Code 42 spark timing on a 86 s-10 blazer - Cars & Trucks

Refer to the link for an explanation of the fault code 42 GM Code 42 Electronic Spark Timing or Bypass Fault FreeAutoMechanic

It needs at least 60psi fuel pressue to start. You need to check fuel pressure with a gauge.
If the dist cap or rotor is bad, the spark will not be on the right plug at the right time. Same goes for a faulty distributor or a problem with the timing chain. And the ignition module.
Also check the ecm for trouble codes.

Try spark plugs and spark plug wires. Unless you just changed them. Possibly distributer cap and rotor if that doesn't fix it. To really fix it right you should probably pull all plug wires off one at a time and see which one is not firing. Then pull out the plug put the wire back on it and see if it is sparking while cranking it over. If you have spark, it could possibly be an injector problem. Please rate my answer.

Code 42 is "Ignition Spark Timing". Either the engine (Cam/Crank) timing is off, or there is a problem with the ignition wiring, the ignition module or the engine control module.

problem code 34 is in map sensor curcuit is to high. code 42 is electronic spark timing malfunction. for 42 replace est module in distributor, it has the est built into it. it controls the timing. code 34-- replacing map sensor should solve problem. good- luck!!

http://thirdgenchat.org/ecm_codes.html

Hi,there is label number on spark plug wires.try to match the same number and replace one spark plug wire and one spark plug at the time!!!
good luck!!!!!!

If the pressure is slow to rise, you should consider changing the fuel filter if it has not been done in the past 30,000 miles.
Next, disconnect a spark plug and check for spark while engine is cranking. Use a spark tester or old spark plug grounded to the engine block.
Let me know.
Regards,

Trouble Code 44 indicates that the O2 sensor is showing a persistently high exhaust oxygen content (lean), despite the efforts of the ECM to increase ...
Code 42 : Electronic spark timing (EST) circuit fault

Hey, your right about code 42 being the Electronic Spark Timing. The Electric Spark Timing Bypass curcuit or EST circuit is either grounded or open. A malfunctioning HEI module can cause this code so I suggest maybe trying to replace the HEI module. Good luck!