Saabscene Saab Forum - Saab Technical Information Resource banner
1 - 8 of 8 Posts

·
Registered
Joined
·
79 Posts
Discussion Starter · #1 ·
My 98 CSE is having a strange idle problem. It sometimes is sticking at around 2k rpms then will slowly drop to 1200 rpms and will stay there for a bit then drop really low and bounce up to the normal 950 rpms where it used to stay all the time. Sometimes it skips the 2k part but you can feel when changing gears that it kinds of shoots up a bit before falling when the clutch is pressed. Also, I have been steadily losing mpg from 24+ mpg when I got the car a year ago to now about 21 mpg. I was thinking it might be a vacuum problem so I am going to replace all the vacuum hoses with new silicone hose sometime this week. Any other suggestions would be helpful. Thanks in advance.
 

·
Registered
Joined
·
14,305 Posts
As your car is a 98, it shouldn't suffer from economy problems with leaking hoses as it uses a MAP sensor, which measures the inlet manifold pressure to compute the fuel required rather than an airflow meter. 98 is also quite young for hoses to be failing.

I'd suspect the IAC or idle control valve. They get gummed up from time to time and need cleaning out. This would give you the erratic idle and if it's sticking open on overrun, also have an effect on your fuel economy.

Take it out, and give it a good blast with carb cleaner, and see what happens.
 

·
Registered
Joined
·
14,305 Posts
Sorry, my mistake first time, it's called the AIC valve.

Anyway, from memory it lives in one of two places- either under the throttle body or on top between it and the rocker cover. It's an aluminium housing, about 1½" in diameter and 3" long. It connects to two hoses, each about 3/4" dia plus an electrical connector. It's purpose is to bypass the throttle butterfly when it is closed, allowing air in. One hose will connect to the throttle body on the manifold side, the other on the inlet.

BillJ's website lists the procedure here
 

·
Registered
Joined
·
79 Posts
Discussion Starter · #6 ·
Ahhh no wonder I couldn't see it. That ****** is buried deep in there. I should have thought to check BillJ's site. Thanks again.

Oh yea, is erratic idle a symptom of a failing di cartridge as well?
 

·
Registered
Joined
·
2 Posts
I have recently had exactly the same problem with my 1991 CD. The fuel pump went so I had it replaced, once the new one had been fitted I had erratic idling problems as you described. I took the car back to the garage and they could not find the cause of it. Needless to say I found a great SAAB mechanic who plugged it into one of the SAAB diagnostic computers and he found a whole load of temporary and permanent errors within the onboard computer. He deleted all of the above errors. When we started the car it ran like a dream straightaway. The only thing I have noticed since the new fuel pump has been fitted is that my fuel consumption has gone up from approx 28mpg to 23mpg. I do not know whether the pump can be tweaked to enable the engine to run leaner.
For anyone interested the mechanic is Rowan Bott of South East SAAB based in Tunbridge Wells. He used to work for SAAB City, London E1. Contact him on 01892 529000.
Hope this helps.
 
1 - 8 of 8 Posts
Top