SAAB Project Update: Digital Detective Work

detective-tools

Now that the Starlet is sold, we need to turn our attention back to the SAAB. If you have been following our project updates then you know that we have been trying to track down a few gremlins. Fuel injection and emissions systems consist of a series of electronic sensors and valves, so we just assumed that the rough idle and stalling was attributed to an issue there. Well, after taking some advice from our readers, we pulled out my trusty multimeter and a shop manual and started doing some detective work. We think you will be surprised by what we found.

mass-airflow-sensor

Whenever you search the SAAB forums for rough idle or stalling on these classic 900s, most responses include the acronym MAF. If you don’t know already, MAF stands for Mass AirFlow sensor. We were so convinced that it was the cause of all our woes that we pulled it out and cleaned the wire element inside and even considered ordering a rebuilt one. The cheapest we were able to find was $175 though and it was no guarantee. SAAB expert, Chip Lamb, chimed in on our last post and suggested that we test the resistance between pins 3 and 6 on our MAF. That may sound techie to some of us, but it is actually very simple. Go get yourself a good multimeter and set it to ohms. Then stick the red and black probes on the corresponding pins on the side of the MAF. We did it and were confident that the number would be way out of range. Well, imagine our surprise when the screen displayed a 398. We were shooting for 380 so this was a little off, but not enough to cause the kind of problems were were having. The search continued.

air-idle-control

Next we moved to the next most common blame on the forums. The IAC or Idle Air Control valve ($125). These can get gummed up and cause a host of problems so we were sure this was going to be the weak link! Again we referenced Chip’s comment. We were looking for 20 ohms between pins 1-2 and 2-3 and 40 ohms between 1-3. Ours was 21.1 on the first reading which is within the recommended +/-2 ohm range. The seconding reading was 43.7 which seemed a little high, but we still didn’t feel satisfied that we had found the problem. Then we started thinking about another comment made by one of our readers. Dave mentioned that coils can act funny when they get hot. Well, it did seem that the engine was running progressively worse as the temperature increased outside. The car was barely operable on hot days actually, so we decided to take a look at that coil before continuing our inspection of the sensors.

coil-culprit

The first clue that something was wrong, was the oil in the rubber boot that covers the end of the coil. Then the wire basically fell out of the end of the coil because it was so slippery from the stuff. Turns out that these coils are filled with oil to help keep them cool. Could this be our culprit? We wend ahead and hooked up our multimeter and took a reading on terminal 1 and 15. It was 1.8 ohms, but was supposed to be between 0.5 and 0.9. Hmm… Next we tested between terminal 1 and the center tower – 10,810. Bingo! We were looking for 7,200 to 8,200. We were way out of range, but the reading only proved what we already knew from the oil leak. Off it came and on went a shiny new Bosch coil ($60).

new-coil

After connecting everything back up, we gave the key a turn. Could it be this easy? Well, after a full day of driving the SAAB around doing errands, I am happy to say that the coil was our culprit. There are still a few bugs to work out to get things running in tip top shape, but the fact that I can make it further than the edge of our neighborhood is a good sign. So, for any of you with a fuel injected car, I definitely recommend a workshop manual and a multimeter. Just think of all the money we could have wasted by throwing parts at this car instead of locating the actual problem! Thanks guys for all the help.

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Comments

  1. Joe Howell

    Well done. A little detective work with the multi meter can save you a lot of time and money if you’re not afraid of tackling electrical work.

  2. stanley stalvey

    Throwing parts blindly at a car is a miserable, hateful waste of resources. Good job, gentlemen. Nice work..

  3. shawn

    When doing this kind of troubleshooting, start with the least expensive parts first… That way, if ya gotta guess, you are guessing cheaper to higher… Rather than higher to lower… Like wires n connectors first, capacitor n points n rotor, then coil etc.

  4. scot

    ~ Good write up. And educational, too.

  5. Andy

    aha! the difference between a technician who changes parts until the problem goes away and a mechanic who tests and tests and tests in a scientific manner until the problem is found. then fixes the problem.

    well done example of thinking while wrenching.

  6. Martin

    Nice job Jesse! Keep up the great work. Nice job on the Starlet too.

  7. thefatkid

    Great article. Reminds me of Zen and the art of Motorcycle Maintenance. First Check to see if you have fuel, move on from there.

  8. jim s

    that problem could happen on any car with a coil so it is/was not just a saab problem. good work finding the issue. have fun driving the car. looking forward to more updates.

  9. Bryan Cohn

    Always start with the simple, most basic things. Fuel, as in is there some in the tank? Is it getting to the engine? It is? Yea! :) Then its the spark check. If it knocks you on your ass when cranking while holding a plug wire (not the recommended process but who here hasn’t done it at least once, even if by mistake?) you got sparky sparky.

    I did, in my younger years working on cars solve a no start on a customers BMW by adding fuel to the tank. We charged the nice lady for a tank of fuel and thanked her for her business. We did give her a nice, quick lesson on how to read the fuel gauge. Her husband normally cared of such things……

  10. Richard V

    Been there with more than one customer car over the years of my shop ownership (British Car Service, Glendale and Eureka, CA). The customers were always so embarrassed but hey, worse things could have happened, such as a major repair instead of a tank of gas!

  11. john S

    Go the SLAB! Well done. Dont recall ever having a coil problem in our 99 thank God.

  12. paul

    Just got back from a trip & read this , nice, now do we like driving a Saab?

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