Not getting impressive fuel economy with the Civic
 

Hi guys,

I have been experiencing less-than-stellar fuel economy in my Civic VX as of late.

When I first bought it in Feb of 06, I used to get at least 38-40; now I'm lucky to get even 32mpg.

Here's what I've done so far since owning it:

Spark plugs
Spark plug wires
O2 Sensor
Timing belt and water pump
A/C and alternator belt
Fuel filter
Distributor cap and rotor
Proper tire pressure on all 4 tires
Oil pan gasket and valve cover gasket replacement
Adjusted valves
New EGR valve
Adjusted timing to proper setting
Cleaned IACV and FITV
New catalyctic converter

One thing I haven't done yet is fuel system cleaning.

What the hell gives? It barely lasts me 300 miles on a full tank.

Also, the car is bone stock, with the original D15Z1 intact.

Thanks.

Is it running rough? Fast idle? Symptoms? Are you driving differently? I can only suggest some new/used 190cc VX injectors like you thought or maybe timing....

Did the mileage get worse after any of the service was done?

Good Luck!
Kent

yea we need more symptoms. not just the problem. it could be the new cat.... but with such a drop, there has to be more than one problem

Haven't had any symptoms, other than usual V-TEC-e kick at 2100rpm's or so.

I usually drive it a bit hard just to keep up with traffic, but I even drove it normal a couple of times and it has yielded no improvement in fuel economy.

Would fuel system cleaning at a shop help? I'm frustrated because I bought this car with the assumption that it would net me at 40mpg or higher.

I'd jack the car up and see if you have any brake drag.

Brake drag? Elaborate.

its where your front calipers and or wheel cylynders act like your constantly pressing the brake as you drive. go for maybe a 5 minute drive at highway speeds (or close to it) without touching your brakes. pull off the highway on a side street or somehting, get out and touch the rim itself and lugnuts (take off the hubcaps prior) if they burn you that wheels brakes are dragging. if its somewhat warm its normal, but if its liek touching a frying pan its dragging.

it can becaused by several things, siezed calipers (rusted) or if you hit anyhting to cause a crease in a brake line it will allow you to push fluid thru the crease but will have a hard time comming back thru to release that brake. also deteriating rubber caliper brake lines can do this.

ooo maybe if you hit something it couldve whacked out your alignment...

anyway what kind of driving do you do?

My guess is a bad cylinder. I experienced a very loud detonation event going up hill at 75 mph with the VX overloaded with some of my stuff when I moved to Michigan (I know, that was really dumb!!). It was never the same after. Its mpg dropped from 45 to 35 once this happened. You might want to do a compression test on all 4 cylinders.

^^^ you may have burnt a vale or somehting^^^^^^

but yea a compression check is like a MRI for us. it tells ups whats going on internally in the engine with a very easy/simple test.

Well I use the car for my work (I do food delivery for an Italian restaurant) so it's a lot of stop and go driving. My driving style during work is sometimes aggressive (which I can understand), and sometimes even relaxed.

Outside of work, I am very easy on the vehicle but the fuel economy isn't much of a difference.

And as for a compression test, good point. I hope I have proper compression, but who knows?

Thanks for the suggestions.

who did the timing belt? when I had mine changed they screwed it up and had it off by one notch, after that I could really tell when the v-tec was kicking in (it should be smooth and hardly noticable) my mileage droped, and power droped, normaly the v-tec-e engine has alot of power.

A shop that knows Hondas inside and out.

man it would help if you had a gaslog so you could see exactly where it fell on its face...

That doesn't alwas meen it was done right, on most Honda's you line the marks on the cam sprocket up with the top of the head, but if you read the shop manual you'll notice that the VX is the exception, and that there are little arrow marks on the head that you line the sprocket up with insted, and over confident mecanic might not notice this set of marks and line the cam sprocket up with the top of the head insted, and this is wrong, of course you can check this your self by taking the cover off the cam gear, and lining up the crank shaft pully with the Top Dead Center mark, if everything is correct then the TDC mark will line up at the same time that cam gear marks line up with the arrow mark on the head.

the other option is to take it to the honda dealer, and ask them to take it for a test drive to figure out what is wrong, after all you said that you could tell when the vtec was kicking in, and this shouldn't be the case, other then a very very slight increase in power.

I used to keep track of receipts by putting the amount of miles the fuel tank filled up, but my dad threw them away by mistake :(

So what readings should I expect in a properly maintained VX?

160psi on 1, 155psi on 2, 155psi on 3, and 135psi on 4

Got my compression test results in.

^^^^ that number 4 is a bit low....did you do it twice to verify numbers, or run a wet test?

Ran it twice to verify the readings and they stayed consistent.

Wet test? Do you mean leak-down test? If so, no I didn't do that. Should I do that to better determine the issue at hand?

wet test/leak down test.....they are the same thing. Small amount of oil in the cylinder, then compression test. However, if you've got crappy compression in the first place, a wet test usually will show crappy compression again in that cylinder.

With one cylinder being low like that, it's time to start looking in other directions. Does your oil have a gas/oil smell?? Do you have a frothy/chocolate milk substance on the bottom of your fill cap (or on your rad. cap)?? Are you losing coolant at all?? Smoke from the exhaust?

^^^ Trying to help you diagnose a little further before you decide to tear apart the motor for valves/head gasket/piston rings....

With the compression numbers you've got, one way or another, you have a imbalance and a problem with the number 4 cylinder. If you squirt some oil into the #4 cylinder and retest the compression, it may show you whether the problem is in the valves, head gasket, or rings. It also may not, since if you have a bad valve it isn't going to seal, no matter what you do.

Have you had any problem or problems with overheating, running low on water/antifreeze?

Their are several possibilities. First, the head gasket could be shot. This is where Raccoonjoe is asking about the oil, radiator cap and exhaust. It may be something you had happen, or it could be something which happened 50,000 miles back and it's just showing up now. If it's the head gasket, you may be able to just get away with pulling the head, cleaning everything up and putting it all back together.

But, it's a gamble. If the head is flat and the block is flat, then the gamble might pay off.

Alternatively, it might be a burned valve, in which case you would need to get a valve job and a head milling to square it all up.

If it's rings, then you might be able to get away with putting in new rings, or you may need to either get a replacement engine, or have the engine rebuilt.

What does the spark plug from #4 look like? Is it more white and clean, like the other three plugs, or is it more black, oily, sludgy looking. If it's clean, then it's probably a valve or head gasket issue. If it's dirty, then it's probably rings and a rebuild.

If you do the head gasket, I would suggest you use a head gasket for a 92 Civic Si. The head gasket is all metal, instead of a fiber compound, so it reduces the liklihood of doing a replacement later on. If you do, you will still need to get a head set, to get all of the other gaskets which are correct for your car.

None since I have owned the car.

The oil doesn't have a gas smell as far as I know, and the coolant does not show to be milky one bit.

No smoke coming from the exhaust.


It was white and clean, showing normal wear.

maybe it just needs a good old dose of sea foam?

Well, I don't know what to think. Is their any possibility that the timing belt might have been replaced, off by one tooth. The car would still run, but it probably wouldn't seem to much get up and go, on the highway. I know it was done by a reputable shop, but I also know a reputable shop did the belt on the wagon I'm currently driving and somebody choked because they marked the pully on the crankshaft incorrectly. I had to find TDC on cylinder 1, by pulling the plug, putting it close and then sticking a piece of welding rod in the hole where the spark plug goes. Then I could turn over the crank and find TDC and it was definitively marked wrong by the mechanic who had replaced the belt.

You can check it without pulling the timing cover, by doing the same thing I did. Use a 17mm socket to turn the crankshaft over, to where it's near TDC on number 1 cylinder. You can pull the cover to the distributor and look at the rotor, if you wish. Pull the 1 spark plug, use a long piece of wire to put into the hole, then you can turn the crankshaft to where the wire is as high as it will go and the crankshaft will be at TDC. The spark plug rotor should be at the number 1 position. If it's off by about 1/4 inch, then the belt is off by a tooth.

I wouldn't do a head gasket replacement if you don't have to and if number 4 spark plug is like you described, it doesn't sound like the rings are bad.

Does it idle a little rough?

I'll give that a shot after the new cat was put in place.

Not at all. It idles very smoothly and stays stable.

I dunno if this has been addressed but have you switched gas stations lately? Different blends and the occasional crap tank can screw up mileage. Without engine problems the next place to look is alignment like suggested, specifically toe, which if is out of spec can eat tires as well. Just a thought. Mak

Hanging calipers (common problem in the fronts on the Hondas) can greatly impact the MPG numbers....might check those as well.
How was the test performed??? Those numbers are really low. I recently did a compression check on my VX motor with over 330K miles on it and got 200, 195, 198, 201 in cylinders 1-4 respectively.

The test was performed with a regular compression gauge but we did not disconnect the injectors so my guess is that it did not give the readings correctly.

Also, I noticed that my car has crap fuel economy with the A/C on at 230-260 miles on a normal fuel tank. It's ridiculous and it also does not drive well either. This occurred after I got the A/C recharged with R12.

I don't even know what to do anymore. Anyone in the Dallas/Fort Worth area want to lend their help to me? I can't figure out what the hell is wrong with this car.

I dont know if this has been mention but have you check the codes on the car. This might reveal something.

Hum I'm reading the thread and I'm asking myself, could it be your gas tank that actually leak. That is maybe why you aint getting good MPG, some of your gas just isnt consumed. It probably have many ways to find out, any advice on this guys?

Its just an option.

while I haven't had many leaky gas tanks in the past. Its something I would look into as well. You might also try running some marvel mystery oil through the engine and gas tank. While this wont fix the problem. It will ensure that things are clean.