AboutJerry Schwell Expertise Most anything about SAAB 900's 1990 and earlier only, except for automatic transmission info. Also, I have lotsa vintage parts.
Experience I have rebuilt many dozens of SAABS, from 1970's to 1990's.
Education/Credentials BSEE grad work in electronics and underwater acoustics.
Expert: Jerry Schwell Date: 5/22/2008 Subject: injectors
Question i have a'78 99,love it,starts fine but when i give it gas it sputters until warmed up. new plugs, wires are not arching, timing good. injectors?? my mechanic said they have a good spray patten...i cleaned them myself but still sputters.......
Answer Mike:
If I recall correctly, you have the mechanical CIS[K-Jetronic] fuel injection system on your SAAB. This works by measuring the airflow past a round plate attached to an arm which in turn is attached to a metering valve providing the correct amount of fuel in proportion to the airflow. The plates deflection is proportional to airflow. On a cold start condition, if there were greater plate deflection due to a certain airflow, this would mean a higher fuel-air ratio as required until the engine warms up. This is provided by the warm-up valve regulator, a squarish aluminum box with two lines going to it mounted near the radiator on the driver's side.
I BELIEVE THIS IS THE CAUSE OF YOUR PROBLEM, A WARN-OUT WARM-UP REGULATOR.
It works by providing a reduced back-pressure against the airflow metering plate, thus allowing for a greater deflection relative to airflow and thus providing a richer mixture (higher fuel-air ratio) as noted above.
This is caused by a bimetallic strip within the regulator losing a bit of stiffness with age and use.
I did an extensive investigation of this device years ago and came up with a simple, immediate fix. You can restore the stiffness of this metal strip by tapping inward a recessed steel post visible from the outside of the regulator box next to the electrical input plug very carefully...maybe only .01 to .025 of an inch. This recessed post is held in place by a friction interference fit and is about .5 inches in diameter. You should use a depth guage(caliper). The post is typically recessed by about .03 inches as factory calibrated. By tapping it inward, you are simply recalibrating it for age and wear.
Output pressure of the warm up regulator should be about 17 =/- 4 psi at 50 deg F and 28 =/-5 psi at 100 deg F.if you can rig up fittings to measure it.
But if you tap a bit and measure the inward change of the rod little by little, you'll likely solve the problem.
If you need more info, you can contact me directly by e-mail at <mrjschwell@comcast.net>. I can scan in and send factory info that way also if you wish.
