I have a 98 civic si and I was getting 525km per 40 litres in the city. Over last year the fuel usage has gone up and I can't figure out why. Currently I am getting only about 450km per 40 litres in the city. My idle is fine and the engine does not seem to run roughly. I have noticed that around 2500 rpm I used to get a little surge of power and then again at 3100 rpm. As of the last while the surge of power at 2500 rpm is intermitent. I would suggest that the power seems to go away with the engine getting to running temperature however I have no proof just how it seems to me.
Anyone have any ideas of what might be the difficulty. I can tell you I have never replaced the PCV valve in the last 100,
000 km. Oh and the car currently has 190, 000 km on it.
Your cylinder compression may not be that good any more due to higher KM. - when the car warms up the oil viscosity goes down and because rings don't seal as good as when the car was new, there is power loss. Notice that good pickup just before the engine has completely warmed up.
The transmission is not as responsive as it used to be i.e. it switches to longer gears much sooner. So when you are going 60KM per hour in the 4th or 5th gear car feels lazy, and takes a while to upshift
I am not sure what you mean by intermittent. Sounds like ignition problem, maybe spark plug problem, contaminated fuel delivery system, injectors etc.
Does the engine run quietly or can you hear a lot of different mechanical noises?
The car is quiet except for a slight squeak when there is high humidity. What I mean by intermittent is that sometime when I am driving and I get to the 2500 rpm point I feel the little power surge and then sometimes I don't. Usually once the car is up to running temperature I find that surge of power is no longer there.
Any ideas? I can definitely look into the compression of each cylinder. What does everyone recommend for cleaning out fuel injection systems?
Compression tests are normally done when the engine is cold.
I did a test on my 98 civic (not a vtec) about a year ago, It had 250000kms on it. I got 190lbs of compression (+/- 4-6 lbs) on all cylinders. That is indeed the factory compression.
However, to get a better picture of the condition of the rings, how well they are sealed, as well as the valves and how well they are sealed, you need to do a leakdown test. Any competent honda mechanic should be able to help you with this. Then you can determine whether the problems you are having are valve related or cylinder/piston related.
Its a special tool that you plug into the spark plug hole on a cylinder with both valves closed. You then run compressed air through the tool, and it has a scale on it to tell if the level of leakage is acceptable (using Red-Yellow- Green criteria with an actually CFM rating to quantify the level of leakage). Also, you can tell where the leakage is occuring... if the air is leaking out of the intake, it means your intake valves are not seated properly. Out of the exhaust means exhaust valves. Anywhere else, probably means piston rings.
I did perform this test on my 93 Nissan Altima before I bought it from my brother. It leaked like a sieve through the intake, and the highest compression I could get out of any cylinder was about 85lbs. Kinda funny too, because the car actually seemed to be running quite well. I poured some Lucus Oil Upper cylinder cleaner into the fuel and drove the *(&^ out of it for about a week, and performed the same test. Now I have 160lb compression.
I have not performed the leakdown test on my civic as yet.
So you can try the Lucas Oil stuff (available at your local canadian tire or partsource, I assume you are in Canada if you are talking KMs), or try to find Chevron Techron fuel injector cleaner. Many people on this group have had great success with that product.
As far as fuel economy on my civic, normally I get about 450-500kms on 40L of fuel, mostly highway driving. Now have 282000kms on the motor. (its a 5 spd too). Keep in mind that mine is not vtec though, and that does make a difference (vtecs use more, generally speaking)
CarKB.comhttp://www.carkb.com/Uwe/Forums.aspx/honda-cars/200708/1 Thanks for the help folks. I am going to try the Lucas oil upper cylinder cleaner then do a oil change and put in a new PCV valve at the same time. Hope that fixes it and if it doesn't I will go with some of the other solutions. Such as checking the compression, etc.
On Aug 21, 3:49 pm, snipped-for-privacy@canoemail.com wrote:
Another relatively cheap thing to try if you're not already doing it is to switch from 5w20 to 0w30. It should be synthetic as rings seal / work better with synthetic due to the uniformity of synthetic molecules. I have a 2003 Accord (4 cyl) with just under 320,000Km and I use Amsoil 0w30 from 44,000Km. The engine is not maintained by any Honda / mechanics shops. The reason I switched from 5w20 to 0w30 is as follows and I will mention only the ones that may relate to your dissatisfaction. The main reaon to switch for me was cylinder assembly wear and tear. No matter how often you change your 5w20 honda motor oil, the viscosity at the optimum operating temperature is approximately 10% less than with 0w30. Since I am a little more heavier footed than most drivers it means that the internal cylinder moving parts could on occasion exceed the temperature range and enter in the "danger" zone for the 5w20 oil i.e. viscosity below 7 or even 6 (i.e. it is about 9 for 5w20 Honda oil at normal operating car condition i.e. hwy cruising between 90-100Km/hr). So the film becomes very thin until the water cools down the system, and eventually the viscosity increases back to 9. With 0w30 you have that extra viscosity capability at higher internal temperature. The end result is reduced engine wear when you are pushing the engine. I change the oil and filter every 32,000Km. Prior to oil change I drive the car with higher RPM on occasion (5-6k RPM) to burn carbon / film etc. if any is there (most likely nothing there). I then drain and fill it with 5w30 Autolab (cause it is cheap) fresh oil and run the engine for about ten minutes to wash it. I drain it and refil with synthetic. Does all this work well? I have done this on every car I've had since mid seventies on same oil (Amsoil. It doesn't have to be Amsoil - key here is synthetic). I am a bit surprised at the gas milage that you're getting. At 320,000Km Accord at 100Km/h I use between 5.8 and 5.9 l of gas per 100 kilomteres i.e. over 1000Km per tank (I only do hwy driving). If you eventually perform a compression test and fiind out that compression is low due to rings, you may try 0w40 synthetic. that has even better sealing properties at normal and higher engine working temperature. The negative effects of higher viscosity oil at normal operating temperature is higher fuel consumption.
To be honest, i have neglected the civic for the last 2 years at least. I will probably do some of the same as the OP, new PCV from Honda, check timing. I think I'll do a brake check too, perhaps one of them is binding and causing my mileage to drop...
Couple other things too, a bolt on my valve cover is busted, need to fix that. . its just sitting in there with some RTV sealant around it to prevent crap from getting in. Snapped bolt on distributor cap. Not sure if that will affect anything. Check all idler pulleys and accessories.
I was kinda hoping to wait to do this at the next Timing belt change (coming up next summer), but i have some time now, so it's proabbly a good idea.
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