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Old 08-01-2008, 09:31 PM   #1
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1994 Civic VX New owner disappointed!

Hi everyone, first time on this forum after reading so much about the Civic VX i found one and finally bought it for a good $2000 dollars. stock D15Z1 motor and tranny Theres a few problems.

I fulled the tank full, and drove 200 miles and filled it up for already 7.6 gallons!
thats only 26mpg!

I just got a full tune up on the car before the full tank of gas, plugs,seals,waterpump,timingbelt,flushed all fluids, coils, ignitor. cap, fuel filter, air filter, my mech sayed the o2 senor is fine and my egr is fine, and my plugs were fine. no chk engine lights at all.

The weird things i noticed about the car.
At a stop it idles funny. the car pulses and drops idle. its a steady pulses of 4 or 5 idle drop and runs like a normal car.. each time at a stop light. is that lean burn mode activated?

The tranny makes a low gowling noise when the car is in neutal and it goes away when its in gear.. inner shaft bearring?

The cars tires PSI was at 30 before i pumped it up to 40psi.. (44max) but i dont think a 10psi would have me drop about 20MPG!

The car was lowered by previous owner and is pretty low does that affect my mpg?

This car replaced my 93 integra which got 25mpg and it was spou to save me money. but now im very disappointed at my gas mileage. Im not a heavy foot and i do minor hypermileing but i should be able to speed freak on this car and still pull 35mpg min right? whats the deal? anyone know? i see everyone getting 40-55mpg .. =(

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Old 08-01-2008, 09:52 PM   #2
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I was getting ~30 mpg on mine when I got it. Had to get a new O2 sensor - fixed the problem, around 45mpg now. If you are certain that O2 is good, may be it's something else. From what I gathered O2 malfunctions could be hard to diagnose and do not always trigger CEL.

Also idle should stay steady at stop. I had a problem with mine - fixed by swapping IACV from a junk engine.


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Old 08-01-2008, 10:56 PM   #3
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The rough idle, pulsing and bad mileage are a dead givaway that the car is not running correctly. Lean burn is only active when the VSS (vehicle speed sensor) sends the ECU the minimum speed requirements and the MAP(manifold absolute pressure) sensor returns a low load report to the ECU. Additionally, the ECU requires a tac and temp signal and so on. Even if there are no codes diplayed, that doesn't mean that there isn't a fault in one of the monitored systems. OBD1 is limited on what is monitored, so you can have a problem with a non-monitored component like the cat.

Fedral law requires emission components in the US to be covered by warranty a minimum of 76,000 miles. Most O2 sensors have a life expectancy by their manufacturer of 30,000 to 50,000 miles and catalytic converters post 50,000 miles as the recommended change interval. I would imagine yours are past that point since most people live by if it ain't broke don't fix it. O2 sensor replacement is recommended on the same interval as spark plugs. This is rarely practiced, but it is by me. When your mechanic tested your LAF sensor did he use a scope? After all, it is the only way to tell if it is operating at a sample rate equal to the ECUs requirements. And no, if it is functoning, but too slowly, it won't throw a code, your car will just run bad.

I recently talked to a friend of mine who is a Honda Master Tech. He said it is common to need to rebearing the transmissions in these cars. They don't have a pilot shaft bearing at the rear of the crank to support the input shaft. Any side load or misalignment issues wreak havoc on the input shaft bearings. It is possible to have increased drag from a bad transmission but not common.

Lowering would probably improve mileage as long as there isn't some strange problem due to misalignment.

You should be getting way better mileage than that. I've never experienced less than 45 mpg in my VXs even driving like a speed freak.
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Old 08-02-2008, 04:14 AM   #4
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A couple of VX owners have had leaking fuel tanks. Maybe you do too.

Don't drive it for a few days and see if the fuel gauge level drops. Seems to me to be the most likely cause for a severe drop in fuel economy.

But, your engine could also have a cylinder with bad compression or high blowby due to piston ring malfunction. That should trigger the LAF sensor but not always will. Oil on the spark plug is the key sign of this problem - I know because I overloaded my first VX with too much stuff when I moved from Illinois to Michigan and experienced irregular combustion and piston/ring damage as a result. My mpg was never the same afterward - only about 34 mpg instead of the 45 to 48 it usually had.

Don't despair - a good mechanic will find out why the mpg is so lousy and you will soon enjoy the mpg that makes early 90's Honda's and especially the VX a pleasure to own. I bought my first VX brand new in May 1992. I was amazed by the EPA mileage ratings at that time and still am.
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Old 08-02-2008, 06:32 AM   #5
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Originally Posted by soletek View Post
I recently talked to a friend of mine who is a Honda Master Tech. He said it is common to need to rebearing the transmissions in these cars. They don't have a pilot shaft bearing at the rear of the crank to support the input shaft. Any side load or misalignment issues wreak havoc on the input shaft bearings. It is possible to have increased drag from a bad transmission but not common.

I confused about your statement saying these cars don't have a pilot bearing? Ever one I have taken apart has a pilot bearing in the center of the flywheel supporting the input shaft...I just put a new clutch in mine and replaced the pilot bearing...It is common for these transmissions to have the input saft bearing go...I actually think I am going to have to replace mine soon but I'm just unclear why someone would say they don't have a pilot bearing?

#12 is the pilot bearing this is for a 95 VX
MPG Noob

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Old 08-02-2008, 09:32 AM   #6
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Clarifying Pilot Bearing Issue

All Honda clutch kits I've seen come with a pilot bearing or bushing. It doesn't mean all transmissions use them. Especially in the case of Hondas. I have three Honda transmissions sitting on the floor in my shop. I also have two in cars I've restored. None of them have a stub on the front of the input shaft which would insert in a pilot shaft bearing hole. You are correct in thinking some of the transmissions do have a pilot shaft bearing, but definitely not all of them. If you would like to confirm this, you need to contact a Honda dealership directly and talk to one of their Master Technicians or knowledgeable Parts Person. You will find my information to be true. You are probably correct in that I was incorrect to assume that his transmission happens to be one without a pilot shaft bearing. I don't know the mileage on this particular vehicle, but usuallly the ones at this age that make input shaft bearing noises are the ones that don't have the pilot shaft bushing.

Since I seem to have upset the masses, I went on an information quest to find which models use transmissions without the pilot shaft support. I have found, so far, that model classification didn't seem to make a difference and each model, for some reason, may or may not have come with the pilot shaft bushing. The response I was given was that, "If it is one of the tranny's that doesn't have the provision, we don't put it in." I have yet to confirm the next statement about the side load: "Transmissions that came without the pilot shaft bushing snout also came with a flywheel that had a weight cast on the opposite side of the clutch surface for balancing to eliminate side loading." I am mainly quoting the Master Tech to whom I spoke regarding the last statement. I, also, have two earlier transmissions '85 and '86 that have the snout on the end of the input shaft, but do not have the provision for the bearing in the flywheel, just a big hole. He also said that some of the transmissions that came with the big bearing in the transmission case, Honda didn't feel needed the input shaft support bushing.

Though books and schematics are wonderful, they don't always have correct or complete information for every vehicle sold. It sure can cause confusion.

The first clutch kit I put in a '92 CX Honda came with a pilot shaft bushing and the pilot shaft only had splines, right to the tip. That was the first time I ever saw a manual transmission without a pilot shaft bushing. It took three calls to different Honda dealerships to get an answer to that one!
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Old 08-02-2008, 11:07 AM   #7
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though it sounds like you are getting poor mileage, I would never trust one fillup to measure the mpg. Try filling it at the same pump and letting it click off on its own and do this for a tank or two. Some pumps click off sooner then others.

I would pull the plugs and see if they are black in color. If it really is burning that much gas, it should be running pretty rich. I imagine your cat could be clogged as well, which would kill your mileage.
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Old 08-02-2008, 03:03 PM   #8
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What is your RPM in fifth gear at 60 MPH?

Could have a different transmission.

Does your shift indicator light work?

Are you driving in fifth gear at speeds as low as 30 MPH, and if so what is your tach reading at that speed?

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Old 08-02-2008, 04:52 PM   #9
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If the car has been modified then that is a bad sign. They could have done any number of things to the vehicle.

What condition are the tires in? Are they the stock size and do they have good tread on them? Are all four the same brand?

Get your alignment checked.

Get a compression check.

Make sure you have the right plugs. Many people make the mistake of using regular Civic plugs but the VX uses a different heat range.

Tell us how you are calculating your mpg.

Civic VX, D15Z7, 5 Speed LSD, AEM EMS, AEM UEGO, AEM Twin Fire, Distributor-less, Waste Spark
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Old 08-02-2008, 09:09 PM   #10
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took the o2 sensor out today it was pretty black, i bought a new one today and put it in. will post mpg from that when i finish driving the tank in the next few days..

theres no tach in my vx so i cant tell you what rpm im at on which gear.. can i buy a 92-95 civic cluster with a tach i heard its plug and play to get.

the alignment needs to be done, tires are all fine same size 175/70/13 @ 40psi.

just found out today my exhaust manifold is cracked so i gotta to replace that. didnt check the cat at all yet.

ill post back on my next fill up.

i calculate mpg by how many miles i drive the car on the cluster and divide it with how many gallons i pump at the station

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