20 Most Recent 1991 Chevrolet Lumina Questions & Answers

Trouble Code 42 indicates that there may be a malfunction in the Electronic Spark Timing (EST) system. During cranking, the timing is controlled by the ignition module and the ECM grounds the EST line. It expects to see no activity on this line at this time. When the ECM enters EST mode, it applies +5 volts to the BYPASS line and expects to see voltage variations on the EST line.
Reasons for the ECM to set Code 42:
1. System in BYPASS mode (i.e. EST line supposedly grounded) but activity sensed on EST line
2. System in EST mode (i.e. BYPASS line driven with +5 volts) but no activity seen on the EST line

Possible causes include:
1. BYPASS line is open or grounded
2. EST line is open or grounded
3. Poor connections between ignition module and ECM
4. Poor routing of EST harness and/or poor quality ignition wires (EMI induced electrical noise
5. Faulty or incorrect ignition module
6. Faulty ECM
7. Faulty Pick Up Coil
8. Faulty Ignition Control Module
9. Faulty Crank Sensor or the Crank Sensor magnet probe could be cracked

If cleaning the injectors got it running and not it won't start I'd look at something contaminating the injectors, try recleaning again and see if it starts, if it does clean the fuel system

check the o2 sensor wiring its grounding out or something is.

Had fule pump and filter replaced, 3 months later, same problem, car will not start, replaced Relay Switch, still wont work. any suggestions?

Clean the throttle body and maf sensors.

You can have a leak if is small put can stop leak if this not works you have a large leak.

On electronic fuel injection pumping an pumping an pumping the gas pedal does nothing without the engine running ! Pushing the gas pedal to the floor will cause the PCM - engine computer to go into clear flood mode . You have some very interesting ideas here , but not really how it works or is ! The vehicle will go into closed loop fuel control when the engine coolant temp reaches a definded temp an the O2 sensor get hot. She would run for a couple minutes and die which is open loop when running, closed loop is when the sensors kick and it would die. Pulled spark plugs, they were black meaning no spark. Can only be 2 Black spark plugs indecate a rich condition , over fueled , wet spark plugs indecate no spark .

Either you have bad weather stripping in one of the doors, or a bad heater core. Check all the stripping around the doors, and windshield. Does the car have heat?

Have you changed the battery

Cranksensor or ignition module !

Check for a stuck open EGR valve,it will have to be removed to be checked.Or you have a large vacuum leak,either one will increase idle and fuel causing hot cat and high idle.

it's and old car , ever give it a full tune up? the parts and steps listed under the 60,000 mile column?

Maybe a problem with instrument cluster? Usually the circuit works off resistance to ground. The sending unit in gas tank provides resistance to ground. The signal wire for fuel gage is a purple wire, if goes to fuel pump wiring connector. With key on, use digital multimeter, check for voltage. If no voltage, either problem with wiring circuit or instrument cluster. W/0 looking at instrument cluster, I don't know if you can replace gage itself w/o replacing instrument cluster? If voltage on the purple wire, ground it, while a helper watches the gage, if the gage starts reacting, then check the grounds for fuel pump wiring connector, if that checks ok, suspect the fuel pump sending unit has a problem.

Rerplace the speedometer cable as well as the speedometer,if it still does not work,chck the fuses!

Cant be sure but if its 91 its probably mechanical.check for cable going gearbox not wire cable probably inside cable broken or drive in gearbox

I may need your vin? Look on the backside of engine block, down low. May have to get under vehicle. Two wire connector, purple and yellow. If not there, check down by crankshaft pulley.

you will have to check for spark and fuel to see what is missing. then check for codes just in case there is one. then you will know what you have to check to find the problem.

bet on the fuel pump and old filter