Check out these tips and explanations from our Cars & Trucks expert--the best car and truck guy on the net!

Of course, you're also welcome to post questions to this board for more information: Just click the "Ask about Cars & Trucks" button (NOT the Answer this Question button) at the top of the page. Be sure, though, to check the list below to see if your issue is already covered.

Members: Please do not post replies in this thread. If you have a question, click on the Ask About Cars & Trucks button above.

TxGreaseMonkey

22. Honda Idle Control System

Idle speed is controlled by the Idle Air Control Valve (IACV). The IACV changes the amount of air being bypassed to the intake manifold, in response to electric current controlled by the ECM. When the IACV is activated, the valve opens to maintain proper idle speed.

Symptom and Subsystems to Check:

1. Difficult to start engine, when cold--check Fast Idle Thermo Valve.

2. Fast idle out of spec, when cold:
a. Check Fast Idle Thermo Valve.
b. Check IACV.
c. Check idle adjusting screw (see Section C).

3. Rough idle:
a. Check hoses and connections.
b. Check IACV.

4. RPM too high, when warm:
a. Check IACV.
b. Check Fast Idle Thermo Valve.
c. Check hoses and connections, check Power Steering Pressure Switch Signal, and check idle adjusting screw.

5. RPM too low, when warm:
a. Idle speed is below specified rpm, with no load--check IACV and idle adjusting screw.
b. Idle speed doesn't increase after initial start up--check IACV.
c. Idle speed drops in gear (automatic transmission)--check automatic transaxle gear position switch signal.
d. Idle speed drops when AC is on--check air conditioning signal and IACV.
e. Idle speed drops when steering wheel is turned--check power steering pressure switch signal and IACV.
f. Idle speed fluctuates with electrical load--check hoses and connections, IACV, and Alternator FR Signal.

6. Frequent stalling, while warming up--check IACV and idle adjusting screw.

7. Frequent stalling, after warming up--check idle adjusting screw and IACV.



Additional Steps:

. Check Alternator FR Signal. Have alternator inspected, if idle speed fluctuates with electrical load. The FR signal communicates to the ECM how "hard" the alternator is working to meet the electrical demands of the car, including the battery and any loads which aren’t monitored by the ELD. This square-wave signal varies in pulse width, according to the load on the alternator. The ECM places, approximately, 5 reference volts on the wire. The voltage regulator will drop this signal to approximately 1.2 volts, in proportion to alternator load. The ECM compares the electrical load (ELD) signal with the FR (Charging Rate) signal from the alternator and uses that information to set the idle speed and turn the alternator on and off. This helps fuel economy.

. Clean main ECM ground on thermostat housing.

. Reset ECM, by removing the 7.5 amp Back Up Fuse, in the under-hood fuse box, for 10 seconds.

. Replace Engine Coolant Temperature (ECT) Sensor, which affects fuel injector pulse width. It's located on the thermostat. The ECT Sensor is a temperature dependant resistor (thermistor), whose resistance decreases as the engine coolant temperature increases. It provides a richer mixture when cold, leaner mixture when hot.

. Replace PCV Valve, cleaning hose with brake cleaner spray.

. Substitute a known-good ECM. If symptom goes away, replace original ECM.

TxGreaseMonkey

5. Preventing Coil-On-Plug (COP) Problems

Many repair shops are reporting a large number of coil-on-plug (COP) failures with engines. The majority of problems are related to 1) customers washing their engines, or 2) body repair shops hosing off engines after repairing hood hail damage. Water seeps into the spark plug hole, where engine heat converts it to steam, and damages the coil.

Here are some rules to prevent the problem:

1. Never wash the engine, unless you cover the coils.

2. Always replace spark plug boots, when you change plugs.

3. Always replace the spark plug, when you replace a coil.

4. Always apply silicone dielectric grease to the rubber seal on the coil, where it connects to the engine; e.g., Motorcraft Silicone Brake Caliper Grease and Dielectric Compound (XG-3-A).

TxGreaseMonkey

23. Cleaning Idle Air Control Valve (IACV)

In order for Hondas, and many other modern-day cars, to idle properly, the IACV needs to be cleaned. Here's how to perform this simple task:

1. Remove IACV electrical connector.

2. Remove both bolts (12 mm) securing IACV to plenum.

3. Remove both IACV hoses.

4. Clean IACV and hoses with a spray can of brake cleaner--be sure to wear safety goggles.

5. Install new O-ring, if necessary.

6. Remove air intake from throttle body. Ensure upper and lower throttle body ports are clean. Dirt tends to build-up around top port.

TxGreaseMonkey

24. Fuel Injector Replacement

1. Depressurize fuel system. On many Hondas, it's as simple as removing the gas cap. Other cars require removing the connector to the inertia switch in the trunk, or pulling the under-hood fuse to the fuel pump, starting the car, and waiting for the engine to stumble.

2. Disconnect negative battery cable.

3. Remove connectors from injectors.

4. Disconnect vacuum hose and fuel return hose from fuel pressure regulator. Place a rag over hoses, before disconnecting.

5. Disconnect fuel hose from fuel rail.

6. Loosen retainer nuts on fuel rail and harness holder.

7. Disconnect fuel rail.

8. Remove injectors from intake manifold.

9. Slide new cushion rings onto fuel injectors.

10. Coat new O-rings with clean engine oil and place on injectors.

11. Insert fuel injectors into fuel rail first.

12. Coat new seal rings with clean engine oil and press into intake manifold.

13. Install fuel injectors and fuel rail assembly into manifold. NOTE: To prevent damaging O-rings, install fuel injectors in fuel rail first, then install them in the intake manifold.

14. Align center line on connector with mark on fuel rail, if applicable.

15. Install and tighten retainer nuts.

16. Connect fuel hose to fuel rail with new washers.

17. Connect vacuum hose and fuel return hose to fuel pressure regulator.

18. Install connectors on injectors.

19. Turn ignition switch to ON, but do not operate the starter. After fuel pump runs for approximately two seconds, the fuel pressure in the fuel line rises. Repeat this two to three times, then check for fuel leaks.

TxGreaseMonkey

2. Rebulding 2-Cycle Carburetors

In an attempt to keep everything a little weird and funky, I thought I'd share my experience rebuilding a 2-cycle carburetor.

I stayed up late last night rebuilding a Walbro carburetor to my Weedeater Trimmer ($78, Home Depot). I suspected the Pump Diaphram was weakening and causing the engine to die. I bought a common Walbro K10WAT rebuilding kit ($7.45, eBay). After replacing everything, the trimmer started the first time, ran well, but would not restart afterwards. I also replaced all hoses with yellow Tygon Fuel and Oil Line (3/32" I.D. x 3/16" O.D.) and cleaned the fuel pickup, air filter, and exhaust port.

After tearing the carburetor apart again, the problem was the Micro Screen, located beneath the Pump Diaphram--it became clogged, even though I could not see it. Previously, I had tried cleaning the screen with brake cleaner spray. After I picked out and pressed in a new screen, everything ran great. Hopefully, my experience will benefit someone else.

Dealers say these trimmers should last 2 to 3 years. Because of the long growing season in Texas, my trimmer gets used a lot--it's 14 years old and I expect it to last many more. I use Amsoil Saber Professional Synthetic 2-Cycle Oil, rated API TC, mixed 100:1.

TxGreaseMonkey

20. Reading a Tire's Manufacturing Date

Studies show that tires more than 6 years old can be very dangerous. Ensure that your "new" tires were recently manufactured, not sitting in the warehouse for years. Here's how to read the code on tires; for example, (3307) means the tire was manufactured in the 33rd week of 2007. The tire's manufacturing date is imbeded in the last code on the tire.

TxGreaseMonkey

12. Eliminating Air Conditioning System Odors

Air conditioner odors can be unpleasant and unhealthy. Here's an inexpensive approach to get rid of the problem. Mix a solution of liquid dish soap and bleach in a spray bottle. Attach a suitable hose and pump the solution in the evaporator coil drain tube, which is located on the passenger's side of the firewall. Be sure to insert the hose all the way in. Afterwards, flush everything out with clean water.

TxGreaseMonkey

14. Fuel System Troubleshooting

This is a two-part problem: 1) Determine if the fuel pump works, and 2) Determine why the PGM-FI Main Relay doesn't work properly.

If you don’t hear the fuel pump run, when the ignition switch is turned to ON (Position II):

Problem 1: Determine if the fuel pump works.

1. Disconnect the main relay from the main relay connector. Jump main relay connector Terminals 5 and 7, turn the ignition switch to ON, and listen for the fuel pump in the gas tank. If you can hear the fuel pump run, which is usually the case, it is likely good and you should proceed to Problem 2. If it doesn’t run, go to Step 2.

2. Turn the ignition switch ON. Measure voltage between main relay connector Terminal 5 and ground. If there’s not battery voltage, test/replace the ACG (ALT) (S) (15 A) fuse in the under dash fuse/relay box. If necessary, repair an open in the wiring between the main relay and the ACG (ALT) (S) fuse. Verify that you now have battery voltage to Terminal 5. If the fuel pump still doesn’t run, however, go to Step 3.

3. Check for continuity between main relay connector Terminal 7 and the fuel pump. If necessary, repair an open in the wiring. If the fuel pump still doesn’t run, go to Step 4.

4. Check fuel pump. Even though it's certainly possible, I have never seen a Honda fuel pump fail. They are very reliable. Clean connections and thoroughly test pump motor, prior to replacement. Before going any further, all efforts must be focused on getting the fuel pump to run (i.e., solve Problem 1 first), when main relay connector Terminals 5 and 7 are jumped and the ignition switch is turned to ON. If the main relay and fuel pump still don’t work properly together, however, go to Problem 2.

Problem 2: Determine why the PGM-FI Main Relay doesn’t work properly.

5. Check for continuity between main relay connector Terminal 2 and body ground, with the ignition switch OFF. If there’s no continuity, clean the main ECM ground, which is usually located on the thermostat housing. Look for 3 wires going to a brass connector. Remove the 10 mm bolt, clean with No. 240 abrasive cloth, and apply dielectric grease. If necessary, repair an open in the wiring between the main relay and the main ECM ground. If there’s continuity, go to Step 6.

6. Measure voltage between main relay connector Terminal 1 and ground. If there is not battery voltage, test/replace the ECM fuse (15 A) in the under hood fuse/relay box. If necessary, repair an open in the wiring between the main relay and the ECM fuse. If there is battery voltage, go to Step 7.

7. Turn the ignition switch to START. With manual transmissions, depress the clutch pedal. With automatic transmissions, the gear selector must be in Neutral or Park. Measure voltage between main relay connector Terminal 6 and ground. If there’s not battery voltage, test/replace the STARTER SIGNAL (7.5 A) fuse in the under-dash fuse/relay box. If necessary, repair an open in the wire between the main relay and the STARTER SIGNAL fuse. Should the main relay and fuel pump still not work properly, go to Step 8.

8. Perform the K-Test on the ECM. Remove the MAP Sensor connector and turn the ignition switch ON (not start). 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 ECM controls grounding to main relay Terminal 8, which affects when the second relay inside the main relay opens and closes. If the ECM cannot control grounding to the second relay, the fuel pump will not run. The only alternative is to replace the ECM.

SUMMARY OF MAIN RELAY PROBLEM AREAS:

Terminal 1--Test ECM fuse in under hood fuse box.
Terminal 2--Clean main ECM ground on thermostat housing.
Terminal 5--Test ACG (ALT) (S) fuse in under dash fuse box.
Terminal 6--Test STARTER SIGNAL fuse in under dash fuse box.
Terminal 7--Test continuity to fuel pump.
Terminal 8--Test ECM (K-Test).

Many hours of research, thought, and experience went into designing this easily understood approach to troubleshooting one of Honda's most complex systems. I consider this the most thorough coverage of this subject anywhere--it doesn't get any easier or better than this. I'm proud of this work and hope it blesses many people.

TxGreaseMonkey

13. Importance of Changing Automatic Transmission Filter

The link below highlights the importance of dropping and cleaning the transmission pan, changing the transmission filter (each time), and refilling with automatic transmission fluid every 30,000 miles:

http://www.amsoil.com/lit/filter_man_council01.pdf

TxGreaseMonkey

7. Antifreeze: Automaker Approved Chemistry

Using the wrong antifreeze in your vehicle can be a costly mistake. No "one size fits all" antifreeze is approved for use in all vehicles. Play it safe and consult your Owner's Manual. The link below may help:

http://www.valvoline.com/pdf/Zerex_CoolantChart.pdf

Use a 50/50 mixture of approved antifreeze and distilled water, in order to minimize deposit buildup (cheaper and better). Otherwise, buy prediluted ready-to-use coolant, which is a 50/50 mixture of antifreeze and demineralized water (more expensive, but convenient).