Hi all. Having a problem with my 95 Civic EX. Idles beautifully when it starts, but cuts out when you step on the gas, especially if you step on it hard. If you step softly on the gas you can slowly manage to get around to a quick location, but when the car heats up it is almost impossible to drive as it stalls constantly and barely starts up again.

Took it to the mechanic and he told me he couldn't figure what was wrong with the car. Said it's PROBABLY the distributor... but wanted to charge a fortune to fix. I had recently replaced the ignition coil, cap and rotor, so I took the car home, bought a new igniter and installed it. Brand new distributor now, didn't help at all. No check engine light, and the light stays solid when you jump the computer wire, so no codes are present. Since there are no codes I think the sensors are fine, tested TPS but not MAP. Spark plugs are firing, they're brand new. Tested fuel filter and it is working fine. I don't know what else to do!

Please help if you can.

Do you have a method to check time? I just recently ran across one of these that was way out of time and acting very similar.

I would focus on the main relay. It appears to have classic elements of main relay failure; i.e. heats up, solder joints expand, intermittent electrical flows affect power to fuel injectors, second relay, and fuel pump. I recommend replacement every 120,000 miles or 10 years, whichever comes first. Main relays are a very problematic component. My experience has been that Honda owners have more problems with main relays than any other component.

Here are some basic diagnostic tests to run:

1. When you turn the ignition switch to ON (not START), 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); 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.

Before touching the main relay, you should rule out a problem with your ECM. Therefore, run the K-Test: Remove the MAP Sensor connector and turn the ignition switch to ON (not start). Using a multi-meter, 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.

If the ECM and main relay does not fix the problem, I would check the MAP sensor. This is the key sensor on many older model Hondas and controls timing and fuel, under constantly changing conditions. This is a very expensive transducer, so rule out most other components before replacing.

Thanks for the responses.

Will check timing tomorrow. As far as the main relay goes, when you start the car the CEL goes on for the 2 seconds and you can hear the fuel pump and the click when it turns off. I could be wrong, but I thought main relay faults are usually associated with hot days, and it's freezing outside... but I will test that out as well just in case. In the meantime, any more suggestions?

In the majority of cases, main relay problems surface on hot, summer days. However, main relays fail other times as well. I've seen some particularly poor soldering on main relays, where joints fracture badly. Many times joints don't have nearly the proper amount of solder on them. Newer relays appear to be more poorly made than older ones. Car vibration eventually takes its toll on these joints and intermittent starting and running problems develop. This can happen anytime of the year. Remember, much of the heat affecting a relay is self-induced. There are two relays (coils) in the main relay, both of which are always on and generating heat when the car is running. Both relays are soldered to the circuit board and the heat generated is trapped by the surrounding plastic cover and conducted into the board. It would probably be a good idea to drill small ventilation holes in the cover. Next time I pull mine out, I plan to do this.

It's important to rule out the ECM first, because main relay terminal 8 is a computer-controlled grounding terminal. Problems with the ECM significantly affect how the main relay operates. Therefore, problems that appear to be main relay-related are sometimes caused by failing ECMs.

Part of me still suspects the fuel filter, even though you said you tested it. The fuel rail must be pressurized, in order for the injectors to fire. Fuel filters should be replaced every 60,000 or 48 months, whichever comes first.