Hey everybody. Firstly, this is my first post here, and I just wanted to acknowledge how amazing this community is. I discovered the Civic VX from this site a year ago, and managed to find one that was in very good well maintained and surprisingly unmolested condition, with 182,000 miles on it. This 1993 Honda Civic VX was and is my first car.
Recently, I moved to California. For the last 3 weeks or so, I have been trying to get it to pass the emissions test here, in order to get it registered. Here is the emission test results:
I am not the most mechanically godlike person, however, I am good at learning about things. When my car first failed, I did a bunch of reading on various forums, and a whole bunch of learning about how my engine works (helped greatly by all of the awesome information on this site!)
My Story:
The first thing I tried was to check and change the spark plugs. I bought a set of NGK ZFR4F-11, and replaced the ZFR5F-11 plugs that were in the car. The plugs were clean, no carbon buildup, and no excess fuel present. The tip ceramic was slightly pink. I took it back to get re-tested, and there was no change.
There is an intermittent check engine light that comes on, usually when the car is run at higher rpms for a period of time, or when it is under heavy load. For example, accelerating in 3rd gear at 3000+ rpm for 20 seconds or more going onto the freeway can trigger it. I read the CEL error code and it is a code 22, which indicates a failure of the oil pressure switch in the spool valve assembly. I troubleshot it to the best of my ability with the troubleshooting diagnostic procedures in the
Honda Civic 92-95 Service Manual, not being able to test the oil pressure without "special tools".
Desperate and sad, I added 22ml of Acetone to the 3 gallons left in my gas tank, and took it in for another re-test. (I had read reports of using Acetone as an fuel additive reducing HC emissions by up to 60% and thought I would give it a try). There was no change in the test.
Finally, I decided that this problem was beyond my capabilities, and even in my desperate poverty, I took it to a well-regarded automotive smog shop that is a gold-certified smog repair facility (emissions testing laws in California are intense and complicated).
2 days later, I got a call back essentially saying "your car is confusing and we couldn't fix the problem, but we won't charge you money." I talked to the mechanic who worked on it, and it soon became apparent that I knew about as much about my engine as he did. He guessed that the problem was the VTEC engaging too soon, because of the extremely different %O2 readings between 15mph and 25mph. He said that the VTEC shouldn't engage until 3000 rpm. While I think the value is supposed to be somewhere around 2600 for the VX, and depends on a bunch of factors like gear, throttle, fuel-air mixture, and various other incomprehensible things, there is probably some truth to his diagnostic. They also said that the Catalytic converter was likely slightly depleted, because of the higher than average NOx readings, but that it should still be good, and it would not account for the extremely high HC readings at 25mph. They recommended that I take it to the dealer to get the VTEC mechanism troubleshot.
They said that they tested all of the obvious things, that is, ignition timing, O2 (LAF) sensor, tested for vacuum leaks, and so forth, and that everything checked out fine.
I have a vague memory of the guy I bought the car from telling me that he "adjusted the vtec down to 2300, which is where it is supposed to be". From what I have read, it seems that if you adjust the "VTEC Crossover Point" without calibrating fuel maps and timing (I don't really understand this well enough to talk about yet), it will seriously throw off the engine's tuning, and it can end up with the ECU telling the injectors to squirt way more fuel into the combustion chamber that can be burned, resulting in an overly rich mixture, which could result in a high HC failure in the emissions test.
The car itself runs fine. It gets between 36 to 44 miles per gallon (my best tank is 45 on freeway driving). There is a slight hesitation in acceleration that is noticeable sometimes at around 2200 rpm. It is very slight and ... non-violent, so I assumed this was related to the VTEC mechanism engaging. The car idles at about 1200 rpm when started cold, and eventually equalizes to about 900 rpm. Sometimes, after driving for a while, the idle will drop all the way to 400-500, but it never idles rough, or stalls. The engine burns about a quart of oil every 1000 miles.
With this evidence presented then, my question for you, kind compatriots of fuel economy questing, is:
How do I adjust the VTEC engagement point, and is this even possible? And more generally, what advice can you give me from your collectively vast VX VTEC-E knowledge that might help me pay less money to get my fabulous car to pass emissions?
Thank you greatly in advance, and I apologize for writing a novel on my first post! ;\
Linear Mode
