bobd_1999

When below 10 degrees outside car cranks but won't start- Once warms up starts right away - When cold cranks, sometimes tries but deseils or backfires. Checked codes and get 12,51,21,55. Does a air temp sensor. coolant temp sensor, or throttle position sensor send codes when bad ? Has anyone had this problem? Any replies are appreciated!

tempfixit

In case you don't have a list of code definitions here is a link:

http://www.allpar.com/fix/80s-codes.html

Which engine and mileage on vehicle?

Do you have to floor the accelerator to get to start?

Have you checked the fuel pressure with a fuel pressure tester?

When cold starting have you turned the ignition switch to run for 5 seconds turned off and then attempted to start to see if that helped?

Try spraying carb cleaner at cold start to see if it starts like it suppose too?

I had similiar problem with a 3.3 in a voyager van and it was a faulty fuel pressure regulator on the fuel rail.

Normally these sensors will throw a code.

Don't worry about codes 12 and 55. 12= disconnected battery in last 40 start cycles. 55 is end of codes.

51 and 21 both refer to the 02 sensors but should not have any affect on start up since they should be in open loop mode. Have you seen a change in MPG?

Here is a link for testing fuel pressure:

http://www.autozone.com/shopping/rep...00c1528006ac19

Go to autozone.com and click on repair info this is a online manual for your car.

Hope this helps