Opti-Spark 1996 Impala 5.7
Vehicle had the first 2 codes. P0133 oxygen sensor and P0372 primary High Resolution error. We replaced the Distributor with a aftermarket, coil and module. The distributor was not available in GM or Delco.
A New code P0336 has replaced the code P0372. (oxygen code will return after time). Symptoms are similar: runs fine cold but the hotter it gets the more likely it may stall and have a hard start like the timing is too advanced. (has broken 2 starters)
Replaced the opti-spark distributor behind the balancer and water pump. It does not have the shaft like the older optis but has a notch when installing that can only go one way. We replaced the timing chain kit and 2 more distributors of different brands, the last being ACCEL.
The Lo Resolution is off +20 degrees on the scanner pid. If you count the high revolution waves (360) between the start counting at the falling edge of the crank sensor to the beginning of the Lo Resolution sensor I have 20 waves. Same as the scanner pid shows.
So …. since it has a running problem like timing too high (because of hard start like advanced timing ), distributor cannot be adjusted, no slack in new chain kit, Tested all 3 signals at the PCM cranking and running, nice square waves, (see photo).
Could 3 different brands be machined wrong? Could PCM do this?
Possible spun crank trigger? I will look further in my older info. Was cylinder #1 at TDC on compression stroke when distributor replaced or just the slot used as reference? Beware of Aftermarket/ Dorman balancers, the triggers can be out of location on them.
Hello-ebay gm part #… Gm is selling them again. Reman, with the good mitsubishi optical pickup installed. 96 will run with the crank sensor disconnected. It is only there for misfire diagnostics in 1996 for the pcm.
Thanks Frank. That one part #… has a spline in the camshaft, mine only fits one way. Mine looks like this one attached.
If you have an actual 96. my number provided will fit. I know. I needed a new opti for my 96 z28. Re pinned the harness connector from my 96 dist and it worked fine. Do you have 2 vacuum lines attached to your dist?
Optional spark as I refer to them, whomever decided it was a good idea to put an 8 volt optical sensor in the same proximity as the 20,000 volt secondary voltage should be fired. This was GM's red headed step child from day one. If this is something the customer wants to keep, Torqhead LTD makes a 8 coil plug and play conversion that eliminates the optispark completely and updates the ECU to the…
+1 on the torqhead. I have installed over a dozen of those on F and Y bodies and they work great. Even the best optisparks start to break up at high rpms, the torqhead is good as fast as you can spin it.
William >>whomever decided it was a good idea to put an 8 volt optical sensor in the same proximity as the 20,000 volt… did their homework and it worked just fine in that configuration for the application. Problems were mostly due to coolant intrusion (water pump leak) and internal binding. A typical ignition scope diagnosis would include WOT (fuel cut) cranking to watch for secondary…
Make sure the crank wheel is not flipped around. I once had one that came in with a similar issue and when they installed the new timing chain and gears, put the crank wheel on the snout backwards. Also, if not a Delco opti, MSD is the only brand I have had decent luck with (75% of them work well) after dynaspark stopped making them. You can check it by pulling out the ckp. If the wheel is more…
I know this might be off topic but do you mind sending me a few pictures of the maf of this Impala and the connector location on the wiring harness? I’m doing a Impala 5.7 and putting a roller engine in and can’t find the right maf and can’t find the connector on the harness.
What about the Module under the Coil bracket? Was it changed the first time? And a second time? Or the old original one put back on & tried ? It seems to me with new different codes it is one of the parts that was replaced. Were the 2 broken starters replaced after the the first opti replacement? or after the timing chain job?
To answer your question of 3 different brands of distributors being machined wrong is yes!! I went through that a couple of times with aftermarket GM distributors.You need to compare with the original by lining up each distributor rotor where #1 cylinder would be,there is a notch or line on the housing,and see if the gear is in the same exact position. I went through a few…
One other thing, Where does the crankshaft sensor get it's location from? The reason I'm asking is if it is off the flywheel you might have a cracked flywheel. Just a thought.
I finally got back to checking a little more into this, Check the knock sensor wiring for shorting. Also this should be a 5V ref signal system. If it is showing 8V, suspect a bad block or harness ground. Start at the battery and clean every ground well and retighten.