Seeing some peculiar behavior with my 1996 Acura TL 3.2 with 80,000 miles.
Everything works fantastic on it, it is in great shape. Really nice car.
All of a sudden I'm getting something I have not gotten before.
I get in the car when engine cold and probably 65 degrees F outside, and the engine will revv up and go into its cold start routine of sorts, keeping RPMs up fairly high say 1500 or so, and at some point - sometimes right away, sometimes when engine warms up, sometimes for no reason at all with RPMs at 1000 or so, the engine will act like it's going to die, then revv up to 1500 or so again for about 1/2 a second, then repeat. RPMs go high/low/high/low/high/low and I've never seen how long it will actually do that. I typically shut off the car, and start back up.
Dealership said rear main seal is starting to drip, but they did a full inspection otherwise and says it checks out. This problem did not replicate when at the dealership.
I had dealership drive it for 100 miles themselves - loaned it to the mechanic for two weeks just to use and he never had an issue. Son drove 1000 miles and never had an issue. Wife driven and had it happen. Son has had it happen before as well. I thought they were both nuts when they described the situation, then today, at 6 AM running out the door, happened to me. Now I am sad.

Anyone have advice here?

 

From chatgpt:A 1996 Acura engine that is almost dying and revving high in a cycle could be caused by several issues. Some potential causes for this kind of behavior include:

1. Idle Air Control (IAC) Valve Problems: The IAC valve controls the engine's idle speed. If it's dirty, faulty, or stuck, it can cause erratic idle behavior, making the engine idle too high or almost stall.
   
2. Vacuum Leaks: A vacuum leak can disrupt the air-fuel ratio, causing erratic idle and engine surging. Check all vacuum lines and hoses for cracks, damage, or loose connections.
   
3. Throttle Body Issues: If the throttle body is dirty or malfunctioning, it can affect the airflow into the engine, leading to inconsistent idling behavior.
   
4. Mass Air Flow (MAF) Sensor: A dirty or malfunctioning MAF sensor can send incorrect airflow data to the engine control unit (ECU), causing erratic idling and poor engine performance.
   
5. Faulty or Dirty Fuel Injectors: If the fuel injectors are clogged or malfunctioning, they may not deliver the correct amount of fuel to the engine, causing idle problems.
   
6. Bad or Dirty Throttle Position Sensor (TPS): If the TPS isn't reading throttle input correctly, the engine may struggle to idle properly or fluctuate between high revs and stalling.
   
7. Ignition System Problems: Issues such as worn spark plugs, faulty ignition coils, or bad wires could cause misfiring, leading to the engine stalling and revving.
   
8. Engine Control Module (ECM) Issues: If the ECM is malfunctioning or has faulty sensors reading from it, it can result in erratic behavior from the engine.
   
9. Fuel Pressure Regulator: If the fuel pressure regulator is malfunctioning, it may cause inconsistent fuel delivery to the engine, resulting in a fluctuating idle.
   
10. Air-Fuel Mixture Problems: A poor air-fuel mixture (either too rich or too lean) can cause the engine to surge and stall as the computer tries to compensate.
    

If you’re not sure which one is the issue, a diagnostic scan with an OBD-II reader would be a good place to start, as it can pinpoint trouble codes related to sensors or system malfunctions.

 

Reset the idle. Unplug the battery for a few minutes. Then start the engine, make sure that there are no loads (A/C, defroster, radio, etc) and rev to 3000rpm until the 2nd time the fans come on. Then let the engine idle for 5 minutes without touching the gas pedal. Shut her off and then turn her on again to see if the idle is correct. If this doesn't work, see the thread on adjusting the cold idle air valve in the 1G RL section and then do this procedure.

 

I had that issue in the early 90's and it turned out to be a clogged fuel filter. Only mentioning it because it is one of the possibilities not mentioned by chatgpt.

In my case we let the fuel run too clise to empty and the sludge in the bottom of the fuel tank was sucked in and clogged the filter.

 

Behavior seems odd