Saab 900 rough idle in D?

Here is the most common cause of surges and stalls at stops and low erratic idle speed and rough idle, it is the idle speed control air-bypass valve and throttle valve (IAC for short), They get full of gunk over the miles and cause idle issues (stalls, low idle) like yours,

Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, Remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

Edit - the only performance enhancement option I know of you can do that will not cost a fortune is improving the airflow to the engine. You can split the exhuast into two tailpipes and mufflers with a shop that knows what is doing by splitting the pipe from the engine manifold, and with better breathing get a slight performance boost of 10 to 15 horsepower.

Unfortunately, turbo charging is not an option from what I know of the older Saab engines since reinforcement is needed which you will not want to pay for.

Not sure what you mean the display acts freaky. Under what condtions?

Saab 900 S

in case you stated the recommend and checked the fifth injector(chilly initiate) and it sprays, --there is yet another element that aspects extra air to flow with all that gasoline. it really is a touch dicast piece with a rubber line that is going from the front of the airbox(study throttle body) to the lower back--bipassing the throttle. it truly is electronicly managed. even as it really is chilly you are able to look good by capacity of it. After it heats up it really is closed. Disconnect it- plug its wires lower back on and purely turn on the most important and watch it slowly close. If it received't flow replace it. playstation This bosh FI device replaced into very universal-VW rabbits had all of them maximum each and every of the Audi used it at one time or yet another-element is even as the aspects are in distinct places, the worry capturing is an same. stumble on a superior previous timer rabbit mechanic and he can worry shoot it immediately. (wait until eventually you try to modify the air filter out ha ha hee hee)