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Discussion Starter #1
So I have this issue with my 900 where when the engine is started and its completely cooled from the last drive it will not idle correctly. It will start and rev up to 1700 then decrease to 800ish normally where it will either stall or come very close to stalling then rev back up to 1700 and then rev back down and so on until the engine is warm. I have cleaned AIC which helped some, i might re clean it because it did help so maybe i just didn't clean it enough. The turbo bypass valve has been replaced. Someone said it might me the AMM or O2 sensor but why would that only affect the engine when its cold? I want to get this fixed before winter because come winter it might have some real issues starting when its really cold out :confused:
 

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I have experienced the following....................

TPS - Throttle position switch or fine adjustment and or throttle body clean.
TPS needs to indicate to the ECU throttle plate is in the Idle position.
Throttle body can get gummed with oil and sludge which may prevent the plate closing correctly and acting the switch to put the ECU in the right mode.

See Bentley for fine adjustment.
 

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cold start sensor faulty..situated between 2-3 cyl on inlet manifold, try joining the wires on a cold start to see if that forms the circuit and it works ok
 

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cold start sensor faulty..situated between 2-3 cyl on inlet manifold, try joining the wires on a cold start to see if that forms the circuit and it works ok
It's between the injectors. NOT the knock sensor on the block!
 

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any luck? I started my car today, and the rpm gauge went from 800 to 1600 and back down, up again, etc. then the car would die. I let this happen 2 - 3 times. I was worried, so didnt allow the engine to warm. I've noticed that my car has smelled "gassy" recently, like the fuel hadn't been fully combusting, but it had been running ok till now. I was thinking that it was my AMM. I recently added a can of octane booster, that a friend had given me. I am planning a road trip, so I obviously need to get the car running before that can happen.
 

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Discussion Starter #8
I cleaned the throttle body but that didn't do anything but still a good 10min maintenance job if you have carburetor cleaner
have not tried the messing with the TPS
BUT a saab speciallist told me that 98% of the time it has to do with adjustment of the AMM hes intrustructions are as followed
"to put a volt meter on the O2 sensor, and then to turn the adjusting screw on the AMM until the reading is fluctuating around 0.5 volts. This is the way to do it and may solve everything. You can read step by step how to do this in the manual, it is easy but you should have a cheap analog volt meter, not a digital one"
if you get no reading from the O2 sensor that needs replacement also, just some trouble shooting; i havent done this but if it works tell me. Lastly is your idling problem only when the engine is cold then when it heats up it is fine?
 

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Air Mass Meter adjustment should not affect much when the engine is cold. That old system is working at more-or-less default settings until the O2 Sensor starts controlling things.
Try adding a 100 ohm resistor to the NTC (temperature sensor) circuit. Use a jumper wire to experiment with higher or lower resistance levels. A variety of resistors costs peanuts.
Altering that circuit to simulate colder conditions will change the default setting. Be sure you've eliminated all the usual suspects before you start trying to outwit the ECU.
This simplistic fix only applies to the earliest LH systems. Don't try this on later models.
 

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I hope the NTC fixes it for you but I don't share the diagnosis.

1987?
Turbo?
Metal AMM body?

ECU will be LH 2.2..........it is primitive and dumb but robust.
LH2.4 uses same switch set up.

Accurately mark the current location of the throttle stop screw.
Turn the throttle stop screw a full turn, ANTI -clockwise......re-secure the lock nut. Let engine get cold.
Try to start engine cold.

See if there is any change.........if not,
1. put the screw back where it was.........
2. Come back here and hurl abuse at me.

I used to have a LH2.2 EMS.........it was the first fault I ever struck with the car, the day AFTER I bought it.
I could replicate it at will simply by removing the TPS plug.
 

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any luck? I started my car today, and the rpm gauge went from 800 to 1600 and back down, up again, etc. then the car would die. I let this happen 2 - 3 times. I was worried, so didnt allow the engine to warm. I've noticed that my car has smelled "gassy" recently, like the fuel hadn't been fully combusting, but it had been running ok till now. I was thinking that it was my AMM. I recently added a can of octane booster, that a friend had given me. I am planning a road trip, so I obviously need to get the car running before that can happen.
Hi All,

It seems like my problem was the octane booster. I drained the tank (half full) and siphoned fresh gas into it, and my problem is mostly gone. I am getting the occasional fluctuation on the speedo and jerkiness, but its much better. The octane booster could have been 15 years old, but I didn't think that it could go bad. Maybe the Saab engine can't work well with the boosters? I have 6+ gallons of that gas mixed with booster left. I want to use it, but I don't like putting that stuff back in the car. Maybe I'll leech it off slowly. I think when I tried to burn the booster off at first, I may have killed the catalytic converter, something was smoking back there quite a bit. It's probably time I replace the fuel filter, also I'm wondering if the gassy smell I noticed before I put this stuff in means that I need to change my 02 meter?
 

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octane booster looses quality bad the same as petrol, it might be in a sealed tin but jusr detiorates like most things
 

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Hi All,

It seems like my problem was the octane booster. I drained the tank (half full) and siphoned fresh gas into it, and my problem is mostly gone. I am getting the occasional fluctuation on the speedo and jerkiness, but its much better. The octane booster could have been 15 years old, but I didn't think that it could go bad. Maybe the Saab engine can't work well with the boosters? I have 6+ gallons of that gas mixed with booster left. I want to use it, but I don't like putting that stuff back in the car. Maybe I'll leech it off slowly. I think when I tried to burn the booster off at first, I may have killed the catalytic converter, something was smoking back there quite a bit. It's probably time I replace the fuel filter, also I'm wondering if the gassy smell I noticed before I put this stuff in means that I need to change my 02 meter?
My problems come back, I'm going to start my own thread...
 

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1992....2.1l?
LH2.4.2

Sounds the AMM in your case..........Have you checked the ECU for any codes?
 

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All you need is a paperclip or some wire and a switch...........and watch for the flashing Check Engine light
If I remember correctly,Townsend's Saab site has a write up about it ..........
 

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this is link.......
 
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