Another new VX owner

[vxguy]

I just acquired a '92 VX (teal). Man, are they hard to come by, especially a stock VX! I'm not a mechanic, so I've learned a lot already from this site.

Here's an issue I have: It's very difficult, if not impossible, to maintain a steady speed (at 55 or 60 mph for example). While trying to maintain a speed while highway driving (though I've noticed some of this behavior at other speeds), the engine hesitates or stutters, and then starts dropping speed. When I apply slight pressure to the pedal to maintain the speed and break through the hesitation, it then slowly keeps accelerating. So, I back off and the process starts all over again.

I've read a lot of threads on this site about O2 sensors, but I have no idea if that's the issue.

Only once has the CEL come one. About 10 minutes into highway trip, the light came on, but then actually started running much smoother and I was able to maintain a cruising speed. But that was only once, it's back to the behavior mentioned above. BTW, the shift indicator light rarely comes on.

I've only put about 600 miles on it so far, but I've put gas in it twice and recorded 45 mpg and 50 mpg, even running like I've described.

We added new plugs and filters, as well as a timing belt and rear muffler. Just the other day I bought some stock size 165/70 13 Sumitomo HTR T4s. I don't mind putting some money into this car to get it up to speed, so to speak. Price a hybrid lately, even a used one?! I'll still be ahead by $thousands before it's all said and done.

Thanks,
Rick

[GasSavers_BIBI]

try changing the spark plugs, but since you had a CEL, maybe your O2 sensor is the problem, but the spark plugs will be much cheaper to try first.

Make sure you get the good ones. "The VX uses NGK V-Power Spark Plugs No. ZFR4F-11".

And here is a good thread about the Civic VX: http://www.gassavers.org/showthread.php?p=49664

[jadziasman]

I had the exact same symptoms you described with my first VX. I could not maintain a steady speed by holding the gas pedal in one position. I had to keep "goosing" the pedal to avoid decelerating. I also got a code 48 - LAF sensor indication when driving at highway speed every once in a while that would disappear upon a restart.

I never did find out why my first VX had the throttle issue because I sold it in 2002. I have read that the throttle position sensors of Civics occasionally fail to operate properly through their full operating range. You should check the output of the TPS sensor - somehow.

Changing the LAF sensor (aka the O2 sensor) might help you as well. I never changed it on my first VX and have not changed the LAF on my current VX either since I have been getting 50 mpg which indicates to me that the sensor is still good.

Keep us posted on your progress. I've always wondered what the cause of the throttle problem was.

[vxguy]

OK. I checked my plugs and had NGK ZFR5J-11, and gapped a bit too small. Got excited thinking that must may be it. I have a parts store just a few blocks away, so I got the ZFR4F-11, gapped them correctly, and went on a test drive. Results:

Same symptoms, but then at around 5 miles out, the CEL came on and it immediately ran smooth and I could hold the speed with no problem, just like the only other time the light came on. Went 5 more miles, stopped, shut it off. Then drove 10 miles back and CEL did not come on and ran rough again.

Thanks

[vxguy]

I read up on how to check the CEL code from the instructions found on this site. It's giving me a code #48. LAF sensor issue, and is that the same thing as an O2 sensor?

[1993CivicVX]

Originally Posted by vxguy

OK. I checked my plugs and had NGK ZFR5J-11, and gapped a bit too small. Got excited thinking that must may be it. I have a parts store just a few blocks away, so I got the ZFR4F-11, gapped them correctly, and went on a test drive. Results:

Same symptoms, but then at around 5 miles out, the CEL came on and it immediately ran smooth and I could hold the speed with no problem, just like the only other time the light came on. Went 5 more miles, stopped, shut it off. Then drove 10 miles back and CEL did not come on and ran rough again.

Thanks

Please listen to me. It's your o2 sensor. My car did the exact same thing, except mine never got so bad that the CEL came on. You can check the code using a paper clip. Have one ready and the next time the CEL comes on use a paper clip. I don't remember the exact procedure, but if you search "CEL o2 sensor paper clip" without the quotes on these forums you'll find the answer! You're looking for code 48. good luck.

SVOBoy said: Find the little blue plug tucked up under the dash on the passenger side and jump it with a paper clip and then watch the CEL flash. Long = 10, short = 1, tell us what the code is...

There should be a blue one with 3 pins and a blue one with 2 pins. Put the two ends of the paper clip in the jumper with 2 pins.

http://crxmpg.com/obd1ecucodes.html

^^^ use the above link to see what the code refers to.

[vxguy]

Hey 1993CivicVX,

As suggested, I did the paperclip trick to flash the code on the CEL. 48 was the result. So, I've been surfing the net for O2 sensors. Best prices I've found are on eBay. One for $80 that claims to be an NTK 5 wire and waiting to hear back to confirm, and another for $170 who did reply back saying it is an NTK 24300.

If a new O2 doesn't solve the issue, I've been reading about all kinds of suggestions on other threads suggesting replacement of the TPS, clean the EGR, and vacuum leaks as potential culprits. I suppose I could change the wires, cap, and rotor while I'm at it.

Great site. Thanks for all the input from all of you!

[theholycow]

If the TPS is anything like one I've tested before, it's easy to test with a multimeter set to measure resistance. Just hook it up and watch the meter as you move the TPS through its range.

[theholycow]

Edit: I'm a dumbass. If you remember what I deleted here, ignore it. The rest should still apply.

When the CEL comes on it's likely that the computer is ignoring the bad LAF data and using pre-fabricated lookup tables to guess what value the sensor might provide if it were good. That results in it running smoother but not as efficiently and clean as possible.

[jadziasman]

HOLY COW!!!!!

The LAF stands for Linear Air Fuel and it is a wideband O2 sensor that measures the amount of oxygen in the exhaust. It is screwed into the exhaust manifold. It is capable of measuring air fuel mixtures from 12:1 to 25:1. Its response is generally linear hence the acronym.