Coolant Temperature Sensor, Crankshaft position sensor, or software?

[100%Saab]

I still have not solved my warm start stall problem with the Maptun stage 1 tune. The throttle body and fuel injectors have been cleaned and no air leaks have been identified. I need an expert opinion. Do I now start replacing parts? My 9-3 has no fault codes and otherwise runs fine. I have no cold start problems. I have an email in to Maptun with no answer yet. The updated Saab software untuned does not have the warm restart problem. I have read that the Coolant Temperature Sensor and Crankshaft position sensor can cause warm restart problems.

Options are: Be happy, live with what I've got and 210 horsepower. Cheapest option.
Replace Coolant Temperature Sensor, Crankshaft Sensor, or both. Inexpensive parts.
Buy the BSR stage 1 tune. Not a cheap option.
Or, something else like this is really the intake valves.

[Digger]

I don't know anything about Maptun, if the gage is working properly I doubt you will change anything by changing the temp sensor, but the car is going on 10 years old and the CPS doesn't last forever. Even if it's not the cause of the problem now, it's only a matter of time before it will be.

Replacing the CPS and sucking some seafoam through the intake to clean out the carbon are justifiable expenses and good preventative maintenance. Happy with the warm starting problem now only gives you time to time to take care of this before Texas goes from winter comfortable to July hot.

[100%Saab]

Thank you, Digger. My Saab Service Center in Florida, Swede Central, did not recommend replacing any parts. The CPS may need to be replaced in the future but not now. I have tried Seafoam in the past, but have already purchased a new can of Seafoam and will use it again. Maptun has responded. I am discussing the Lubbock altitude at 3,000 feet above sea level and if the software identifies a warm restart as a cold start in my 9-3. Will update if the issue resolves.

[avid0g]

Saab uses a single coolant sensor. The engine computer uses it to drive the temperature gage, and also to adjust when to use Cold/Rich and Warm/Stoichiometric. If the dashboard temperature always looks reasonable, then the sensor is also OK.

Normally, cold combustion runs slightly rich and warm combustion varies around 14.7:1, optimized using the oxygen sensors. If you only get stalling when warm, then probably the default warm tables are too lean or the program strays too far lean.

If you are always stalling when warm, start by monitoring the O2 sensors. These 4-wire sensors require about 30-60 seconds to heat themselves up. This begins as soon as you turn the key to Run. Once the engine computer sees valid output, it stops using the lookup table and begins trying to cycle around optimum air/fuel ratio. Therefore, if the engine runs well for only 30-60 seconds, then the lookup table is adequate and the O2 hardware and/or software is suspect. If you preheat the O2 sensors for a minute in the Run position before starting, you can influence how soon the software switches over; stalling much sooner.

There should be two catalytic converters, one between the sensors and one downstream of both.

The upstream sensor should consistently fluctuate above and below ideal. The downstream sensor should not fluctuate as much in amplitude.

This fluctuation is required for best operation of the Cats. If for example, the downstream sensor always stayed in the middle, then the downstream Cat would not work as well.

During spin-up the stock tuning runs slightly rich. Of course, performance tuning may depart from Stoichiometric, and run much more rich (and more often).

Running rich may overheat the Cats and/or contaminate the O2 sensors with soot. Sadly, some performance addicts will drill out their Cats and isolate the O2 sensors (intentionally causing reaction-lag).

[100%Saab]

For both the original Saab software and Maptun stage 1 after sitting for approximately 20 to 40 minutes, my 2008 9-3 2.0T will start fine but then stall almost immediately. If I start it at say 17 minutes or 43 minutes and it starts, it will idle rough with low RPMs momentarily before starting. I start my 9-3 by turning the key with my foot on the brake. I can overcome the warm start stall by depressing the gas pedal when starting. This is what I do after 2 straight stalls. After the 9-3 fully starts it runs fine without any problems. The problem restarting the 9-3 is worse in hot weather but depends on how long the car has been driven.
The Saab updated software from 2009-2010 completely curses the problem. Even though Maptun has been telling me I have an air leak I can't see this as anything other than a software problem. However, if someone knows that a sensor or hardware problem could cause the Saab software to work and the Maptun software not to work I would be willing to change the part. Thank you.

[100%Saab]

BSR has responded to my inquiry. They expect the BSR stage 1 software to work with my 2008 9-3. They also have a 2 year warranty period for their software. I will probably wait until their next sale. So far, Maptun has not responded to my latest email.

[swisssaabist]

Cool you've find an alternative GL ...

[Digger]

For both the original Saab software and Maptun stage 1 after sitting for approximately 20 to 40 minutes, my 2008 9-3 2.0T will start fine but then stall almost immediately. If I start it at say 17 minutes or 43 minutes and it starts, it will idle rough with low RPMs momentarily before starting. I start my 9-3 by turning the key with my foot on the brake. I can overcome the warm start stall by depressing the gas pedal when starting.

My older 9-3 has a different throttle body than yours does and I haven't spent any effort looking into what the newer one will do, or what problems the software update resolved, but what you're describing here sounds like the electronic version of vapor lock. Have you ever tried forcing fuel air to default by unplugging the mas air sensor when the car won't warm start with the stage 1 tune?

[100%Saab]

Interesting idea. After doing some research on mass air sensors, I don't think I'll disconnect mine since it is unlikely to be a permanent fix. Without warning indicators going off and a prior Saab software fix, this is going to be an altitude (thin air) problem. The hot engine just makes the air thinner and pressing the gas pedal just supplies more air. Saab, Maptun, or BSR will have to explain how their software updates fix or cause the problem.

2008 Owners manual - Cars with automatic transmission:
1 The selector lever must be in the P or N
position.
2 Keep your foot on the brake pedal.
Note! Once the engine has started, the
brake pedal will sink. This is perfectly
normal.
3 Start the engine. Let the ignition switch
spring back as soon as the engine has
started and is running smoothly.
Allow the engine to idle for about
10 seconds.
I used to start cars in the 1960s by depressing the gas pedal, which will work if you are in park otherwise it can be dangerous. So, I will wait for a reply from Maptun. Thanks for the responses.

[Digger]

Not meant to be a fix, trouble isolation or temporary get you home on a rainy night only. Running with out MAS connected for any length of time will ruin catalytic converter.