[Seatsabouttwenty]

New plugs, .035 gap, wires and cap 10k agonew egr, no vaccum leaks. New o2 sensor.
I adjusted timing to zero with the tan wire unplugged, then plugged it back in. Seems to run better when cold.

The car had a tiny hot rod air filter and I am removing that and going back to all stock for California emissions. So I am running the sensors in the air cleaner again

This connector is close to the distributor. What should it connect to. Looks like it comes off the coil.

 

[Seatsabouttwenty]

I am getting code 42, electronic spark timing circuit. How do you test this circuit?

 

[sven914]

The first thing you want to do is clear the existing codes by disconnecting the negative battery terminal. Code 42 can be set accidentally by cranking the engine for longer than 10 seconds or by cycling the ignition ON/OFF/ON in quick succession for 5 seconds; in either of these cases, there would be no electrical/mechanical reason for the fault.

After you have cleared the codes, start the engine normally (make sure you don't crank it for an extended period of time), and observe the condition of the Check Engine Light. The check engine light may not eliminate, so check the codes to see if 42 has been set again. If the code is not set, then the issue is intermittent or was caused by the aforementioned cranking conditions; to rule out any intermittent causes, make sure the ground and electrical connections to the Distributor HEI module are all tight and properly connected, and also verify that EST wiring harness is not near any of the plug wires, as this could cause RF interference in the circuit.

If the code is present immediately after restarting the engine, then the issue is either in the Distributor HEI module or the wiring harness that connects it to the ECM. The diagnostic information in my service manual is similar to your ignition system, but not exactly the same (mine being an Oldsmobile and yours being a Chevrolet) and I do not know where the differences are. If you wanted to repair an issue like this on your own, I would recommend getting a Factory Service Manual, which are usually available on eBay and were originally used by Cadillac dealerships.

Also, I believe that green plug is a test port, and is not supposed to be connected to anything.

 

[larryinalabama]

Might be as simple as the coil going bad, I had to put one on mine.

Reciently I had a hole in a vacumn line near the firewall behind the wireharness, it drove me crazy, but after about 3 hours I finally figured it out.

 

[Seatsabouttwenty]

After clearing codes and driving 80 miles no check engine light. Accelerated pretty hard through first and second gear after a short warm up 2 min. It's 70 deg f here in Cali.
Then when I got on the highway it feels like it's pinging.

I set the timing to zero, tdc, as per procedure. And I did have to change it, I advanced it. Thinking about retarding it so it runs right but afraid it will be out of spec for smog check.
Any thoughts or ideas would be priceless, thanks Jordan

 

[larryinalabama]

Other past problems Ive had are the vacumn line to the map sensor collapsing at the base of the throttle body. Throttle body gasket separated. Coolant temp. sensor connector corroded. You could also look at the injectors and see if they are spraying a "cone" pattern <look real close with a bright flash light>.

 

[brougham]

There's way with the buttons on the dash to clear codes without disconnecting battery.
Any number of things can cause hesitation. This is one of the things the service manual comes in handy for because it says what can cause it and how to check the various items.

 

[mjs182004]

Have you checked fuel pressure? I believe it should be around 13psi. At least it is for mine, but I have the 5.0L