My 1997 Pontiac Firebird Trans Am will not idle on its own.



Codes:

• P1361
• P0336 (listed as moderate severity on my scanner)

P0336 has been stored/pending since I bought the car in Oct 2024. At that time the car ran perfectly with no drivability issues.



Failure event:



In fall 2025, while driving on the highway, the car suddenly went into limp mode and I lost normal throttle and transmission control. I was able to coast into a parking lot, left the car overnight, and it started the next morning and drove home.



Since that drive home, it has not been able to idle.

Parts replaced (Dec 2025 – present):

• Battery
• Alternator
• Starter
• Optispark
• Opti harness
• CKP
• Ignition coil
• ICM
• Spark plugs
• Plug wires
• IAC
• TPS

Current symptoms:

• Hard starting (needs multiple cranking attempts)
• Will eventually start if the fuel pump is allowed to cycle/prime
• Will immediately stall if left to idle
• Runs and stays running only with throttle input
• Runs progressively better at higher RPM
• No backfires or popping
• Noticeably rich condition (fuel smell + darker exhaust)

 

Have you checked the fuel pressure? You need to check for rapid pressure leakdown after the pump primes and shuts off.

P1361 is pointing to the ICM circuit. Have you verified the connections on the ICM?

http://shbox.com/1/4th_gen_tech2.html#opti_test

P0336 for the crank position sensor should not cause any problems, the CKP sensor was only added in 1996/97 to meet the OBD-2 requirement for misfire detection. But when the code sets you can’t pull misfire codes and data from the PCM. Have you tried to pull misfire codes and counts? The requires a scanner with GM enhanced parameters.

And a “heads up”….. 100,000++ members and hardly anyone comes here any more. Maybe a half-dozen semi-active members, most of us LT1 enthusiasts. May take a while to get responses. I’m here every day for a few minutes, but the main activity is banning spammers.