Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Saab 900 will not idle / run

I have a saab 900 which last year I added some old octane booster a friend gave me. He told me it would be fine, but after that, the car has not run. I’ve drained the tank, and I ran the gas through another car, which seemed to run ok. The car has passed a fuel volume test, i ran it after replacing the fuel filter. I’ve also replaced the rotor, plugs, cap, wires, and cleaned the AIC valve. On the AIC valve and checked it’s electrical resistance, it tested good. I added hose clamps to many of the hoses and lines. I searched for vacuum leaks. I have some photos and a video of the car and how it runs.

Unfortunatly the engine is not throwing any check engine codes. I tried checking some of the voltages at the fuel injection computer and ECU unit wiring, but didn’t find any problems. The car has Bosh LH 2.4.2 fuel injection. It also has an air mass meter. The car is supposed to default to running at a high 1000-1600 rpms when the AMM is disconnected ,however it would not start with the amm disconnected. Therefore I think the problem is something else.

I think it could possibly be a blown head or bent valve or something like that. I was thinking about getting an compression test kit and a timing gun, since I replaced the rotor and cap. I’m looking for advice on what I should check next?

You said it won’t idle/run, but that could mean a couple of things. It starts but then stalls? Or you turn the key and it just cranks and cranks but won’t fire up?

You did all of this stuff with the spark & fuel systems, but have you actually checked to see if things are working? The fuel injectors should be ticking (listen with a little piece of hose or stethoscope). You can shoot some starter fluid into the intake and see if that gets a hiccup out of it. You can use a spare plug or spark tester to check for spark.

By all means a compression test is never a bad idea.

If you look at the website you can watch a video of the car. It starts and then the idle goes 1000-1600-800-2500- 1200, until it eventually dies . Watch the video and you will see.

There is spark on each cylinder, I already tested for that. I did the fuel volume test to see if the fuel pump was working properly. I forgot to mention that I cleaned the throttle body and valve which leads to the intake with carb cleaner. This leads to the intake, and it definitely caused a hiccup.

I will try to check to see if I can hear the fuel injectors, thanks for that idea.

If I’m going to order a compression test kit, am I better off with something like OTC cylinder leak tester than a cheaper kit Equus Innova-Compression-Tester

I don’t have a very good internet connection - and even if I did I’m not sure I’d watch videos online. Someone else here will watch it, I’m sure. It sounds to me like you have a massive vacuum leak. For things like specialty auto tools that get occasional use you’re often better off with the free “loaner” tools programs via auto parts stores. What I would get right now if you want a super-useful diagnostic tool for not much $$ is a vacuum gauge.

I can get invest in a vacuum gauge. Unfortunately I live in an area where there is only a NAPA, and I’m not sure about a tool loaning program. I’ve searched for a vacuum leak, haven’t found any so far. There are also pictures on that site. Maybe someone will watch the video and comment, but so far you are the only person to comment. Thanks!

I bit the bullet & waited for it to load. Give a run down on the two lights on the dash. One is flashing, the other solid. What are they? Sounds like hell. Now I do think you want to check the compression, although for as bad as it sounds you’d be able to get indication of it on a vacuum gauge - and they just happen to be more versatile and cheaper as tools for a shade tree mechanic.

Now would be a good time to fill in all of the missing info. How many miles? What do you know about its history - including how its been driven and very specific maintenance info.

Octane booster, btw, is one of the silliest things to put in a car. Its not going to help anything or improve anything. That said, its unlikely to hurt anything. I think putting it in was a coincidence. But is there some reason that you put it in?

I put the octane booster in there since I had filled the car with 87 and its recommended to fill it with 89. I had it around somebody I had helped had given it to me and told me I should use it, so I thought it would be ok. Maybe it is a coincidence…

Regarding the lights, one is the SRS airbag, one is the parking brake light.

The car has 180k. Looking on amazon, a compression tester is ~23$ while a vacuum tester is ~18$ . Wouldn’t the compression tester be better? I can afford both, it would cost ~ 1/2 hour at the shop, or less…

I have some maintenance info from the previous owner, with records before that. It seems that these people had regular maintenance schedule preformed. Didn’t see anything that alludes to the issues I’m having now. The work I did on it was replace the front motor mount and I rebuilt the starter. I had first bought a used starter that didn’t work, then bought new from amazon and they sent me the wrong part. Finally I ordered a starter drive, and rebuilt the damn thing and put it in.

I ran it for 6 months after that, no problems. I haven’t personally run the car very hard. I replaced the coolant and switched it over to synthetic after I bought it. I’ve had it 2-3 years now.

Ordered a compression tester. Going to check compression on each cylinder Monday or Tuesday. I’ll post back then with the numbers.

hello i went to your website and reviewed it and there are somethings i like to point out i hope it helps

  1. the firing order is 1342 according to your diagram all the plug wires are firing early-one place on the cap
    3 should be plug 1
    4 should be plug 3
    2 should be plug 4
    1 should be plug 2

remove the cap on the lip of the distributor is a line that tells you what number one spark plug is

the four wire plug that sits near the starter where you found that cut red wire is for the CPS (crank position sensor) this will cause your car to die this is responsible for variable timming of the engine

that little coke can with the broken wire is a capacitor for the radio prevents electrical interference its connected to the outside of the distributor on one of the clips that holds down the cap to the bolt that holds the bracket that the coil sits in

the white and yellow wire in front of the engine on the head is the temp sensor

Hi, thanks for your help. Are you sure about the wiring order? Somebody else on the saab forum told me I was correct… I’ll have a look for the line that you mention, and maybe I’ll switch the wires around and see how it runs.

Thanks for identifying the cut red wire and the cut white/yellow wire. I’ve since repaired the wiring. I took a compression reading yesterday:

I got a compression reading yesterday. It looks like:

cyl 1. 200
cyl 2. 180+
cyl 3. 190
cyl 4. 190-

My friend read the gauge. I guess he meant a little over for + and a little under for -. He had trouble turning the ignition. I actually asked him to catch the numbers on each turn and so the full reading that he took was

cyl 1. 120-155-180-200
cyl 2. 90-120-150-180
cyl 3. 120-155-180-180
cyl 4. 120-150-180-190

I actually turned the motor 6 times on each cylinder, so it may have been a little too fast for him to read the gauge, since he only got 4 entries. Do my numbers check out?