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Cav
Tech Tips
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I find Cavs rather easy to work
on, and have learned a few tricks. If you have a tip or trick to share,
please send them to me at this link: Tech
Tips
Z24
Digital Dash Woes
Low
Oil Pressure Indicator
Pulling
Trouble Codes
Direct
Ignition System Misfire
Alternator
Light "On"
'87-89
L4 Vacuum Diagram
'85-86
V6 Vacuum Diagram
Leaking
distributor or oil-pump drive
Z24 Digital
Dash Woes
Frustrated
that you can't even see how much gas you have if the digital cluster is
out? Well, you can check the resistance of the fuel gauge sending unit
with an ohmmeter. The fuel tank unit connector is at the back of the vehicle,
above the filler neck.
Graphic made with 
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Low Oil
Pressure Indicator
Does your oil pressure indicator come on at idle with the engine warm?
I had that problem for about a year. I pulled the pan off and replaced
the pump. I also checked the main and rod bearings. They were fine. Since
the engine made no harsh noises, I figured the problem was the oil pressure
sending unit for the gauge. So I replaced it, and voila! No more oil pressure
light. This sending unit is fairly large and is located in between the
oil filter and A/C compressor. It is very easy to change.
Graphic from ST366-86 Cavalier Service Manual
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Pulling
ECM Trouble Codes
You don't need any specialized equipment
to read trouble codes that are stored in the ECM if the "Check Engine"
(on some cars it says "Service Engine Soon") light comes on. All you have
to do is jumper terminals "A" and "B" and watch the light. It will flash
once, pause, then flash twice. This is code 12 and indicates that the system
is functioning normally. This will be repeated twice and then any codes
will be displayed in numerical order in the same manner.
Here are the most common codes:
12
13
14
15
21
22
23
24
25
33
34
42
44
45
51
52
53
54
55 |
System Check
Open Oxygen Sensor Circuit
Coolant Temp Sensor (Low voltage)
Coolant Temp Sensor (High voltage)
Throttle Position Sensor (High voltage)
Throttle Position Sensor (Low voltage)
Manifold Air Temp Sensor (Low voltage)
Vehicle Speed Sensor
Manifold Air Temp Sensor (High voltage)
MAP Sensor (High voltage)
MAP Sensor (Low voltage)
Electronic Spark Timing
Lean Exhaust Indication (Low voltage)
Rich Exhaust Indication (High voltage)
Faulty Mem-Cal
Fuel Cal-Pak Missing
System Overvoltage (check for alternator problem)
Fuel Pump Circuit
Faulty ECM |
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Direct
Ignition System Misfire
Does your DIS-equipped GenII L4 have a misfire from hell? If you've
checked the plugs and wires then it most likely is either the ignition
module or one of the coils. To find out, disconnect a plug wire with the
engine running. When you find the cylinder that is missing, shut the engine
off. Remove the module/coil pack from the engine. Swap the coils, but route
the plug wires as original (ignore the number markings on the coils). Reinstall
the coil pack and restart the engine. Remove the same plug wire as before.
If the misfire is on the same cylinder pair, then the problem is the module.
If the misfire changes to the other pair, then the coil for that pair is
bad.
Graphic made with
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Alternator
Light "On" ('87-later CS-series)
Is the "VOLTS" light on all the time and your battery going dead? A
very simple check will determine if the problem is your alternator (I've
had two go out on my '87 Cavalier 2.0L). Connect a voltmeter across the
battery with the engine running. Voltage should be around 14 1/2 volts
at idle. If it is lower than 12, the battery is not being charged. With
the engine still running, disconnect the plug at the alternator (NOT the
large "BAT" terminal!!) If the light goes out, the alternator is at fault.
If the light stays on, you have a short in the wiring.
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'87-89
L4 Vacuum Diagram
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'85-86
2.8L V6 Vacuum Diagram
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Leaking
distributor or oil-pump drive
On the V-6's the right lifter bore is also the main oiling
bore for the engine. This bore also feeds the
distributor. GM only puts a o-ring seal there. Install a new replacement
o-ring (the dark brown one - it is thicker) and distributor GASKET from
a small block chevy. It fits perfectly.
Thanks to Wayne Murphy for his tip
