History: 92 S10 4.3 CPI, obviously sat for a good long time somewhere before I bought it. Replaced dist. cap, wires, plugs, ignition coil. Repaired massive fuel leak under the plenum. Persistent Error code 43 (knock sensor).

Incident: While driving 30 miles to Yucca Valley from 29 Palms, engine began to sputter after a short pit stop halfway there and wouldn't go over 50. Labored, very hard. Not a steep climb at all, just 1200 feet over 30 miles. Tranny seemed hot, engine temp never exceeded 210.

Replaced ignition control module while in Yucca Valley (what the hell, the original was well, the original). On return trip, a great improvement although engine still ran rough at low RPM.

Stopped in Joshua Tree and finally found the burned wire end to the knock sensor, connector was TOAST. I stripped it back a bit and shoved the wire (a single blue lead) into the knock sensor. Error code 43 disappeared, but a new code 42 now shows up. I am certain the control module was installed correctly. The thing really acts for all the world like the gas has sediment in it, it's that kind of roughness. But the 42 keeps coming back after I clear it. No 43 any more. There was NO 42 before this incident.

Ideas? Could the timing procedure have been incorrectly applied, causing the EST system to be "slap happy"? Could it really be dirty gas? The filter is fine.

 

According to the Haynes manual, the EST module has 4 terminals, A-D:

a) Reference Ground Low. This wire is grounded in the distributor and insures that the ground circuit has no voltage drop which could affect performance. If it is open, it may cause poor performance.

b) Bypass. At about 400 rpm the ECM applies five volts to this circuit to switch spark timing control from the HEI module to the ECM. An open or grounded bypass circuit will set a Code 42 and the engine will run at base timing, plus a small amount of advance built into the HEI module.

c) Distributor Reference High. This provides the ECM with rpm and crankshaft position information.

d) EST. This circuit triggers the HEI module. The ECM doesn't know what the actual timing is, but it does know when it gets the reference signal. It advances or retards the spark from that point. If the base timing is set incorrectly, the entire spark curve will be incorrect.

OK, the circuits which have my attention, in this order, are b,a,d. No pun intended. The reason is, I notice that on a mellow take off, it takes a few seconds for the engine to speed up and get me going. Up to that point it sputters. There seems to be almost no correlation between this and how much gas I'm giving it (mellow take off, remember). It seems to be a function of time. This makes me feel that the Bypass circuit is not doing its 'thang'. The 'a' circuit is less specific, but still mentions "poor performance". 'd' is last on my list simply because testing this function is more complex and will require me to buy test equipment that I don't currently have. I'm hoping to isolate the problem before laying out the coin.

When it gets light out, I intend to go over these connections and make sure they are solid (man I hope they're not, that would solve the problem - lol). I'll be getting back here to report the results.

 

Any luck with this?