I have a 1987 Honda Civic sedan with a D15A2 engine and a 5-speed manual transmission. It is the 12V CVCC design. It has a computer controlled carburetor, but still has idle screw. 293,000 miles on it. It has a mechanical fuel pump under the hood.
I just recently purchased this car for $325. It had a blown head gasket (between cylinders 2 & 3, typical for these cars) and I replaced it with the Fel Pro reinforced gasket and torqued the head to specs 49 ft-lbs. It has new coolant, new oil, and new transmission fluid.
The car will not idle below 1300rpms, when it is warm. When it is cold, I have to turn the idle up even higher otherwise it'll die when I take my foot off the throttle. I also notice that when I turn accessories on (the fan, the lights, the radio, even pumping the brakes) the idle will go below what I have it set at. If I use too many of these accessories at once my idle will drop and it will lope as it gradually gets lower and lower until it finally stumbles and the car dies.
There is a vacuum line that is disconnected and plugged. When I connect it to where is supposed to go it pulls the idle down so that the idle lopes a lot. It'll pulse so that it'll be idling at 1300rpms, then the idle drops and its about to die, then the vaccum will stop and it'll idle at 1300rpms again, and then it'll repeat itself. I have no idea what this device is for but I'm assuming its not supposed to do that (which is why the previous owner has the vacuum line unhooked). Could this thing have something to do with making it idle correctly below 1300rpms? I think it may be called the dashpot or something? I'll post pics when I get the digital camera back from my sister later today.
The spark plugs look in good condition. I have sprayed carb cleaner down in the carb before. I've checked the ignition timing and it seems to be within factory specs. The car should idle at 750rpm according to the underhood sticker.
What could be causing this?
My father suggested that the idle jets could be gummed up too much.
I thought that it could possibly be the fuel filters (it has one before and after the pump) because fuel filters are generally the forgotten filter on cars and it could very well be the original filter which means it has nearly 300,000 miles on it. If the filters were clogged up too much the fuel pump (which is driven by the engine so at lower engine speeds its not pumping as hard) might not have enough power to pull/push the fuel through the clogged filters but it does have enough power at higher rpms. So basically a clogged filter and the engine is starved for fuel.
I'm not experienced with carburetors and this thing has a ton of vacuum lines going everywhere on it so I'm at a loss.
I'd GREATLY appreciate any help from someone with experience with these Honda Civics. If they wanted to make it pass emissions so bad I wish they would've just went with fuel injection instead of a computer carburetor with 1001 vacuum lines on it. :\
I have the same engine/carb as you and I replaced my head gasket last summer.
You can easily check to see if the carb has enough gas by kneeling beside the front drivers wheel and looking just over the top of the strut at the drivers side of the carb. You might need to push a hose or two out of the way, but there is an "H" shaped sight glass built in to the side of the carb that will show you the level of fuel in the bowl. This will verify that the filters aren't an issue and you can see if it might be flooding out due to a bad float valve (this will cause bad idle too).
The dashpot that is disconnected does help to control idle speed. It should have a "hooded" adjustment screw that you can reach with a long screwdriver. Hook the vacuum line back up to it and turn the screw it a ways and try to start the car.
The only electric component on the carb (besides the choke warmer) is an idle cut off valve at the back of the carb. It should have voltage when the ignition is one. If the wire to this was unplugged then the car couldn't idle at all (it is designed to prevent "run on" or "dieseling" when a hot engine is shut down).
You might check the EGR valve to see that it isn't stuck open.
Did you unhook all of the vacuum hoses when you replaced the head gasket? or did you just scoot the intake backwards out of the way?
If the above items check out OK, then it might be a vacuum leak in one of those 101 hoses. Oh- and typically at least on of the two vacuum advance diaphragms on the distributor will go bad and this will create a vacuum leak. You can check each one with a vacuum pump.
When you checked the timing, you did remove/plug both of those hoses right? Otherwise the timing will be too far retarded. It should be 20 degree BTDC without any of the vacuum advance hoses hooked up.
You might just advance the dist a little and see if it will idle better. It will only take a minute or two to see if that helps.
On our engines, mixture is controlled by a "regulated" intake manifold vacuum leak. One of those black boxes on the firewall has the control valves in it. I have been tinkering with my system to lean it out a little more.
I'm glad you found this thread, I actually had you in mind when I was typing it since your the only other person I've found on GasSavers.org with a car like mine.
I'll try that stuff out as soon as possible, hopefully tomorrow. Right now I'm replacing the oxygen sensor. The wire accidentally got ripped out of it when I was taking the exhaust manifold cover off while changing the head gasket. I'm putting on a 4-wire sensor off of a 1994 Pontiac Trans Sport minivan. That should be a quick wire-up tomorrow and then I'll try all your suggestions.
The idle cut-off valve and the H-shaped glass sound like good things to start with, I had no idea about those so thanks for the tip.
The dashpot, I've had it plugged in before and tried turning the idle up but perhaps I was being too cautious and didn't turn the screw far enough so I'll try that again.
As for the timing, I did have the vacuum hoses unplugged from the advance mechanism BUT I did not have then blocked off. So I can check that again too.
I'll keep posting as I try this stuff and see if it helps any.
Last week, I bought a 1.3 CVCC engine at a pull a part yard to swap into my civic (even though my 1.5 CVCC is running great). The 1984 CRX with 1.3 CVCC was rated for 55+mpg on the highway. I will take me a few weeks to open the engine up and have the valves ground etc, but I am shooting for 50mpg on the highway, even though my aerodynamics are much worse than the CRX.
Once you get it idling/running right, I can tell you how to modify the mixture control system to lean it out further.
I just got a manual from the library with the wiring diagrams for 1987 hondas and the 87 CRX HF has a little computer control unit that controls the alternator charging (I'm guessing that it only applies power to the alternator field when the batt voltage gets low- so it only charges part of the time). This is one of the differences between the 87 HF and our cars (there is no such unit on our cars- they are always running the alternator- always topping off the battery,a nd wasting some gas).
I'm jealous, I've always wanted the HF model. I was hoping I could eventually convert my to the HF as much as possible by putting in a HF transmission, and HF carb, and now something to control the alternator charging I didn't even know about that. Good luck with that project should be very rewarding when its finished.
Anyway, I turned the idle up to around 3000rpm with the dashpot unplugged and then I plugged it in and it the idle dropped to 1000rpm. If I turn on several accessories it'll drop to around 800rpm. I can't seem to get it below 1000rpm even if I turn the idle screw in more, but its better than the 1300 before.
I checked the ignition timing again since the engine was much closer to the specified idle speed and I blocked off the vacuum hoses this time. It may have been a little too far retarded like you said, but it should be close to factory specs now, a little advanced though.
I added the 4-wire oxygen sensor in but I can't seem to get the right reading on my DMM maybe I hooked up the wrong wires or maybe that sensor was bad as well, but now when I'm accelerating in gear there is a loud tapping sound. I'm not sure if this is what they call "knock" as I've never had the chance to hear an engine knock and make note of the sound.
I'll start checking the other stuff pretty soon and see if I can drop the idle down an extra 300rpm.
Hmm...now that its cooled off it wont idle at all. I guess it'll idle at 1000rpm when its warm but when its cold I have to keep my foot on the gas otherwise it stumbles and dies again. I found the little H-window. I'll clean it off a bit and see how much fuel I have. Where should the fuel level be in this window? How will I know if its too much and its flooding out?
The gas level should be in the center part of the H. There is a screw on top of the carb to easily adjust the fuel level in the bowl.
A Q tip works well for cleaning the sight glass off.
A loud tapping sound under acceleration- hmm- if you had advanced the timing I would say it could be spark knock.
Just out of curiosity- why did you switch to a 4 wire sensor? Just to help it heat up faster? I'm not sure which wire you would plug in to the O2 sensor spot on the harness. There should be two heater wires that have continuity between them- maybe you will have to ground one of the 2 left over wires and the last will plug into the harness.
My car seemed to run the same with or without the oxygen sensor plugged in. I've had it plugged in for the last 1.5 years.
My car can't adjust its idle well for load either (it idles a little lower with the lights or heater fan on).
No cold idle- check to see that the choke plate is closing when cold like it should.
The engine that I got isn't an HF engine, but the 87 civic with the 1.3 was rated for 39 mpg on the highway, while the 87 with the 1.5 is just rated at 32 on the highway so I figure it should help a substantial amount.
I decided to try a 4-wire oxygen sensor mainly because of the heater in it. It is also grounded through a wire instead of the exhaust manifold so they are supposed to be a bit more accurate, but on a carbureted engine I doubt it'll make any substantial difference, I may just pay $18 and put in a new OE type sensor.
I'm assuming you mean the gold screw at the top middle of the carb when you take off the air cleaner, so I'll adjust that tomorrow and keep an eye on that little window to see where the fuel level is. It may be flooding out as you suggested because even when it was idling cold if i tried to hold the choke closed manually it would end up dying faster. The choke closes but it looks a little loose and might be opening too soon, I'll have to check it out.
The 1.3L should still be very nice though its not HF. If your already getting 42mpg out of your Civic it should be plenty capable of 50mpg when you switch that engine in. My engine looked in great condition when I had the head off mine, I'd assume those 1.3L's were just as durable so it should last you a long time once you get it put in.
I was just playing around with my idle. I found the adjusting screw you were talking about, the one by the fuel line. I got the idle down to around 750rpm when its warmed up. I'll have to see how it acts later when its cooled off. But it still likes to get very close to dying when I have my accessories on. When the accessories are on and I pump the brakes it does die sometimes.
I was thinking though, however owned the car before has the cooling fan wired so its always on. From what I've heard these fans like to use a lot of power, so I'm sure thats affecting my idle if the in car accessories bring the idle down. I'll have to see if I can wire it back up to the sensor so its only on when it needs to be, or maybe I can just wire in a toggle switch I'm not sure yet.
Also, since the muffler was rusted off when I bought the car, and I haven't replaced it yet, could this be affecting the idle? From what I understand, cars do not need backpressure, they only need exhaust velocity. However, supposedly backpressure helps keep the power down in lower RPMs while no backpressure keeps the power in high RPMs. These engines aren't that powerful and I'm not an expert on carbs, since this is my first carbed car, but wouldn't no backpressure on this car affect it worse than a fuel injected vehicle? Fuel injection can simply inject more fuel, but carbs are limited by the size of their jets.
So...I think my last problems may be that the cooling fan is always on, no backpressure makes the powerband too high / not enough low RPM power, and no backpressure is allowing too much air through and its possible running a tad too lean. Think this may be the last of my problems?
I had a few questions about your Civic. Do you ever have any problems with the 195 degree thermostat? I had a 195 one in, but I put in a 180 degree one because I was afraid of blowing a head gasket again. And your cruise control, Audiovox CS100 Cruise control, I'd LOVE to put cruise control in mine. I've gotten too used to it and now I can't keep a steady speed with my foot and I'm sure thats affecting my mileage. I've done a lot of searching but I can't seem to find the Audiovox CS100 Cruise control anywhere, maybe its a typo and you actually have the Audiovox CCS100? Thats the closest thing I can find on Google or the company website. If not, where did you get your CS100?
Thanks again for all the help, you've told me more useful info than my Haynes Repair Manual ever has.