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Fiero Troubleshooting Guide


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Go to the bottom of the page to view the trouble code section. Each section includes likely causes for the problem listed.

Engine: - Engine lopes while idling or idle is erratic
1 - Vacuum leak
2 - EGR valve leaking or plugged PCV valve
3 - Fuel pump not able to maintain required fuel pressure
4 - Leaking head gasket
6 - Timing chain and/or gears worn
7 - Spark plugs worn or not gapped correctly
8 - Ignition timing not correct
9 - Air filter clogged

Engine starts but stops immediately
1 - Loose or faulty electrical connections at the distributor, coil or alternator
2 - Insufficient fuel reaching injectors
3 - Vacuum leak (check at gasket between intake manifold and throttle body)

Engine difficult to start when cold
1 - Battery not charged or low
2 - Fuel system faulty
3 - Fuel system leaking
4 - Distributor system faulty

Engine difficult to start when warm
1 - Fuel system faulty
2 - Corroded battery connections
3 - Clogged air filter

Engine stumbles on acceleration or misses throughout driving range
1 - Spark plugs faulty
2 - Fuel injection system faulty or needs adjustment
3 - Fuel filter clogged
4 - Incorrect ignition timing or faulty ignition system
5 - Faulty emission system
6 - Vacuum leak in intake system or vacuum hoses
7 - Cylinder compression low

Knocking or pinging sound during acceleration
1 - Incorrect octane fuel used
2 - Ignition timing incorrect
3 - Damaged spark plug wires
4 - Worn or damaged distributor components

Loud knocking or ticking that matches engine rpm
1 - Rod bearing out of tolerance
2 - Broken or damaged rocker arm
3 - Damaged cam

Overheating
1 - Insufficient coolant in system
2 - Water pump drive belt defective or water pump faulty
3 - Faulty thermostat
4 - Radiator cap not maintaining proper pressure
5 - Ignition timing not correct
6 - Obstruction clogging cooling system
7 - Coolant fan motor or relay faulty

Clutch: - Clutch starts to engage even when pedal is pressed to the floor
1 - Faulty master or slave cylinder
2 - Broken or damaged clutch components

Clutch pedal firmly stops before reaching floor and/or clutch won't release
1 - Clutch release arm broken or damaged

Pedal feels spongy
1 - Air in system

Unable to select gears when pedal is pressed
1 - Faulty clutch disc and/or pressure plate
2 - Fork and bearing not assembled properly
3 - Faulty transmission

Clutch slips
1 - Clutch plate worn
2 - Clutch is new and requires normal use to seat the plate properly
3 - Weak diaphragm spring
4 - Rear main seal leaking spilling oil on the clutch plate

Squealing sound from engine compartment when clutch is slipped
1 - Worn clutch components

General: - Excessive fuel consumption
1 - Clogged air filter
2 - Oxygen sensor faulty
3 - Incorrect ignition timing
4 - Fuel injection system damaged or worn

Clicking noise during cornering
1 - Worn or damaged outboard CV joint

Knocking or clicking noise from engine compartment at low speeds, matches vehicle speed rather than engine rpm
1 - Worn axle CV joints
2 - Worn side gear hub centerbore

Clunk sound on acceleration or deceleration
1 - Loose, worn or damaged engine mounts

Noise when transmission is in neutral and engine running with clutch released
1 - Damaged input gear bearing
2 - Damaged clutch release bearing

Difficult or almost impossible to shift transmission into gear, especially first gear or reverse with clutch pedal pressed to the floor
1 - Clutch not releasing or faulty clutch (see clutch symptoms)
2 - Transmission cables out of adjustment
3 - Faulty transmission

Air appears in cooling system even after being filled correctly. Results in overheating and problem repeats of cooling system is refilled.
1 - Broken or cracked impeller disc on water pump
2 - Water pump loose

Quiet hissing sound coupled with fuel smell from engine compartment
1 - Main fuel inlet line at fuel rail not installed properly or loose

Tires produce smoke when engine is set at 4000 rpm and clutch is released
1 - You own a V-6 Fiero and can't resist
2 - OOPS!!!
3 - You're getting ready to change your tires
4 - You're winning a bet
5 - Just testing
Trouble Code Diagnosis If the check engine light comes on, you can identify the cause by connecting the bottom-left side terminals with a paper clip. Turn your car off, insert clip into terminals, connecting them electrically. Turn the ignition on, but do not start the car. Count the number of blinks the check engine light displays. The first series of blinks gives you the first digit of the code, the second series is the second digit (imagine that). Code 12 (one blink, followed by two) will blink twice and then any stored codes will follow. Below is a diagram showing which terminals to connect. The diagram is based on the terminal facing away from the firewall, observed from the front.

---------------
|= = = = = = =|
|+ + = = = = =|
---------------
Code list:
12     No reference (initial signal)
13     Oxygen sensor circuit (possible TPS problem, check wiring to O2     sensor, O2 sensor faulty)
14     Coolant sensor circuit (check wiring to coolant sensor, replace         coolant sensor)
15    Coolant sensor circuit (same as above, check wiring to ECM)
21     Throttle Position Sensor (check wiring from ECM to TPS, check     TPS, replace     TPS)
22     Throttle Position Sensor (same as above)
23     Manifold air temperature (check MAT sensor, check wiring, replace     MAT)
24     Speed sensor (faulty speed sensor, check TPS setting, check         connections at ECM)
25     Manifold air temperature (check voltage from MAT to ECM, should     be above 4 volts, replace MAT sensor)
32     EGR system (check EGR system, replace EGR valve)
33     MAP sensor (check vacuum lines from MAP sensor, check         connections at ECM, replace MAP sensor)
34     MAP sensor (voltage is likely low from MAP, replace MAP sensor)
35     Idle air control (closed idle speed out of tolerance, replace IAC)
42     Spark timing (consult repair manual, replace HEI modual)
44     Lean exhaust (check for vacuum leaks on hoses, at TBI gasket or     intake manifold gasket, replace O2 sensor)
45     Rich exhaust (check fuel vapor canister for presence of fuel, replace     O2 sensor)
51     PROM (check for proper installation of PROM, replace PROM)
52     Fuel CALPAK (check for proper installation of CALPAK PROM ,     replace PROM)
53     Voltage high (check charging system)
55     ECM (check ECM ground connections, replace ECM)

This information is to be used to help you in discovering an answer to a problem with your Fiero.

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