jb4xx

Last Saturday I bought a low mile (56k) black 93 trans am. Drove 150 miles to check it out, Test drove went fine, bought the car. Po had a recept for opti, wires, plugs from little less then a year ago.

Wife drove car 50+ miles to a town to visit relatives. We got to hotel and she took car for wash, best one she could including undercarriage. Drove back to hotel and out for brunch Sunday. After eating car just turned over, no fire. After checking all fuses, fuel pump relay and parking lot check for fuel pressure, 45 minutes passed, we were about to tow and car fired up. Drove horrible, tried to die at stop lights unless given gas, then cleared up. Po said it had "old gas" so I put some seafoam in with fresh gas. Tires were drycracked bad, didn't see that when checked car out so I bought tires, car started and stopped several times, no problems. Went to start car for 160 miles drive home, car started, as we talked in parking lot, car quit and would not start. No fire at plugs or coil.
After an hour, car started, drove 3-4 miles and quit, now on the highway. Car did same thing until I finally made it to truck stop before it died. Left it there and drove family home. Got trailer and drove 7 hours to get the car.

Car cuts off after running 3-8 minutes original icm would heat up so fast it would burn you, put it in frz, cool it down, car would start and run again for few minutes

Icm tested bad by a guy at o Reilly who didn't look like he knew what he was doing. AutoZone said they didn't have directions how to hook up icm to testers. Bought new icm and car still quits.
Bought new coil, car still quits

Tried running car with temp sensor on water pump unplugged, still dies.

Tested, system power is at icm when warm and cool.

Ecm going to opti harness shows 4.72 volts in a and b and 12 in c with key on car cold, same when warm

Fuel pressure stays at 40 constant, did not change when car died.

After car dies, sometimes starts and runs poorly for seconds, other times just turns over, no fire at all until cools/ sits for 30-90 minutes.

Help! Did I kill the cat by running poor icm or ruin opti eye in car wash? Don't want to keep throwing parts at it and this forum seems so helpful with diagnostic help.

Thanks for reading this far.

Code 16 has been read using clip method

Injuneer

DTC 16 indicates the ECM could not find the low resolution pulse signal from the optical cam position sensor in the Opti. When that code sets the ECM shuts down the fuel system. That code does not turn on the SES light.

Check both ends of the short Opti harness for corrosion or pin damage.

Clear the code and see how fast it comes back. Pull ECM BAT fuse for 30 seconds.

GaryDoug

First do what Fred suggests.

If you want to roughly check the Opti low-res pulse output, measure pin A as you did before and watch the meter while cranking (not running). If the meter reading fluctuates downward from the usual 4.5-5.2 volts, the sensor is working at least somewhat. If it does not, the cable connection at the Opti is suspect as well as the Opti itself. The 4.7 volts you are seeing is coming from the PCM, so it's making good connection to that end. The voltage you saw at pin C is normal.

jb4xx

Pulled the opti out and there was significant build up on rotor button inside the cap. There is no way this opti was changed unless it was replaced by one from junkyard. The rubber seal was old and yellowed. The wires looked old as well but checked out good with dark driveway test when running. I think the po was ripped off if he did actually pay for the invoice given to me. I would be wasting my time going after anyone for the parts I replaced.

I put new opti in, new coil, icm, coolant sensor, belt and car is not stalling anymore. Isles 15 minutes easy. Now I just need to build back confidence that it won't die and leave me stranded!!

jb4xx

Car is running good, replaced both temp sensors. Guage now works but shows temp gets up to 230 or so. I bled the system a couple times until just coolant came out. Fans don't come on unless you turn ac on. Fans came on before with old sensors but guage did not work.

Injuneer

Here's a way to check the temp sensors/circuits.

4th Gen LT1 F-body Tech Articles


The first fan should come on at 226*F and the second one at 235*F. Check the ECM for codes - a failed fan relay circuit will set codes. If it's "about 230" it may not actually be reaching 226*F.