Replaced knock sensor, cleaned out radiator

Lesson for today: in a small-block chevy,


For fuck's sakes. I don't think there's any technical reason it should be connected to the coolant passage.  The wisdom at thirdgen.org suggests GM simply cheaped out and re-used an existing drain plug for the knock sensor.

GM's shop service manual, chapter 6E2-C5-1 - "Electronic Spark Control (ESC) System" does not mention anything about this. For the benefit of future generations, there should be a step 3.5 under Remove or Disconnect, namely "Prepare to swim in coolant". At least the stuff wasn't hot anymore.

Anyway, there's now a new knock sensor. Apart from some wiring harnesses, all ignition parts are new/replaced.

Since most of the coolant ended up on the driveway, I had an opportunity to flush the radiator, coolant reservoir etc as well. This actually came at a good time - there was a hideous amount of sludge in the system. Apparently I had messed up the coolant/water ratio last year as well -- the liquid had frozen during the winter and now coolant was seeping through the water pump gaskets. The pump will be cleaned and new gaskets installed, if I can manage to pull that thing out.


ESC module changed; Isolating the ignition problem

I've replaced the ESC module. Now almost the whole ignition system is new - except for the knock sensor and some wiring - yet the same problem persists. Here's a another home video showing the problem.

However, I've managed to narrow it down. If the EST bypass (aka set timing) connector is open, the engine runs just fine! The ECM sets error code 42 and the SES light comes on, as should happen when the connector is open.

So, the problem is somehow related to how the ECM controls spark timing.

Last time, I had set the spark advance to "apparently 0", like this:

In this position, when the bypass cable is disconnected, the engine sputters a bit and feels like it's hesitating on idle. So I rotated the distributor until the idle sounded smooth and stable - the timing is now on the last tooth:

            /           |
                 v v V V   O

I haven't seen _any_ of the tachometer flip-outs, stalling, sputtering etc when driving like this. The power - what little the stock TBI has - is mostly present too.


Battery negative cable, battery connectors replaced

Replaced the battery connector hacks with a pair of proper connectors that attach a Euro-style battery (terminals on top) to US-style wires. Cleaned up all the terminals & connectors.

Replaced the ground cable from the battery to the engine block.

Opened and re-tightened the TBI mounting bolts to correct torque (22 Nm).

The coolant fan switch cable is disconnected (and covered with tape), since I don't have the new connector yet. I tried grounding the wire (with the engine off, battery connected). As I understand this should have started the fan, but it didn't.


Nothing has changed. The car starts well when it's cold, but after 10-15 minutes, it starts to choke violently and the engine dies off. All coolant and engine temperature look normal in WinALDL.


8th spark plug replaced, knock ^H^H^H^H coolant fan switch connector damaged

I finally managed to lift the car up and replace the cursed #8 spark plug. Now all plugs are new AC Delco R45TS gapped at 0.89 - 0.99 mm. Of course #1 - #7 are half a year and a few 100 km older, but you can't have everything.

While I was working on this, I tried to inspect the knock sensor coolant fan switch connector that lives near the #8 plug. The plastic around the connector simply shattered into pieces before I could detach the wire. I was left with just the connector's metal pin hanging from the wire.

Update: apparently that wasn't the knock sensor, but the sensor that controls the coolant fan. The connectors are nearly identical though...

It's surprising how bristle that connector is, knowing it's subjected to temperatures between -30 and +100 or even more, water, grime, etc.

New connector, knock sensor and knock sensor module (ESC) are on their way. Due to the transport costs from the US to Europe, it's always cheaper to order more parts at once.


Battery terminals cleaned

Took apart the US-eur adapter in the positive battery terminal and cleaned it.

I also replaced the positive battery connectors in the junction block next to the battery that connects the battery, charger output, (???) fuse and a 4th wire with a fusible link.

Cleaned up some of the cables.

Cleaned and reattached the battery -> chassis ground cable.