'94 Civic VX idle/hesitation
 

Hi folks,

I bought a 94 civic VX this summer and I've been lurking on these forums collecting tips and ideas. I've been slowly tuning this car up and addressing a hesitation/inconsistent idle. I have read many tips on various forums about where to check and I'm only partway through the list. The car is all stock except for a cobbed on muffler that I'm about to replace. I recently replaced the plugs and wires with the recommended ones, as well as the cap/rotor, air filter. Timing belt, water pump and associated parts were just replaced, and valve timing that was off by a tooth was set right. The melted catalytic converter was just replaced, too.

The idle is not usually hunting or surging, though sometimes it is a little. Mostly it's just inconsistent -- in the 400 to 1000 range when warm or 1200 to 1500 when cold. The Hesitation is when I am cruising with little gas, there is a subtle but quite noticeable hesitation when you begin to accelerate. As in give it some more has and it sputters, then accelerates. Sometimes when going harder, too, there will be a stumbling and it almost seems like moving the gas pedal will change it -- not jus giving more gas but going back and forth a little. It's drivable, but annoying to me and I'm getting milage around 25 to 35. only a little better on highway.

If any of this points to something in particular, I'm happy to get suggestions even though I haven't exhausted the list of things to check.
One thing I have noticed while driving, however is that if I put the clutch in when I am coasting toward a stop and the engine goes to idle, it will actually surge quite a bit, then right when I come to a complete stop, it settles to an even idle--where ever that will be. As thought some condition in the engine management is changing when I actually stop. Does this sound normal, or point to any particular fault?

Thanks in advance. I've enjoyed reading all of your helpful hints so far.
If I left out any important details, let me know.

To your last point, I think it is very common/normal for these engines to idle higher when the car is moving than when it is at a complete stop. It does it on my VXes as well, especially at higher highway speeds, it will always be up around 900 or even 1000 when coasting at 60mph on the highway. As to the rest of your issues, eek, not sure. What RPMs do you usually shift at?

it sounds like you have a weak ignition system and/or a lean fuel mixture ... check your spark plugs and if you can get them bigger, do that or get some iridium spark plugs and gap them about 0.045 inches. I always like to recommend 3-4 oz acetone to 10 gallons of gas too.

Are you sure its not just going in and out of leanburn?

Do a compression test and check.vacuum. See what shape this motor is in. Always get a baseline to go off of.

I've recently driven three of these vx's and I bought my first one last Wednesday! I topped off the tank, drove it 185 miles, much of which was through red lights and then topped it off at the gas station at home. I checked my miles on my odometer and my friend's odometer who took me, and I did a map quest. My tank was full after 2.9 gallons. I continued topping it off much more than the previous fill up till the gas was actually about to spill over. I averaged 62 miles per gallon! I had read things like that and thought people were exagerating! I was and am thrilled. I'm mentioning this to strengthen your confidence that you can get this kind of performance and mpg's from the VX.

All three cars I drove had a very subtle shift in the rpm and power and I do think it is the "lean burn." From what I've read, the cars shut one valve per cylinder off at low RPM's and that causes the gas to swirl, atomize and burn more efficiently. You can feel the car get a little lift in power as it simultaneously drops RPM's! So my inexperienced, limited mechanical knowledge guess is that it has to do with that and that once you get that fixed it will change your entire performance drastically to the better!!!!

Wilcrass, how many miles on your newly acquired VX?

205k
 

It just turned 205,000. It doesn't smoke or leak any oil and seems to be fine! I'm putting some Low Resistance tires, changing the oil and transmission fluid. It has a new timing belt, water pump, cv joints, and plugs. I'd like to find some stock VX aluminum alloy wheels if anyone knows where some are for sale! thanks, Wil

Update...or something
 

I've been slowly working on this...

I replaced the PCV (took me a while to get up the courage because it's hard to get at). This seems to have helped with the idle a lot. It's not quite as stable as I'd expect from a new car, but with my MPGuino in now, also, I can see it's idling around 650, warmed up with no load.

If any one is still wondering, the Civic VX does have a pcv valve. It sticks right into the breather box. You want long skinny arms to reach it.

HOWEVER, still getting the hesitation at low throttle. It only seems to do this after it's warmed up, so I tried disconnecting the O2 sensor. Hesitation is gone and it drives like it does cold.

Think this means my o2 sensor is bad? or is there another culprit? I haven't ordered a new sensor yet, but I just looked around, and it seems If I'm sticking with the L1H1 as the one to get, oxygenSensors.net has the best deal at $190+ ...but they are saying it's the L2H2 as replacement. So any one know if that's really the same thing?

I'm going to go solder some wires in this afternoon to check voltage on the O2 sensor easily ...any idea what I should see if the sensor is BAD? (I know roughly what I should see if it's good)

Download the fsm from Hondahookups. It has a flow chart for testing it. No check engine light? Also check for a plugged cat. There is a writeup on here or on ecomodder for making a monitor for lean burn that ties into the 02 circuit. You grab the wires right at the ecu. You possibly don't want to tamper with those wires. I know that there was a tech bulletin for Volvo that involved the connector for the 02 and it allowing oxygen and false readings.