97 Honda Civic HX 207k miles stock.

Ok I'm at my wit's end with my civic, my problem started 3 weeks ago, I was on my way to work 20min trip, going like 65 or so and my car would "stall" ever so briefly while at speed, I would hear my main relay click off/on, off/on, off/on every so often for only about a second, then the car would start back up and keep running. when this happens it was just like the car lost all power to the relay/fuel pump is the only way I could describe this. I removed my Main relay, did a good inspection of it, everything looked fine, put it back in. On my way home from work the car just straight up stalled and wouldn't restart, however this time the main relay wouldn't click back on period, and the check engine light stayed on and wouldn't go off. Needless to say I got towed home.

My next day off, I start checking things out, and talking to some friends and local mechanics/auto parts stores and all the info I could fine online. After many discussions I had many people telling me my problem was my Ignition control module and/or my coil.....so I replace both (my car was a late production and doesn't have the standard 97 parts so everything is like 50 bucks more per part which sucks badly).....replace the coil/and ICM. Problem isn't fixed, CEL is still staying on, main relay still won't click on. figure what the hell lets go to autozone rent a OBD2 and see what codes I'm getting, hook it up, keep's coming back with an commucation error, I look thru the instructions real quick, realized I needed to change a setting on it for the car being unable to run...when I did this, I hear a series a clicks from a few different relays including the main, my CEL finally goes off, and the car starts up but still is stalling out. Finally stalls completely again and the CEL is back on.The OBD says its passes and had no error codes reported. So I unhook the OBD2 and take it back get my deposit back. Friend tells me to check the voltage running from my computer to my map sensor cause maybe my computer is going out, when I unplug my MAP sensor to test it, guess what my CEL went out. The voltage was perfect like it should have been so I plug it back in, and the car starts right up....and runs just fine, let it idle for 20min's w/o a problem. Drove the car around for 30mins w/o a problem one so I figure my problem has been fixed.

Take the car to work for two days in a row w/o problem both are hot *** texas summer days, on the third day it dies pulling into work, I leave it at my store till payday so I can buy a new main relay cause I figure that's gotta be the problem at this point.

So now I got a new main relay in, drive the car home. Drove like it was new again almost, no hesitation, no stalling, no cutting in and out, this was at night too. Next day heading to a friends house, car starts acting like the main relay is cutting off/on stalling the car again, however way way way less frequently, and it never actually "shut off" either this time, i didn't chance it, brought it back home got the other car....

So this is the point where I am now, looking for any advice I can get, i'm a broke college kid so taking my car in somewhere is kinda outta the question for me currently. My car isn't ragged out, it only takes me to work and back and that's all 44miles a day round trip. I've kept up on oil/filters/tires/CV axles/joints/plugs/wires/and other wear n tear stuff.

I've replaced the ICM, Coil, and main relay now.

The car does NOT smell likes its running rich, and I've only noticed a very small decrease in gas mileage over the past couple months, figured that was just due to high mileage though.

 

Sounds like a major power or ground problem, or remotely possibly a bad ECU. Definitely not the coil or ICM. Check the ECU ground wires on the thermostat housing, these are essential for the whole system. The whole system "clicking off" like you turned the key off could be a bad ignition switch. Make note of what the dash does when that happens. Does the speedometer instantly drop to zero even though the car is still moving? When you are trying to start it and it won't, pull up the brake handle and watch the BRAKE warning light. It should stay on steady both with the key on and while cranking. When the CEL stays on with the key on engine not started it means the ECU is not running.

The 96 and later main relays have few problems, but any time you open one up go ahead and resolder it to be sure.

 

Definitely check the important G101 ground wire attached to the thermostat housing. Ensure that it is both clean and tight. Also check fuses 44, 31, and 13 to see if they are loose or damaged.

I don't think the problem is the ignition switch because it would not throw a solid CEL.

 

Ground is clean and tight, no corrosion on it. All fuses fit tight, visual inspection and used a multimeter. The CEL is no longer staying on since I ran the OBD scanner on, when I changed the setting in it, it cleared the CEL and this was no the code clear option it was just the option to set it for a car that was "Not running."

I can go outside and crank the car and it will run, just fine but its still randomly clicking at the main relay just like the click you hear when you turn your key to the "On 2" position, before when this happened while I was driving I never noticed the speedO drop to zero, just the CEL would click on for about a millisecond along with the light to the right of it which I can't honestly tell which one it is cause its so brief its on. I did notice the car doesn't seem to completely stall anymore as well, I just hear the relay click, the CEL comes on for about a millisecond, the car loses power for about half a second then the RPM is kicked up, then it settles down. Sometimes it will do this 2-3 times in 10seconds, other times it might take 10mins to do it a single time. With the texas heat being what it currently is, I won't drive it cause I don't want to get stranded waiting for a ride/tow to get me. I did notice while messing around in the drive way the relay gets almost so hot you can't touch it, this doesn't seem right to me but I have zero experience with them. I've also had two people tell me it could be my MAP sensor and a few folks say the ignition switch, both are original, but I didn't think a MAP sensor would create a problem like this, my understanding of them would just have your car running like junk, but I could be wrong car's aren't my thing anymore.

Any input would be greatly appreciated

 

replace that ""hot"" relay its bad