91 PAU Starting Issue
sarotara
10-05-2006, 10:33 AM
Buick Park Avenue Ultra 1991 - 126k miles
When initially trying to start the car after it's been off for more than 60 minutes the engine just dies (about 80% of the time). Here is what happens:
1) Turn key in ignition
2) Engine cranks
3) Engine fires up and RPM jumps to about 1k-1.2k
4) Engine RPM all of the sudden drops down to 300-500.
5) Engine struggles for 1-2 seconds and then dies.
If the car fails to start up the first time, it always starts without any problems the second time. There is also a smell of gas from the exhaust if the engine failed to start the first time.
I have access to an EZ-SCAN AX6000 car scanner so if it helps I can post car data for the several seconds during a starting attempt.
The fuel filter on the car was changed several months ago, the spark plugs, the wires, and the coil were changed about a year ago. There are no trouble codes. Any ideas on what's going on would be appreciated. Thanks
When initially trying to start the car after it's been off for more than 60 minutes the engine just dies (about 80% of the time). Here is what happens:
1) Turn key in ignition
2) Engine cranks
3) Engine fires up and RPM jumps to about 1k-1.2k
4) Engine RPM all of the sudden drops down to 300-500.
5) Engine struggles for 1-2 seconds and then dies.
If the car fails to start up the first time, it always starts without any problems the second time. There is also a smell of gas from the exhaust if the engine failed to start the first time.
I have access to an EZ-SCAN AX6000 car scanner so if it helps I can post car data for the several seconds during a starting attempt.
The fuel filter on the car was changed several months ago, the spark plugs, the wires, and the coil were changed about a year ago. There are no trouble codes. Any ideas on what's going on would be appreciated. Thanks
wrightz28
10-05-2006, 10:41 AM
Definately scan for DTC's and post any hard/soft codes. that would be helpful.
Also check what the reported engine temp is and the ECm is showing a constant toggle from rich to lean or is it purely stuck to one side the mix.
2 possibilities off the bat are ICM or crankshaft position sensor[circuit].
Also check what the reported engine temp is and the ECm is showing a constant toggle from rich to lean or is it purely stuck to one side the mix.
2 possibilities off the bat are ICM or crankshaft position sensor[circuit].
sarotara
10-05-2006, 09:34 PM
There seems to be a constant switching between rich and lean flags, but I might be misinterpreting something so here is all the data:
Failed Start
http://ornus.org/images/failed_start.JPG
http://ornus.org/images/failed_start2.JPG
Successful Start
http://ornus.org/images/successful_start.JPG
http://ornus.org/images/successful_start2.JPG
In both cases, the engine is started at or near the "Trigger" point. Thanks for the help, it's really appreciated.
(Edit: By the way, I believe that in both of the above scans, the data was recorded from the computer once every second, but I'm not positive as to the exact frequency. I can change the frequency of data recording if needed.)
Failed Start
http://ornus.org/images/failed_start.JPG
http://ornus.org/images/failed_start2.JPG
Successful Start
http://ornus.org/images/successful_start.JPG
http://ornus.org/images/successful_start2.JPG
In both cases, the engine is started at or near the "Trigger" point. Thanks for the help, it's really appreciated.
(Edit: By the way, I believe that in both of the above scans, the data was recorded from the computer once every second, but I'm not positive as to the exact frequency. I can change the frequency of data recording if needed.)
HotZ28
10-06-2006, 09:41 AM
Looking at your failed start, that the battery voltage was only 11.6V then dropped to 9.4 at start-up and only recovered to 11.7V before shutdown. In addition, in an attempt to keep the car running on such low voltage, the PCM changed the air/fuel mixture to an extremely rich condition, before the engine shut down. The DIS ignition will not operate with battery voltage that low! :crying:
I noticed on the “good start” that the voltage was low before starting and returned to normal when the alternator kicked in! Check all your electrical connections at the battery and alternator. Also, have a load test performed on the battery. Your battery should measure 12.6V before attempting to start and go to 13.8+ after starting. Look at the normal start and you will see normal voltage.
I noticed on the “good start” that the voltage was low before starting and returned to normal when the alternator kicked in! Check all your electrical connections at the battery and alternator. Also, have a load test performed on the battery. Your battery should measure 12.6V before attempting to start and go to 13.8+ after starting. Look at the normal start and you will see normal voltage.
wrightz28
10-06-2006, 09:55 AM
Ditto with HotZ28
A battery with a static charge of 12.2V or less and a cranking voltage drop to less than 9.6V is not going to get the job done well if at all. Concurred also, check you connections and over all battery condition. Inspect the label for imanufactured date as well.
A battery with a static charge of 12.2V or less and a cranking voltage drop to less than 9.6V is not going to get the job done well if at all. Concurred also, check you connections and over all battery condition. Inspect the label for imanufactured date as well.
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