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- X-Last-Updated: 2004/04/13
- Followup-To: poster
- From: faq@allpar.com (Dr. David Zatz)
- Newsgroups: rec.autos.makers.chrysler,rec.answers,news.answers
- Subject: rec.autos.makers.chrysler FAQ, Part 3/6
- Organization: http://www.allpar.com/
- Summary: Repairs and Troubleshooting
- Approved: news-answers-request@MIT.EDU
- Originator: faqserv@penguin-lust.MIT.EDU
- Date: 04 May 2004 12:58:56 GMT
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-
- Archive-name: autos/chrysler-faq/general/part3
- Posting-Frequency: 15 days
- Last-modified: 2004/4/13
- Version: 4.5
-
- Modifications and detailed fixes are at the web site -
- http://www.allpar.com/
-
- IMPORTANT. Do not attempt to respond to faq@allpar.com.
- Due to spam this address DOES NOT GO ANYWHERE.
- Instead, reply to faq2 at that allpar /dot/ com address.
- Thank you.
- - - - - - - - - - - - -
- See the very last part of this section for reading ESA computer codes
- without a scan tool! Useful for those without the key-turn-watch-light
- feature (e.g. 1985 Caravans) -- and those with it!
-
- Note that engine codes have been updated since this list was created. See
- http://www.allpar.com/fix/codes.html for an updated list.
-
- Contents:
- 1. Engine Codes
- 2. [Outdated and removed]
- 3. Classic Car Troubleshooting
- 4. Reading codes without a scan tool
- (computer controlled, carbureted engines)
- 5. Crankcase inlet air filter, 2.2/2.5 engines.
-
- DISCLAIMER:
- While effort has been taken to insure the accuracy of the information
- contained in this FAQ list compilation, the author and contributors
- assume no responsibility for errors or omissions, or for damages
- resulting from the use of the information. The information may be
- reproduced IF credit is given to the writers and the maintainer; and
- that it is not published without the prior written permission of the
- maintainer; that the maintainer receives, without needing to ask, a free
- copy of the final material; and that no changes are made without the
- express permission of the maintainer (David Zatz who is at
- http://www.allpar.com/).
- - - - - - - - - - - - -
- The latest copy may be obtained from http://www.allpar.com/faq.html
- - - - - - - - - - - - -
-
- FAQ for rec.autos.makers.Chrysler - Part III
-
- ********************************************************
- COMPUTER CODES
-
- THESE ONLY WORK IF YOU HAVE FUEL INJECTION. Otherwise, see the web site or
- the "troubleshooting electronic feedback carburetors" section.
-
- Start with the ignition off. Within five seconds, switch the key on, off,
- on, off, on. (On is *not* start!)
-
- The "check engine" light will flash. Count the flashes Each code is a two
- digit code, so a (for example) 23 would be FLASH FLASH <pause> FLASH FLASH
- FLASH <loong pause>
-
- It will never flash more than 9 times, watch for pauses!
- 55 is end of codes, 33 is normal if you don't have air conditioning.
-
- When the computer indicates major failure, it will activate Limp In mode,
- which guesses about data to compensate for sensor failure.
-
- *** NOTE - NEWER VEHICLES ***
-
- See http://www.ptcruizer.com/computer-codes.html for a new, revised list of
- computer codes and instructions on how to get them. These codes appear to
- have been phased in starting in around 1998.
-
- ***
-
- Please note that some codes are NOT included below, this is not a complete
- listing. (From Herb with additions by Charles Hobbs. Basis: Mopar Mailing
- List info.)
-
- * Activates Power Limited/Check Engine light.
-
- 11 No ignition reference signal detected during cranking (bad Hall
- effect)
- OR timing belt skipped one or more teeth;
- OR loss of either camshaft or crankshaft position sensor
- 12 Battery or computer recently disconnected
- - Fraser Shortt said code 12 appeared with some other codes
- in 1989 and possibly later computers as well.
- 13* MAP sensor or vacuum line may not be working
- 14* MAP sensor voltage below .16V or over 4.96V
-
- NOTE - on early Neons, a computer error may light the Check Engine light and
- show one or more of these codes. If this happens, bring it in so the dealer
- can
- reprogram the computer (about ten minutes).
-
- 15 No speed/distance sensor signal
- 16* Loss of battery voltage detected with engine running
- 17 (1985 turbo only): knock sensor circuit
- 17 Engine stays cool too long (bad thermostat or coolant sensor?)
-
- 21 Oxygen sensor signal doesn't change (stays at 4.3-4.5V)
- Probably bad oxygen sensor
- 22* Coolant sensor signal out of range
- - May have been disconnected to set timing
- 23* Incoming air temperature sensor may be bad
- 24* Throttle position sensor over 4.96V (SEE NOTE #3)
- 25 Automatic Idle Speed (AIS) motor driver circuit shorted
- or target idle not reached, vacuum leak found
- 26 Peak injector circuit voltage has not been reached
- (need to check computer signals, voltage reg, injectors)
- (SEE NOTE #4 BELOW)
- 27 Injector circuit isn't switching when it's told to (TBI)
- OR (MPI) injector circuit #1 not switching right
- OR (turbo) injector circuit #2 not switching right
- OR (all 1990-) injector output driver not responding
- - check computer, connections
-
- 31 Bad evaporator purge solenoid circuit or driver
- 32 (1984 only) power loss/limited lamp or circuit
- 32 EGR gases not working (1988) - check vacuum, valve
- 32 (1990-92, all but Turbo) computer didn't see change in
- air/'fuel ratio when EGR activated
- - check valve, vacuum lines, and EGR electrical
- 33 Air conditioning clutch relay circuit open or shorted
- (may be in the wide-open-throttle cutoff circuit)
- 34 (1984-86) EGR solenoid circuit shorted or open
- 34 (1987-1991) speed control shorted or open
- 35 Cooling fan relay circuit open or shorted
- 35 (trucks) idle switch motor fault - check connections
- 36 (turbo) Wastegate control circuit open or shorted
- 36 (3.9/5.2 RWD) solenoid coil circuit (air switching)
- 36 (Turbo IV) #3 Vent Solenoid open/short
- 37 Shift indicator light failure, 5-speed
- OR
- part throttle lock/unlock solenoid driver circuit (87-89)
- OR
- solenoid coil circuit (85-89 Turbo I-IV)
- OR
- Trans temparature sensor voltage low (1995 and on; see NOTE 2)
-
- 41* Alternator field control circuit open or shorted
- 42 Automatic shutdown relay circuit open or shorted
- 42 Fuel pump relay control circuit
- 42 Fuel level unit - no change over miles
- OR
- 42 Z1 voltage missing when autoshutdown circuit energized (SEE NOTE #6)
- 43 Peak primary coil current not achieved with max dwell time
- OR
- 43 Cylinder misfire
- OR
- 43 Problem in power module to logic module interface
- 44 No FJ2 voltage present at logic board
- OR
- 44 Logic module self-diagnostics indicate problem
- OR
- 44 Battery temperature out of range (see Note #1!)
- 45 Turbo boost limit exceeded (engine was shut down by logic module)
- 46* Battery voltage too high during charging or charging system
- voltage too low
- 47 Battery voltage too low and alternator output too low
-
- 51 Oxygen sensor stuck at lean position (lean condition)
- OR
- 51 Internal logic module fault ('84 turbo only)
- 52 Oxygen sensor stuck at rich position (SEE NOTE #5!)
- OR
- 52 Internal logic module fault ('84 turbo only)
- 53 Logic module internal problem
- 54 No sync pickup signal during engine rotation (turbo only)
- OR
- 54 Internal logic module fault ('84 turbo only)
- 55 End of codes
-
- 61 "Baro" sensor open or shorted
- 62 EMR mileage cannot be stored in EEPROM
- 62 PCM failure SRI mile not stored
- 63 Controller cannot write to EEPROM
- 64 Catalytic converter efficiency failure
- 65 Power steering switch failure
-
- 88 Start of test (not given on most computers)
-
-
- NOTE #1.
-
- The power module has an air-cooled resistor which senses incoming air
- temperature. The logic modules uses this information to control the field
- current in the alternator. This code applies ONLY to alternators whose
- voltage is computer regulated. If you lose the feed to keep RAM
- information stored
- when the engine's off, you also lose battery voltage sensing. -- Bohdan Bodnar
-
- NOTE #2
-
- From the 1995 TRUCK manuals: the trailer towing package includes a
- transmission coolant temp sensor while the standard package doesn't.
- This may cause the low (no) voltage indication. -- J.E. Winburn
-
- NOTE #3
-
- Matt Rowe comments: The throttle
- postion circuit tells the computer how far the accelerator is depressed.
- The Throttle Position Sensor (TPS) is on the throttle body on
- the opposite side of the throttle cable. The connector should
- have a round rubber cover over the connections. Clear the fault
- codes, start the car and try jiggling the wires/connectors to try
- to trip a fault code. Loss of this signal could cause other problems.
-
- NOTE #4
-
- During cranking, the computer will test the current through the
- injector to see whether there's too much resistance in the injector's
- path. If there is, code 26 is set.
- The problem may be cured with tuner cleaner on the connectors.
- For TBI engines, the injector's cold resistance should be between
- 0.9 and 1.2 ohms (specs vary with year). This is a peak-and-hold
- injector. With the engine idling the
- peak period should be about 1.2 milliseconds whereas the hold period
- will vary. If it's lower than this at idle, then the injector's shorted or
- there's a defect in the injector driver circuit. (Bohdan Bodnar)
-
- NOTE #5
-
- Wade Goldman wrote: In my case, the breather tube leading into the
- catalytic converter had rusted and become detached. This some how would
- cause the sensor to read an over rich condition and run crummy. I did not
- trust the reliability of the weld over a corroded surface and opted for
- the more expensive route of replacing the converter, breather tube and all.
-
- NOTE #6
-
- The Z1 voltage is the voltage of the circuits fed by the autoshutdown
- relay. This typically includes fuel pump and switched-battery feed to the
- ignition coil(s). In my Le Baron, the Z1 circuit leaves the power module
- and splits into two paths: the fuel pump and the positive side of the
- ignition coil. Internal to the power module is the auto shutdown relay (in
- my case, it's a sealed box about 1" by 1"). The output voltage is
- monitored to determine whether the relay responds correctly. I suspect
- that the ASD relay (and, therefore, the Z1 circuit) also feeds the fuel
- injector(s) driver(s) and current sensing circuit, but can't prove this.
-
- I've used the Z1 voltage to test for good power connections to the power
- module. I connected my OTC 500 multimeter from the battery's positive post
- to the ignition coil's switched battery terminal and measured the voltage
- drop using the bar graph to monitor peak voltages. Voltage spikes of
- around 200 mV to 300 mV are ok -- anything more means tv tuner cleaner time
- (or replacing the power module). Another thing to check is the maximum
- voltage drop during the priming pulse. With the old power module, I was
- losing about 2 volts across the circuit; the replacement is losing about
- 1/4 volt. (Thanks, Bohdan Bodnar)
-
- **************** CLASSIC CAR TROUBLESHOOTING ****************
- (1950s-some 80s)
-
- FOR MORE, VISIT http://www.allpar.com/fix/vintage.html
-
- Many of these were taken from the A-Bodies site at http://www.valiant.org/
-
- C1. Won't start (<Dave>):
-
- Check the ballast resistor. It's a little white block attached to the
- metal between the engine and the driver, with a single bolt; wires plug
- into each side. It's easy to replace and under $5.
-
- If the starter makes a rapid clicking noise, your battery may be worn, even if
- you can see your headlights.
-
- If the engine was wet, dry it, separate the wires, and try again, Use
- silicone spray or "wire drier" or, better yet, replace your wires with
- really good ones ($25-40 mail order). These will probably improve your gas
- mileage and power as well.
-
- Dan Stern adds: Whitaker's Multi-Mag comes in the same colors and
- insulation materials as original, but uses the spiral-wound
- construction that you find in wires such as Accel and Jacobs. Lower
- resistance, but no irritating radio noise. They have a lifetime guarantee
- and don't cost more than regular carbon-string type wires. The
- Slant-6 wire set (32605 for pre-75) has the correct 1-piece moulded
- plug boots. They are also sold under the Borg Warner/BWD KoolWire name.
- -----------------------------------------------------------------------
- C2. Anything from pollution to loss of power (<Dave>)
-
- This may be caused by leaking vacuum hoses or mechanics
- disconnecting your vacuum hoses. If you like to breathe, and you want
- your car to perform well, replace all of the vacuum hose -- it costs
- maybe 10 cents per foot. Just get a few yards and do
- it one day (warning: you may need different kinds or sizes. You may need to
- take
- bits of the old stuff into the shop). Make sure hoses are not kinked.
-
- Vacuum leaks caused by leaking hoses that look okay to the naked eye may
- result in the following diagnoses by mechanics:
- * Need new carburetor
- * Need new transmission
- * Need new engine
- * Need valve job
- * Need new mechanic.
- -----------------------------------------------------------------------
- C3. Stalling (<Dave>)
-
- See the above section on vacuum hoses. Turning the cold or warm idle
- screw on the carburetor is a quick fix that doesn't solve the real
- problem. If the car stalls when cold, lubricate the choke well. If it
- stalls when wet, try getting much better ignition wires (lifetime
- warranty, good brand, about $30). Also try:
- * Put window insulating tape (foam) over the top of the electronic
- ignition module
- * Spray the little wires with silicone spray or wire drier
- * Check for vacuum leaks (see above).
- -----------------------------------------------------------------------
- C4. Windshield wipers won't work ():
-
- Put window insulating tape (foam) over the top of the wiper motor.
- -----------------------------------------------------------------------
- C5. Water leaks into the car:
-
- A problem on many A-bodies (Valiant/Dart group). May be solved by keeping
- the cowl (that grille between the hood and windshield) free of leaves and
- gunk, and by straightening out and emptying out the air conditioner
- condensation drain. The black tube that carries a/c water may be seen on
- the firewall (the metal between the engine and the driver). It is small and
- behind other stuff. Sometimes the end of this black tube freezes to itself
- and must be opened with a knife or razor.
-
- See http://www.allpar.com/a/water.html
- -----------------------------------------------------------------------
- C6. runs rough cold, seems to improve with heat
-
- George Young suggests:
- 1) Not enough voltage from old damp coil? - new coil.
- 2) EGR valve plunger binding open?
- - remove and plug manifold vacuum hose to EGR circuit.
-
- Dave adds: Better wires, high quality rotor/distributor cap for
- best fit. Check the stove, that big metal thing on many engines that feeds
- warm air from the engine to the air intake through a usually-rotten or missing
- hose. The vacuum-operated flap may also not be functioning for one reason or
- another, usually a bad vacuum hose. This is common. Dan Stern notes the flap is
- controlled by the Thermostatic Air Cleaner vacuum motor...
-
- George Young adds: My old 318 ran rough when cold and
- wet, would stall out until warm. Choke was the problem. Manifold
- carboned up and wouldn't pass heat to choke coil thermostat. Changed to
- manual choke and no more problem and increased gas mileage
-
- Dan Stern noted that driveability problems could be caused by a bad choke
- heater
- control unit, which may short out and shunt full power to the electric choke,
- causing it to heat up prematurely.
- -----------------------------------------------------------------------
- C7. Lean-Burn (computer-controlled carbureted engine) rough idle
-
- 1). Are your coolant temperature sensor connection ok? If not, the
- computer will see a cold engine and will run rich.
- 2). Are the oxygen sensor connections ok?
- 3). Is the heated air inlet operating correctly?
- 4). Vacuum leaks? Check all vacuum hoses with a religious fervor!
- The leak's location many not even be obvious!
- 5). Carburetor problems: float low? valve seat damage? I doubt the
- latter since it appears that the problem arose quite suddenly. The
- following is something I've used on computer-controlled carbureted
- engines many times: 1). Connect a high impedance dwell meter to the
- mixture control solenoid, set the meter to the 6 cylinders scale, run
- the engine around 2000 rpm until hot and see the dwell. If the a/f
- mixture's ok, you'll see the dwell oscillating about 30 degrees. Low
- dwell with oscillations => a/f mixture lean and running closed loop.
- High dwell with oscillations => a/f mixture rich and running closed
- loop. Dwell at or below 10 degrees => system stuck lean. Dwell at or
- above 50 degrees => system stuck rich. The latter two extremes indicate
- closed loop operation since open loop operation typical will show a
- stable dwell reading between 20 and 30 degrees (usually, closer to 20).
- Do not do this test at idle since some engines will be operated in open
- loop at idle REGARDLESS of the coolant temperature sensor's output.
- Incidently, I've just outlined the procedure for GM's "System
- Performance Test" which is used on GM C3 carbureted engines.
- -----------------------------------------------------------------------
- C8. Gas gauge acts funny: See #34. (part 4)
- -----------------------------------------------------------------------
- C9. Stalling or poor idle - wet weather / snow -- see #39 (part 4)
- -----------------------------------------------------------------------
- C10. Slant Six problems
-
- Cold driveability problems tend to stem from poorly
- adjusted choke and choke pulloff, bad accelerator pump, and sloppy carb
- rebuilds
- (Carter BBS one barrel is better than Holley 1920.)
- Other big driveability problem source is the fact that the vibration
- damper outer ring tends to slip, which makes the timing mark WAY OFF. Which
- means timing would never be accurately set. Also check for timing chain
- stretch.
-
- Check by putting the engine at #1 TDC - top of compression stroke (both valves
- closed) and see where the timing mark is. There are companies that re-bond
- dampers with new silicone material. I think one is called Damper Dudes,
- out of
- California. I don't know if this happens on other CC engines. Basically, if
- your damper has an inner hub and an outer ring sandwiching rubber bonding
- material, this can happen.
-
- -----------------------------------------------------------------------
- C11. 318 V8 troubleshooting
-
- Bruce Martin wrote:
- One very common fault with the otherwise wonderful 318 is that the
- exhaust crossover in the intake manifold (which warms the base
- of the carb) becomes clogged. This is common so it should be
- among the first things you check. (This problem was addressed on the
- Magnum engines)
-
- CURT PINCK wrote:
- It is interesting the wide variety of timing specs given for the 318, all the
- way from 2 degrees ATDC to 16 degrees ATDC, depending on the type of engine
- and
- vehicle...Most books recommend not to try to time by ear, even if you have
- experience doing this.
-
- Ted Devey adds two more steps:
- 1. examine the reluctor teeth in the distributor for possible damage,
- nicks etc. which can happen if the gap gets too small. If there is damage
- to the
- teeth, replace the reluctor.
-
- 2. Several years ago I dismantled the Carter 2-barrel carburettor and
- reassembled it with the jet assembly upside down. There is no obvious wrong
- way.
-
- -----------------------------------------------------------------------
- C13. Seat belt looseness
-
- During the late 70's up through the late 80's all American cars had
- something called a window shade mechanism to allow for a small amount of slack
- to build-up in the shoulder belt. This was to prevent people from complaining
- that their belts were too tight. I experienced (ref:June '87 Car and Driver
- article by Patrick Bedard) a problem where the seatbelt built up too much
- slack.
- Sometimes the belts, like a windowshade, would never return at all. There is
- usually a large plastic button on the 'B' pillar that needs to be fooled into
- thinking the door is always opened, which by the way disables the window shade
- mechanism and is how the belts return 'home' when you get out of the car.
- Cut
- the plastic button very close to the 'B' pillar, being careful not to cut into
- the inner spring
- Take a cotter pin and put it through the loops of the spring, this
- prevents the
- spring from ever retracting. Chrylser mini-vans are easier in that they
- have a
- rotating plastic cam with a striker pin that is engaged by the closing door.
- Just cut the striker pin and you eliminate the problem.
- -----------------------------------------------------------------------
- C14. Low front end
-
- Many late 60's and early 70's A-body Chrysler products had a problem
- with the rear mount for the torsion bar. Water collects in the channel
- and rust occurs. After a decade or so the channel that the mount is
- welded into rusts through and the mount twists and that side of the
- car falls onto the rebounce (sp?) bumper. If this is what happened you
- will need to find a local frame/suspension/alignment shop that has
- someone who has welded in new material to replace the rusted stuff and
- then realign the ride height when done. (Thanks, Chris Jardine).
-
- -----------------------------------------------------------------------
- C15. Pinging on V-8s
-
- Pete O Dickerson wrote: My 75 Dodge Swinger 318 would ping at part throttle
- operation, not at full throttle (floored!) like you might expect. Just going
- over an overpass or up a hill the engine would ping and clatter, even
- though the
- ignition timing and carburetor were set correctly.
-
- The manifold was made from cast metal. The molten metal was poured into a
- mold
- through a little hole and when the manifold was finished, the little hole was
- plugged up with a little rubber plug. Well, after a few years this little
- plug
- would dry up, shrink, and fall out, leaving a hole in the manifold. This hole
- would cause a lean condition to exist at part throttle operation, by
- letting air
- leak in.
-
- Try removing the carb and shining a flashlight down into the manifold and
- seeing
- if there is a hole in the bottom of the manifold. You can either plug it
- up or
- replace the manifold with a more performance oriented unit.
-
- (The maintainer adds: invest in a vacuum gauge, they are cheap!)
- -----------------------------------------------------------------------
- C16: Fast idle, then stalling.
-
- >From Timothy Economou: If you start your car and it runs for a while at fast
- idle and then it starts to load up and then stalls. There is this little
- round
- thing on the open end of your breather that closes the outside air when
- your car
- is at fast idle and lets it draw air from the manifold. (Stove control). Check
- it.
-
- Editor's note: the stove control is frequently bad on vintage vehicles. The
- vacuum hose, control, and mechanics of the flap in the air horn should be
- checked. See above.
- -----------------------------------------------------------------------
-
- =========================
-
- DIAGNOSING PROBLEMS IN COMPUTER CONTROLLED
- CARBURETED ENGINES
-
- From: Bohdan L Bodnar
-
- This is the procedure I've used to diagnose air/fuel
- mixture problems in computer controlled carbureted engines; the
- procedure can also be used to set the idle air/fuel mixture
- without exhaust gas analysis. The procedure is
- based on the General Motors System Performance Test.
-
- THEORY
-
- The a/f mixture is controlled by a MIXTURE CONTROL SOLENOID (MC
- solenoid). This is a valve which operates at a fixed frequency
- (typically, 10 Hz) and whose duty cycle (valve's ON time divided by
- period) is varied. That is, the valve is pulse width modulated. When
- the valve is turned on, the incoming a/f mixture is fully leaned; when
- off, fully enrichened. The former is called a "lean command" whereas
- the latter is called a "rich command." By varying the duty cycle of the
- MC solenoid, the AVERAGE a/f mixture can be varied. In GM products,
- this valve directly varies the incoming fuel and air flow. In Chryslers, only
- the
- incoming fuel flow is directly varied.
-
- The valve has a two wires electrical connector. On wire is connected to
- switched battery voltage whereas the other is connected to a power
- transistor in the computer and is a source of switched ground.
-
- During closed-loop operation the following will occur (assume the oxygen
- sensor is sensing a lean condition -- its voltage will be low):
-
- 1). The computer gradually decreases the MC solenoid's duty cycle.
-
- 2). The exhaust eventually becomes rich enough that the oxygen sensor's
- output will swing high (about 1 volt).
-
- 3). The computer gradually increases the MC solenoid's duty cycle.
-
- 4). The exhaust eventually becomes lean enough that the oxygen sensor's
- output will swing low (about 0 volt).
-
- The cycle now repeats. A device for monitoring the solenoid's duty
- cycle (such as a dwell meter) will show a constantly varying duty cycle.
- The frequency of the oscillations will depend on the how fast the
- computer varies the duty cycle and the engine's RPM. An AVERAGE duty
- cycle of 50% corresponds to, on the average, NO average a/f correction.
- Stated differently, everything is operating correctly. An average duty
- cycle of LESS THAN 50% corresponds to, on the average, a rich command
- (the computer is compensating for a lean condition). An average duty
- cycle GREATER THAN 50% corresponds to, on the average, a lean command.
-
- DIAGNOSIS AND SETTING IDLE A/F MIXTURE
-
- Monitoring the MC solenoid's average duty requires (for most people) the
- use of high impedance dwell meter. A low impedance dwell meter may be
- used unless it affects engine operation; stay away from self-powered
- dwell meters. Following the GM procedure, set the dwell meter to the
- six cylinders scale REGARDLESS of the number of cylinders in the engine.
- At this setting, 30 degrees will correspond to a 50% duty cycle, 60 to a
- 100% duty cycle, and 0 to a 0% duty cycle. Run the engine until closed
- loop operation is present; this will be indicated by a varying dwell
- (see footnote 1 for deviations from this procedure). Once the engine is
- hot, not the average dwell -- the reading should vary equally above 30
- degrees and equally below 30 degrees. The following is a brief trouble
- listing:
-
- 1). DWELL NOT VARYING: system is operating in open loop.
-
- 2). DWELL STUCK AT 10 DEGREES OR LOWER: full rich command is present;
- the computer is compensating for WHAT APPEARS TO BE a massive fuel flow
- reduction (check for dirt in carburetor, air injection system stuck in
- upstream position, vacuum leaks, improper a/f mixture setting...).
-
- 3). DWELL STUCK AT 50 DEGREES OR UP: full lean command is present
- (check for float stuck low, valve seat damage, oxygen sensor's sense
- lead shorted to battery voltage, etc.)
-
- 4). DWELL OSCILLATING, AVERAGE READING IS BELOW 30 DEGREES: average
- rich command is present (check for vacuum leaks, dirt in carburetor's
- jets, improperly set a/f mixture...)
-
- 5). DWELL OSCILLATING, AVERAGE READING IS ABOVE 30 DEGREES: average
- lean command is present. Check for incorrectly set a/f mixture, float
- stuck low, valve seat damage, clogged air filter, etc...).
-
- Based on the above descriptions, it should be fairly clear on how to set
- the idle a/f mixture: merely set the mixture so that the average dwell
- is 30 degrees. Now, suppose the system's dwell is not varying, but the
- sensors are working properly, the upper radiator hose is hot...
-
- Several cars with small engines have the oxygen sensor mounted fairly
- far away from the engines. During idle conditions, the sensor
- may cool off to the point that it will not operate.
- Turn off all electrical accessories (so
- as to provide a minimal load on the engine) and use the idle stop screw
- on the carburetor to gradually increase the idle rpm until the sensor
- begins oscillating. Ensuring a negligible load on the engine guarantees
- that the carburetor will be operating mostly on its idle circuit. Now,
- set the a/f mixture so that the average dwell is 30 degrees.
-
- Note that the a/f mixture setting procedure assumes that NO fuel
- delivery problems (vacuum leaks, clogged carburetor, etc.) are present.
-
- FOOTNOTES
-
- [1] In some engines the a/f mixture is varied REGARDLESS
- of whether the engine is in closed loop operation or not.
- Consider setting the a/f mixture or diagnosing
- at a slightly increased rpm.
-
- **************************************************
-
- 5. REPLACING CRANKCASE INLET AIR FILTERS
-
- If you remove the air cleaner and look at it from the front, the
- breather (crankcase filter) will be in the "box" at the lower right
- side. To get at it, you remove the 8 or so machine screws and the
- bottom of this "box" will fall off. The filter is held in place by a
- crudely placed screen. Lee makes a replacement filter (about
- $2). In my Le Baron, I ended up replacing all the screws with
- self-tapping sheet metal screws since the factory had almost every one
- overtightened. --- Bohdan Bodnar
-
- David Zatz works at http://www.toolpack.com/
-