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FAQ: How to Troubleshoot, Repair & Maintain Hondas and Selected Other Vehicles
Check out these tips and explanations from our Cars & Trucks expert--the best car and truck guy on the net!
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TIP: Being willing and able to safely drop the subframe is crucial to replacing struts, ball joints, front wheel bearings & hubs, steering knuckles, alternators, and sway bars & bushings on many Fords. Become a pro at it and save a bundle.
1. Basic Ignition System Troubleshooting and Engine Control Module (ECM) Test: Overview
Basic Ignition System Troubleshooting
Proper ignition system evaluation begins by answering three basic diagnostic questions:
1. When you turn the ignition switch to ON (Position II), does the Check Engine Light (CEL) come on and then go off after 2 seconds? If not, the problem is with the ACG (ALT) (S) fuse, in the under dash fuse/relay box; ECM (perform the K-Test, below); main relay; or the ignition switch. Perform tests in that order.
2. When the CEL goes out, do you hear and/or feel the Main Relay "click"? If not, repair or replace the main relay.
3. During the 2 second interval that the CEL is on, do you hear the fuel pump in the gas tank run? If not, check the fuel pump.
If the CEL does not go out, most Civics will not spark and the fuel pump will not run. That's why we begin our diagnosis here. Remember, the Main Relay actually contains two individual relays. One relay is energized whenever the ignition is on, which supplies battery voltage to the ECM, power to the fuel injectors, and power for the second relay. The second relay is energized for 2 seconds when the ignition is switched on, and when the engine is running which supplies power to the fuel pump.
Next, test all under hood and under dash fuses with a test light or multimeter. Using a test light or multimeter is faster, more accurate, and eliminates the possibility of replacing a fuse in the wrong slot. This is easy to do in the dark and cramped location of most under-dash fuse boxes. After all fuses are tested, check for any Diagnostic Trouble Codes (DTCs). Ignition components that usually cause Hondas to unexpectedly die or not start are (listed in order): ignitors, main relays, coils, and ECMs. MAP Sensors cause some problems, but not often. In my opinion, all of these key ignition components, including the ECM, should be replaced from a preventive maintenance standpoint every 120,000 miles or 10 years, whichever comes first.
Engine Control Module (ECM) Test
The ECM (computer) is nothing more than a “power transistor,” whose job is to supply the proper voltage to a host of sensors, under constantly varying conditions. Unlike some websites that claim, “Of the million or so vehicles American Honda and Honda Canada sell each year, maybe five or six (yes, that’s right: 5 or 6) come back with actual bad computers. All the rest of the returned ECMs test good by Honda, and were replaced in error. Unless the computer has got damaged by flood, other moisture intrusion, impact, or serious electrical overload, the probability of the computer being bad is virtually zero. Honda computers are exceedingly reliable. Do not waste your money replacing them. Your problem almost certainly lies elsewhere,” I have seen many Honda ECMs that have had to be replaced at AskMeHelpDesk.Com, including mine. The statement that the probability of a computer being bad is "virtually zero" caused me a lot of trouble, because it is so adamant. It is categorically wrong and misleading.
Here’s a typical situation, which, by the way, was my own. The engine cranks but will not start. The CEL stays on, along with the oil and battery lights. When the Service Check Connector terminals are jumped with a paper clip, the CEL does not indicate any DTCs. You hear the first click from the Main Relay’s first relay, but not the second and third click from the main relay’s second relay. You do not hear the fuel pump run for 2 seconds and there is no spark at the plugs. In other words, you have catastrophic system-wide failure. This is a particularly intimidating problem with a simple test. It’s a simple test, however, with a lot of logic behind it. Let me explain.
After considerable analysis, I realized that the Manifold Absolute Pressure (MAP) Sensor is the “key” sensor on Hondas. It controls timing (similar to the old vacuum advance on distributors) and air/fuel mixture, depending upon manifold pressure changes. Like any transducer, it converts energy from one form to another. Here, it converts throttle body vacuum pressure changes into fluctuating electrical current signals to the ECM. If this sensor does not receive the proper voltage from the ECM, you will experience catastrophic ignition and fuel system failure. Therefore, I reasoned, begin the diagnosis by testing the voltage between the ECM and the MAP Sensor, because it’s a showstopper if this sensor does not receive the proper voltage. The result is the awesome “K-Test” and it WORKS beautifully!
The K-Test: Remove the MAP Sensor connector and turn the ignition switch to ON (Position II). Using a multimeter, check for 5 volts going between the MAP Sensor connector's reference wire (+) and ground. As you look at the connector, this is the socket on the right. Really press the black test lead into a cleaned main ECM ground on the thermostat housing. If the voltage is low, it’s probably indicating ECM failure. Most failed ECMs will record a fraction of a volt. To me, the K-Test is simple, elegant, and accurate.
The confirming test is to turn the ignition switch OFF, disconnect the D harness to the computer, turn the ignition switch ON, and measure the voltage between computer pins D19(+) and D21(-). If there is less than approximately 5 volts, substitute a known good ECM. If you have approximately 5 volts between D19 and D21, repair an open between the ECM and the reference wire going to the MAP Sensor. After much experience with the K-Test, I wouldn’t bother running the confirming test anymore.
When you remove your ECM, disconnecting the negative battery terminal first, look at the likely heat discoloration on the metal covers. You will probably observe a spiral blue pattern. ECMs don’t have fan motors to cool them and, to make matters worse, are covered by carpeting. Heat, vibration, flooding, and shorts, among other things, reduce their lives. I could tell heat crazed the microprocessors in my ECM. I was told by an ECM remanufacturer that the electrolytic capacitors in 1989-94 Civics are known for leaking. Until now, too many main relays, ICMs, and coils have been unnecessarily replaced for computer-related “crank but won’t start situations.”
Idle speed adjustment is not straightforward. The idle adjusting screw is located on the end of the throttle body and is often “leaded in,” to prevent people from fiddling with it. Take a small screwdriver and dig it out. Also, locate the blue tachometer wire, which goes to the distributor. Actually, it is connected to the igniter inside the distributor. The tachometer wire is buried, with a protective rubber cover over it, in a cluster of wires near the clutch master cylinder reservoir. Take a small screwdriver and carefully pry the connector from the rubber cover, using the small hole provided for this purpose.
1. Start the engine and warm it up to normal operating temperature.
2. Turn engine off and connect the tachometer to the blue tachometer wire.
3. Disconnect the 2P connector from the Idle Air Control (IAC) valve.
4. Start the engine with the accelerator pedal slightly depressed. Stabilize the rpm at 1000, then slowly release the pedal until the engine idles.
5. Check idle in a no-load condition; i.e., headlights, blower fan, rear defogger, radiator fan, and air conditioning turned OFF. Adjust “Initial Idle Speed” to 450 rpm, by turning the idle adjusting screw.
6. Turn the ignition switch OFF.
7. Reconnect the 2P connector to the IAC valve, then remove BACK UP (7.5 A) fuse in the under-hood fuse/relay box for 10 seconds to reset the ECM. Make sure to record any radio codes first.
8. Restart and idle the engine in a no-load condition for one minute. Verify that the “Final Idle Speed” is around 700 rpm.
1. Start the engine and warm it up to normal operating temperature.
2. Adjust “Final Idle Speed” to 700 rpm, using the idle speed adjustment procedures above.
3. Turn off engine and all electrical systems.
4. Jump the Service Check Connector (SCC) with a paper clip.
5. Connect positive inductive timing light lead to the positive battery terminal.
6. Connect negative inductive timing light lead to engine ground.
7. Connect inductive timing light lead to the No. 1 spark plug wire.
8. Start engine.
9. Using the timing light, rotate the distributor, after loosening the three 12 mm mounting bolts, until timing is set to 16 degrees BTDC* on the crankshaft pulley. 16 degrees BTDC should be the middle of the three clustered hash marks on the pulley. Align middle hash mark on pulley with pointer above. You may want to take chalk or yellow paint and highlight the hash mark first.
10. Button everything up.
11. Remove the BACKUP fuse for 10 seconds, in order to reset the computer. Record any radio codes first.
On most 4-cylinder Civics and Accords, the starter motor is located on the passenger's side of the transmission, just beneath and to the rear of the distributor. The large starter motor cable, from the positive battery terminal, goes right to it.
1. Disconnect the negative battery cable.
2. Disconnect the starter cable from the "B" terminal on the solenoid, then the BLK/WHT wire from the "S" terminal.
3. Remove the two bolts (14 mm) holding the starter; then, remove the starter. A 3/8-inch drive ratchet wrench or breaker bar, with a 6-inch extension, usually does the trick. Spray both bolts with PB Blaster, Kroil, or Liquid Wrench first.
4. Install in the reverse order of removal.
NOTE: When installing the starter cable, ensure the crimped side of the ring terminal is facing out. It's a good idea to clean both terminals and connectors with #240 abrasive cloth, or steel wool, and coat with dielectric grease.
1. Oil and Filter--Use full-synthetic 5W-30 engine oil; e.g., Mobil 1, Pennzoil Platinum, Amsoil, and Valvoline SynPower. Change oil and filter every 6,000 miles or 6 months, whichever comes first, while the engine is hot. Use a premium oil filter (e.g., Mobil 1 EP, Amsoil Ea, or Purolator PureOne).
2. Manual Transmission Fluid--Amsoil Synthetic Manual Synchromesh Transmission Fluid (5W-30). Change every 30,000 miles, while the transmission is hot.
3. ATF--Mobil 1 Synthetic Multi-Vehicle ATF or Amsoil Universal Synthetic ATF. Change every 30,000 miles, along with filter (where applicable), while the transmission is hot.
4. Coolant--50/50 mixture of automaker approved antifreeze and distilled water. Distilled water is super important. Change every 2 or 3 years, while the engine is cold.
5. Brake/Clutch fluid--Valvoline SynPower or ATE TYP 200 Brake Fluid. Change every 2 years. This is particularly important to do on anti-lock brake systems, in order to prevent corrosion from developing. Corrosion can tear the seals apart inside brake systems and result in "eye popping" repair bills. I use the fool-proof Brake Bleeder Economy One-Man, Cal-Van Tools, No. 247, brake bleeder for both applications. It cost $2.99 and has a one-way check valve. Here's a similar, and more widely available, product from Harbor Freight:
Changing the brake fluid every 2 years is the key to trouble-free brakes and clutches.
6. Power Steering Fluid--Change fluid every 60,000 miles, due to the high expense associated with replacing pump, gearbox and valve body unit. More heat is developed in power steering units than most people realize. Only use Honda Genuine HG Power Steering Fluid, Part No. 08206-9002, or Amsoil's Synthetic Universal Power Steering Fluid (PSF), in Hondas. They must be Honda-specific. Using other fluids, such as ATF or other manufacturer's standard power steering fluid, will damage the system.
7. Air Filter--Change every 30,000 miles or 24 months, whichever comes first.
8. Fuel Filter--Change every 60,000 miles or 48 months, whichever comes first, after depresurizing the fuel system and disconnecting the negative battery cable (record radio codes first).
9. Spark Plugs--Only use NGK spark plugs on Hondas. Change regular plugs every 24,000 miles or 24 months, whichever comes first, while the engine is cold. Change platinum plugs every 45,000 miles or 36 months, whichever comes first. Remove and replace plugs at least every 36 months, to prevent seizure in the aluminum head.
10. PCV Valve--Change every 60,000 miles or 48 months, whichever comes first.
11. Distributor cap, rotor--Replace every 60,000 miles. I prefer BWD distributor caps and rotors. Besides coming with a lifetime warranty, BWD distributor caps have brass contacts inside, which don't corrode and erode as fast as the aluminum contacts on Honda distributor caps.
12. Ignition wires--Replace every 80,000 miles.
13. Timing belt, belt tensioner, and water pump--Replace every 90,000 miles or 7 years, whichever comes first. On Accords, also replace the camshaft seals.
14. Main relays, ignitors, coils, and ECMs--Replace every 120,000 miles or 10 years, whichever comes first. I chose a Cardone remanufactured ECM from O'Reilly Auto Parts (Lifetime Warranty).
15. Fuel injector cleaner--Add every 4 months. I recommend Shell Regane or Chevron's Techron Concentrate Plus, which claims one tankful can even clean and protect against sulfurs that can harm gas gauge sensors.
16. Clean fuse and relay contacts--Due to corrosion, it's not uncommon for fuses and relays to be good but not pass current, particularly in trucks. To prevent this, disconnect the negative battery cable (after recording any radio codes), clean contacts to each fuse and relay with No. 240 abrasive cloth, or steel wool, and lightly coat the contacts with dielectric grease. Do one fuse and relay at a time, in order to not replace them in the wrong slot.
17. Clean battery and starter motor connections--Disconnect the negative battery cable first (after recording any radio codes), clean connections with a battery terminal brush, No. 240 abrasive cloth, or steel wool--afterwards, lightly coat connections with dielectric grease. Reconnect the negative battery cable last.
The objective is to maintain "like new" performance for years and years. A well-maintained Honda should be able to go 350,000 miles.
1. Oil pan plug (17 mm)--torque to 33 lb.-ft. (Honda)
2. Oil filter (Honda)--torque to 16 lb.-ft., using a cap wrench.
3. Spark plug anti-seize compound--use a half pea-size drop (preferably high-temperature nickel anti-seize) on lower threads, allowing rotation to spread. If you use too much, plugs will "coke" in the holes. Remove old plugs when the engine is "stone" cold, to decrease the chance of stripping the aluminum head. Since anti-seize compound is a lubricant, reduce specified torque by 20% to prevent over-torquing and stripping threads.
4. Use a battery squeeze bulb to partially change the power steering fluid in the reservoir each year. Only use Honda Genuine Power Steering Fluid or Amsoil's Synthetic Universal Power Steering Fluid (PSF).
5. Premium oil filters, such as PureOne, have a silicone rubber anti-drain back valve that makes a real difference in preventing oil from draining overnight from horizontally mounted filters (Honda). This provides much quieter valves at startup and less wear. These new premium filters (e.g., Mobil 1 EP, Amsoil Ea, or PureOne) are worth the money, in my opinion. Filtration is rightfully the new "big thing" in lubrication.
6. Always change engine oil and transmission fluid, when the engine is hot. This allows a faster and more complete drain. If you change the oil when the engine is cold, dirt will cling to the sides of the block and pan.
7. Fuel filter changes are grossly overlooked by many people. This increases the chance of burning out the fuel pump motor and contributes to poor performance and idle.
8. Buy the best full-synthetic lubricants you can find for your engine and transmission. I focus on European oil standards and buy 5W-30 engine oil that is ACEA A3 rated and MB 229.3 or MB 229.5 rated for my vehicles. If you take care of these two items, everything else is relatively minor. Pay particular attention to automatic transmissions, which are more involved and problematic than engines these days.
9. To safely remove varnish and sludge from an engine or transmission, use Auto-Rx.
10. Maintenance Log--record "Date, Mileage, and Work Performed." Refer to it often. I use Microsoft Word and keep a Maintenance Log for each of my vehicles in my PC--it's incredibly handy and facilitates staying on top of maintenance.
1. Recommended Home Air Conditioner Maintenance--Free Special Bonus
I realize this posting does not really fit in the "Cars & Trucks Section." Yes, it's a little funky. This is to keep everything a little weird. Consider it a free bonus, covering secrets of the trade. However, I thought many Cars & Trucks do-it-yourselfers would find it of particular interest. There's a lot of money and aggravation to be saved by following these recommendations. HVAC information for the do-it-yourselfer is hard to come by--it's a protected turf. Many HVAC companies intentionally use "proprietary" parts, with no cross-reference to other brands. This is a key part of their strategy to prevent competition. Proprietary parts, licensing, part distribution control, and lack of DIY servicing information is how the industry protects itself.
1. Ensure outdoor condenser unit is level in both directions.
2. Pour 8 parts water to 1 part bleach down the evaporator coil drain pipe 4 times per year, to prevent mold from developing.
3. Replace air filter monthly. This prevents dust buildup on the evaporator coils, which interferes with proper airflow and can cause icing problems.
4. Clean outdoor condenser coils in early April of each year with a garden hose. Remove front and side condenser coil covers and gently hose away dirt, grass, and debris. Straighten any bent fins with a fin comb. Don’t cut the grass around the condenser unit, while it is running.
5. Remove high voltage cover plate and clean area of dirt, fire ants, and spiders each year. Fire ants and spider webs are dielectric and can prevent the contactor from working. Examine wiring for burning and capacitors (on single phase current units) for leakage and swelling. In order to check condenser capacitance, all wires must be removed first. Spread fire ant chemicals around condenser unit to keep ants from globulating on the contactor. They are attracted to 60 Hz current. Spray connectors with WD-40, making sure not to get any on the contactor's contacts.
6. Oil both condenser fan motor ports with 15 drops of ISO 32 (10 wt.) turbine oil each year. A 4 oz. Zoomspout Oiler from ACE Hardware costs $1.65. The finest synthetic lubricants, which I use, are Mobil SHC 624 and Amsoil RCH05.
7. Replace contactors (relay) proactively every 6 years. This is at the heart of properly maintaining an air conditioner and is the most overlooked preventive maintenance step. Some HVAC technicians will recommend replacing the whole outside condenser unit ($1,500), when only the contactor ($15) needs replacing. When contactor points open and close, they become pitted. As the cross-sectional area of the points gets cut in half, the resistance goes up by a square function (four fold). [Remember the formula for calculating the area of a circle = pi x r (squared)] This results in the compressor motor becoming starved for electricity, which causes it to work less efficiently and can burn it up.
Method: While the old contactor is still mounted, "crack loose" the four 5/16" hex-head bolts securing the main "line" and "load" wires. Using a 5/16" nut driver, remove the two hex-head mounting bolts to the old contactor, mount the new contactor, and then replace wire-for-wire from the old contactor to the new contactor. Use a pair of needle nose pliers and a small screwdriver to assist you in removing and replacing wires. Sit on a chair and take your time, while you perform this task.
In some areas of the country, HVAC supply houses won't sell to you, unless you work in the industry. It's a different story online. Here's what contactors look like:
8. Replace digital thermostat alkaline batteries every 2 years. Low batteries can play havoc with the thermostat and cause dangerous inadvertent Locked Rotor Amperage that can damage contactors and compressor motors. Ensure your thermostat has an anti-short cycle feature, which can save your unit when the power goes off and then slams back on.
9. Obtain documentation on your air conditioner, while you can. Wiring diagrams and functional unit part lists are often in a plastic bag behind the high voltage cover to the condenser unit. It's invaluable data that will be destroyed by weather, if you don't get to it first. Keep the original in the house and replace a copy in the condenser unit. Record the data on the metal tag on the condenser unit--a lot of valuable data is even embedded in the model number;e.g., TTP036C100A2. Since there are 12,000 BTUs per ton, digits 5 and 6 tell us that this is a 3-ton unit.
10. Check system cooling. As long as the temperature differential between the air coming out of the air duct closest to the furnace and the air return duct is at least 15 degrees Fahrenheit, then the freon level is probably fine. An additional check is to feel the large, low pressure, insulated return line to the compressor--it should feel cool and have condensation on it.
11. Obtain a Fluke Model 16 HVAC digital multi-meter to check capacitors, temperatures, and other items. It also happens to be about the best DMM for diagnosing automotive electrical systems. A properly maintained air conditioner should last 25 to 30 years.
12. Remove filter and vacuum the air return area, which is underneath or leads into the furnace. On most units, this can be accomplished by removing the return air vent and vacuuming the inside area. This will increase air flow, by substantially reducing the amount of dust and lint that will be trapped by the filter. Finally, take your vacuum and/or air compressor and blow all dust away from the blower motor vents. Dust will collect and interfere with the proper cooling of the blower motor. It also can be a fire hazard.
13. Wax your condenser unit, when you wax your car.
Turn the thermostat OFF, pull AC disconnect to condenser unit, and turn off furnace breaker (power to contactor coil) before performing any work. Use non-contact voltage meter to verify power is off. Finally, use a large plastic handle screwdriver between contactor and ground to confirm power is off.
14. Install Delay on Break (DOB) Timer. Anti-short cycle timers protect compressor and contactor from high Locked Rotor Amperage (LRA) damage, when lightning or other power outages cause power to slam off and then back on. Popular products include ICM 203B, which is adjustable from 2 seconds to 10 minutes. 5 minutes is usually sufficient to allow internal compressor pressures to equalize. Remove wire from contactor coil and attach to Terminal 3 (Input) on DOB Timer. Connect jumper wire from DOB Timer Terminal 1 (Load) to contactor coil.
Trick:Take a small flashlight and and figure out how the oxygen sensor's 4-wire pigtail connector comes apart--don't force it. Frequently, the trick is to gently separate the connector from the bayonet mount first; then, it easily comes apart or it's apparent how it unlocks. Honda connectors can be tricky and give some do-it-yourselfers a fit.
Remove heat shield, spray old oxygen sensor with PB Blaster or Kroil (let it sit for a while), spray with PB Blaster or Kroil again, warm-up car for several minutes, and use a 15-inch breaker bar on the end of a 22 mm oxygen sensor socket to remove sensor. Afterwards, clean threads thoroughly with brake cleaner, allow to sit for quite a while and "air out," and install new oxygen sensor with anti-seize compound. Good cleaning technique is a must. Tighten to 33 lb-ft or 4.5 kg-m. Lightly coat heat shield bolts with anti-seize compound, before reinstalling the heat shield.
I am not a fan of universal oxygen sensors or those made by Bosch for Civics. I recommend Denso sensors. Over time, you want the best sensor or you will pay for it in poor gas mileage and performance. Oxygen sensors are EXTREMELY sensitive to anything, particularly silicone spray, RTV sealers, WD-40, or any oil on the pigtail connector. Don't even use non-chlorinating brake cleaner or electrical contact cleaner on oxygen sensor connectors. NEVER use any of these products around the oxygen sensor or pigtail connector. If you do, the ECM will keep throwing a code forever, once the engine warms up and is out of "open loop" mode. Remove pigtail connector and gently dress the male and female connectors with jeweler files, if you suspect any contamination.
After replacing the oxygen sensor, on OBD-I vehicles, clear the Check Engine Light by removing the Back Up (7.5 A) Fuse in the under hood fuse box, or by disconnecting the negative battery cable, for 10 seconds to reset the ECM. On OBD-II vehicles, use a code reader or scan tool to reset the ECM.
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