home without stalling. If I kept the rpms up it ran fine, power seemed to be as it was as far as I could tell.

I got home, parked it in the driveway, applied the parking break and let it idle. It promptly stalled. I restarted it again, CEL is still on, now idling happily at 1200 rpm again. Turned it off and restarted it, same results- happy idle at 1200 with the CEL light on.

So I took a couple slow laps around the block, stopping periodically and it didn't stall or hesitate again. CEL is still on.

My owner's manual says this about the CEL light:

I don't have a Bentley manual yet, so I turned to google. It led me here: Linky to Saabcentral

In this image from an 87 (the closest I could find) this is the LH diagnostic plug:

On my car (the 91) the closest thing I could find in the described area (from the link) with the same wire color going into it is the middle connector in this image:

If this is the correct diagnostic port, that same Saab forum post says to use the diagnostic procedure described in this link: PULLING CHECK ENGINE CODES 2.4 LH

Am I barking up the wrong tree here? Does anyone know? I can't find any kind of an OBD port on the car, probably because there isn't one.

Any input would be appreciated!

I'll look it up in my Bentley manual when I get home later. This has a 2.1 NA engine with EZK ignition, correct?

The instructions on that website are exactly what you need to follow. It's OBD1, so you won't find anywhere to plug in an OBD2-style scanner. The blinky light will tell you everything you need to know after the switching procedure.

Thank you HappyAndy, I really appreciate it! There is no rush by any means.

Yes, 2.1 NA engine, I'm not sure of the ignition. I'll go out and check in a minute...

HappyAndy wrote: I'll look it up in my Bentley manual when I get home later. This has a 2.1 NA engine with EZK ignition, correct?

And I thank you sir!

This is new territory for me, I'd rather not cause a meltdown!

pointofdeparture wrote: The instructions on that website are exactly what you need to follow. It's OBD1, so you won't find anywhere to plug in an OBD2-style scanner. The blinky light will tell you everything you need to know after the switching procedure.

mine used to throw a light every so often and then run like utter crap until it decided to run right again.

Really?

Did the light clear itself?

Maybe this one of the Saab quirks I've heard of...

mad_machine wrote: mine used to throw a light every so often and then run like utter crap until it decided to run right again.

If the light is coming and going, something is wrong and you should find out what it is, the ECU just isn't seeing the issue all the time, or the severity is varying. Could be as straightforward as a bad MAF connection, and the code will point you in the right direction. With how simple it is to check, settling for "it just does that sometimes" is kind of a silly thing to do. None of my 3 classic 900s ever did that in the cumulative 60k or so I had them for, so I wouldn't say it's a Saab thing by any means.

Also, all you are doing to trigger the code reading procedure is completing a ground circuit in a pattern to throw the ECU into code display mode. Not a dangerous procedure unless you somehow confuse the correct terminal with one that's supplying 12v+...

From what I've seen so far the light is staying on.

pointofdeparture wrote: If the light is coming and going, something is wrong and you should find out what it is, the ECU just isn't seeing the issue all the time, or the severity is varying. Could be as straightforward as a bad MAF connection, and the code will point you in the right direction. With how simple it is to check, settling for "it just does that sometimes" is kind of a silly thing to do. None of my 3 classic 900s ever did that in the cumulative 60k or so I had them for, so I wouldn't say it's a Saab thing by any means. Also, all you are doing to trigger the code reading procedure is completing a ground circuit in a pattern to throw the ECU into code display mode. Not a dangerous procedure unless you somehow confuse the correct terminal with one that's supplying 12v+...

1200RPM idle makes me think there's a vacuum leak somewhere, but I'm not sure if that will pop a CEL on an LH system. Maybe check for leaks first. There are several tee fittings with hoses that come off the intake, and a long line that crosses over the back of the engine bay if I remember right. Haven't really looked at it in a few months, though.

That Townsend page is the same one I used as a reference troubleshooting LH injected 9000s back in the early 14th century .

I just noticed his page says the 89+ 900 has the connector under the back seat. I'll go dig into my car after work and see if it has one there.

I agree with the above comments about it sounding like a vacuum leak. Sometbing you can check without a manual or tools. Tbe lines are old, and of a European rubber. They don't hold up well.

Hopefully you will find a simple break.

You can pull and cap a line at a time on the intake manifold to find which line(s) are affecting the engine.

This is the excuse you were waiting for to buy a manual. Maybe two manuals.

Foxtrapper and XLR99, thank you for the tips!

I had an extra hour today so I went out to poke around with the Saab. After pulling the rear seat I found a black connector (with no cover) in the center of the seat. Maybe this is were I get the codes from.

Here is a side view of the connector. I can't really move the wires to see the exact colors but it seems to match the description from the 14th century website I listed earlier :

As for the vacuum line idea, I did feel around as much as I could on the lines coming from the intake manifold. One goes to the valve cover, I pulled it out (it's pretty loose anyway) and had no effect on idle. The others seemed pretty solid. Then I noticed this guy, and remembered the PO did put a new alternator on. Maybe he didn't push this line back on all the way?:

I pulled the line off and the engine stumbled and started to idle real rough. After pushing it on all the way the idle settled at 1k rpm cold, nice and steady. I took another few laps around the block to bring it up to temp. Back in the garage after this the idle was nice and steady at about 900 rpm.

This weekend I will try to actually get the error codes and see if I can reset the CEL. Maybe I got lucky!

You could just pull the negative battery terminal for awhile to clear the light and see if it comes back.

foxtrapper wrote: This is the excuse you were waiting for to buy a manual. Maybe two manuals.

A Bentley and which other one? Haynes?

Excellent idea Evan, thank you! I think I'll try that and see what happens.

EvanB wrote: You could just pull the negative battery terminal for awhile to clear the light and see if it comes back.

CELs on OBD1 cars do not stick around long..

Nice! I love free fixes! That's the long hose that goes across the car. Looks new, but if you keep having issues, follow it along and make sure there isn't a break somewhere further back. Mine had been spliced into an old piece where it met the firewall, and was leaking there.

Yes, that is the one! This went down into the passenger side fender and then went somewhere... I'll try to trace it the rest of the way and be sure it isn't leaking somewhere else.

Thanks again for all the help!

XLR99 wrote: Nice! I love free fixes! That's the long hose that goes across the car. Looks new, but if you keep having issues, follow it along and make sure there isn't a break somewhere further back. Mine had been spliced into an old piece where it met the firewall, and was leaking there.

Just reset the light by disconnecting the battery. I had to do it a couple times on my Volvo of the same vintage and it always worked as long as I had actually fixed the problem. If not, it would come on again.

I'll also point you to saabcentral.com and saabnet.com. Both have wonderful forums that might actually be more active than this board. I will say though that the older cars get more attention there than the newer (so you're in luck!).

I was thinking I'd try to pull the code for the sake of learning how to do it, then reset it by disconnecting the battery. My fingers are crossed!

And I just joined saabcentral.com an hour ago. I'll be sure to join saabnet too!

asoduk wrote: Just reset the light by disconnecting the battery. I had to do it a couple times on my Volvo of the same vintage and it always worked as long as I had actually fixed the problem. If not, it would come on again. I'll also point you to saabcentral.com and saabnet.com. Both have wonderful forums that might actually be more active than this board. I will say though that the older cars get more attention there than the newer (so you're in luck!).

asoduk wrote: Just reset the light by disconnecting the battery. I had to do it a couple times on my Volvo of the same vintage and it always worked as long as I had actually fixed the problem. If not, it would come on again. I'll also point you to saabcentral.com and saabnet.com. Both have wonderful forums that might actually be more active than this board. I will say though that the older cars get more attention there than the newer (so you're in luck!).

Tell me about it. GM SAABs get almost no love at all. That is starting to change, s l o w l y.

Disconnected the battery and the code is clear, no more CEL.

paranoid_android74 wrote:

foxtrapper wrote: This is the excuse you were waiting for to buy a manual. Maybe two manuals.

A Bentley and which other one? Haynes?

One is enough: the Bentley, which is an abridged version of Saab's actual factory manuals (transmission rebuilding is omitted, as well as some wiring diagrams that you'll most likely not miss, plus some other stuff). Don't be worried about "special tools," as there are few that you can't DIY easily.

IMHO, Saabnet has the edge on Saabcentral for c900 info, despite its design and rules that some find unusual. Search doesn't work well there, so go to Google and try this instead:

"search terms here, including the quotes" site:http://www.saabnet.com/tsn/bb/900/

Regarding c900 check engine lights: it's not uncommon to get them when the O2 sensor reports back bad news. But pulling the codes isn't often useful: the code you pull this weekend will probably tell you that the engine ran lean, but you have no idea why and the ECU won't know, either. Maybe it's from owning these cars too long, but I don't bother checking codes. Most of the issues I've had with CE lights have been vaccuum-related or due to failed Bosch fuel-system parts...

Once again, excellent advice- thank you!

Driving home this evening the check engine light came back on. The vacuum line I found yesterday hasn't moved at the fitting, so something else is going on. I'll try to find time to dig into it tomorrow.

procainestart wrote:

paranoid_android74 wrote:

foxtrapper wrote: This is the excuse you were waiting for to buy a manual. Maybe two manuals.

A Bentley and which other one? Haynes?

One is enough: the Bentley, which is an abridged version of Saab's actual factory manuals (transmission rebuilding is omitted, as well as some wiring diagrams that you'll most likely not miss, plus some other stuff). Don't be worried about "special tools," as there are few that you can't DIY easily. IMHO, Saabnet has the edge on Saabcentral for c900 info, despite its design and rules that some find unusual. Search doesn't work well there, so go to Google and try this instead: "search terms here, including the quotes" site:http://www.saabnet.com/tsn/bb/900/ Regarding c900 check engine lights: it's not uncommon to get them when the O2 sensor reports back bad news. But pulling the codes isn't often useful: the code you pull this weekend will probably tell you that the engine ran lean, but you have no idea why and the ECU won't know, either. Maybe it's from owning these cars too long, but I don't bother checking codes. Most of the issues I've had with CE lights have been vaccuum-related or due to failed Bosch fuel-system parts...

If there is a haynes, get it as well. Bentley is excellent, as mentioned above. But a haynes will hold your hand better when you're learning.