Why does the check engine light of a 1986 firebird come on about 15 minutes after the car starts?

Answer 1

I own a shop, and do a huge amount of computer trouble shooting. Without getting technical, lets just say it comes on after the engine gets to operating temperature. This is because the computer doesn't take over the complete operation until it reaches 100 degrees. 15 minutes is a long time for a vehicle to come up to 100 degrees, so I would suspect you have a thermostat that is stuck open, or it is missing it completely. 100 degrees should be reached within 5 minutes or less. These are really bad to have temperature sensor issues. Go to Auto Zone, and they will pull the codes (for free) and even sell you the part you need to fix it with. I wouldn't ignore the light, it does mean something is out of parameter, and it causes the engine to use more fuel this way, so getting it fixed will pay for itself in no time @ $3.00+ a gallon.
Glad to help out, Good Luck!!!

Answer 2

You have a soft code setting and it is setting AFTER the car goes into closed loop. A quick explanation for closed loop is that when the engine reaches operating temperature, the computer takes on input from the various sensors in the engine. When it is first started, it is in open loop which is described best as on "autopilot" . the engine is basically running off of a preset number of values for fuel trim, timing, etc. Once it gets warm enough, the oxygen sensors, coolant temp sensor and many others are then sending signals to the ECM. the light is coming on because one or more of the emission related sensors is sending a signal that is out of range or a signal is absent. you'll need to pull the codes, which on that car you can actually use a paper clip at the ALDL connector under the dash and get a blink sequence to give you the codes. BUT, its best to have a mechanic scan it and diagnose the problem. A code isn't the answer. its just another diagnostic tool to isolate a problem. It's important to do this as some problems like a failing oxygen sensor can cause fuel control to be lost, the long term effect can be a failed catalytic converter from running to much fuel through the exhaust unburnt for example. It could be as simple as a coolant temp sensor failure too. Just have your mechanic diagnose it and get an estimate of repairs.

Answer 3

Begin by checking the oil levels. Usually it takes a car about fifteen minutes to make the oil reach optimum temperature, although it begins to heat up about three to five minutes after you start it. This is the most probable cause for your engine light come one, you're running low on oil.

Answer 4

Get the car scanned for codes.Probably 02 sensors not working properly not going into closed loop fast enough,or engine coolant temperature not sending correct signal.All temperature related.

Answer 5

You have a bad sensor. Pull the trouble codes and find out where the problem is.

Answer 6

Get the error code read at Autozone and see what's causing it. good luck.