SFC-VTEC controller problem (long)... - Honda Prelude Forum

VitaminZ · 02-01-2002, 07:47 PM

Hi!
I have a problem. This is how it started.

From the letter to a fellow luder
â€œAbout a month ago I was driving to work and right before I stopped at the light my idle went up and dropped down to about 500 rpms. Check engine light came on. The engine sounded like it was about to die so I actually had to keep my foot on the pedal to keep it from stalling (Iâ€™m not going to tell you what kind of thoughts went through my mind but there was a lot of cursing involved). I immediately went to see a mechanic (sort of a friend of my family). While I was driving there (about 5 min away) I had to really push the paddle to keep the car moving. When I got there and stopped, the rpms dropped to 500 and after a few seconds it died. I want inside and told him about my adventures so he told me do drive it inside the shop so they can get the code off of the computer. When I started the car it was fine (talking about those stories involving cars and mechanics). It was running perfect no check engine light; the idle was back to normal. After about 15 min he told me that he can not get the code because somebody (previous owner) had already screwed with ECU (he hooked up a Field VTEC controller but never actually tuned it â€“ so it was off) and he can not get the code. He recommended going to a dealer and letting them get the code so we would know what is going on. That is exactly what I did.
A few hours later the dealer called me and told me that both of my CV boots were leaking grease and my slave cylinder was also leaking but there is no code in the computer what so ever. So I picked up the car, which did not show any signs of previous behavior. We took care of the above problems that the dealer found and I kept driving my car for about 2 weeks (even went to NC for New Years) than suddenly one day (a week later) it happened again. Exact same symptoms with check engine light on. When the car died at the light I stared it again and it was fine. About 15 min later it did it again and again restarting it took care of the problem. About 10 min later the same thing, only this time restarting it did not help. It would idle around 500 for about 5 sec and then stall. So on the start I had to push the gas paddle to keep it from stalling and really keep it on high rpms in order for it not to stall on me. After work (5 hours later) I started it and it was doing the same thing, light is on and the Prelude is stalling. Kept it at high idle all the way home. About 4 times it died on me. When it stalled once more, after restarting it the problem went away, however I felt a slight lack of power while driving.
The next day I took it to a dealer. This time they said that the computer came up with the following, â€œfound map sensor code. Followed flow chart â€“ not able to determine exact cause at this timeâ€?. Really helpful, right? Not only that they werenâ€™t sure of the cause of the problem but also they wanted $537 for the job of replacing the â€œfaultyâ€? sensor. They also recommended to bring in the car when the check engine light was on (those ignorant bustards, like I wasnâ€™t trying to do this all along) And of course I told them where to stick it and if they were not sure where, I can stick it there for themâ€¦well you know.
So know at least I knew where to begin. The car was back to normal. A few days later it happened all over again. And the thing is, I can fell when it is about to happen because while driving I start to notice a lake of power and from time to time it feels like it chokes, just for a second. Iâ€™ve ordered a new sensor from B.C. Imports for $193 (what a rip off, for this little, cheap looking, plastic thing) and it will get here some time next week. I pray to VTEC gods that this is the problem. For now I drive my old POS Sentra. If the sensor will not help then I guess it is a dealer again. I hope it is not an ECU thatâ€™s going bad.
Sorry for a long story but Iâ€™m a bit pissed of â€˜cause I just got the car 2 months ago. I also had a Lude (exact same one, as a matter of fact you can see it under my profile) and it was perfect, but I was notâ€¦Donâ€™t drink and drive, and watch out for telephone poles, they are trickyâ€¦â€?

Now I got a new MAP Sensor and it is not the problem.
However, I found something else and it has something to do with the SFC-VTEC controller (I did not install it, it came with a car from the previous owner).
Previously I switch it off to make sure it was not the VTEC controller but I never unplugged it.
Now what I found is that when I unplug the harness it immediately drops the rpms and after a few seconds the car stoles. After restarting, if the controller is not plugged in the car stoles immediately (the check engine light is on) but if the harness is plugged in the check engine light is not on (at least not for the period of time that I ran it) and it is working smoothly until I rave it (and then after I let go of the gas paddle it drops to about 500 rpms but it does recover from it).

My question is for people with VTEC controllers (and everybody else). During the installation of the controller is the ECU altered in any way? If yes, can I undo it or do I have to buy a new ECU? If not, how can I unhook it and bring it back to factory settings.

Any help would be greatly appreciated.

BryanS · 02-03-2002, 02:20 AM

I have no idea what could be causing the problem, but to my knowledge, a VTEC controller is just wired into the ecu wiring. It does not require any alteration of the ecu itself. I might suggest that if you have removed the VTEC controller, you try resetting the ecu by removing the neg battery cable for a few minutes. It couldn't hurt anything and might help alleviate the problem.

bb2'95 · 02-03-2002, 03:36 PM

my friend had the same vtec controller, and it also caused his car to stall... he just took it out, sounds like its more of a pain in the ass then anything else..

91LegunaSi · 02-04-2002, 08:02 AM

So you are having problems with your SAFC thats connected to your ECU huh?

Well i used to have one of those in my car.

See what it does is connect directly to the "brain" of your ECU. Those controllers have to be programmed in order to run efficently. The asshole that sold you the car probably screwed with it himself, messed it up and wanted to get a quick turnaround on the car. Each prelude (because there is no one specific programming) has its own settings for the SAFC. What I suggest you do, is take it to a shop that knows how to program those things and they will tune it so your car is running sound. FYI, people that screw with the SAFC and do not know what they are doing have a more likely chance of damaging the engine than anything else. I know have a VAFC installed so its a little bit more complicated than yours. They will charge you about $75 dollars for the mods but it will be worth it because you will also be saving 5-10 mpg... if not better.

JDM Lude · 02-04-2002, 08:18 AM

When you get a MAP sensor code, the ECU goes into limp mode. thats what causes the car to run bad & stall. The car does that to protect itself basically.

The V-AFC wires into the MAP sensor signal. That means that the wire to the ECU is cut, and goes into the VAFC, and then there is a VAFC that goes to the ECU. the VAFC modifies the signal, so that the car thinks it should run richer or leaner. do this:

- pull the carpet up, and check all connections at the ECU.

- put the VAFC to a stock fuel curve and stock VTEC engagement

- set up the VAFC as follows (IMPORTANT!):

# of cly. 4
throttle up arrow
IN 06
OUT 06

Drive the car around for a while and make sure it works ok. Chances are, one of two things are happening:

- some part of the VAFC configuration is inncorrect or the wiring is faulty. This will either cause a value to be reported to the ECU outside of the normal range, making the ECU think that the MAP sensor is faulty (which causes it to ignore the sensor, go into limp mode, and throw a code) OR if the wiring is faulty, then the ECU will not see the MAP sensor at all, and once again think it is faulty.

to save yourself the hassle, I would pull the codes yourself. there is a two-wire terminal behind the center console on the driver side. turn the car off, stick a paperclip in the holes to jump the terminal, and then turn the ignition on (but don't start the car) the CE light will flash a pattern, which you can look up in ther service manual or on the internet.

I've had to deal with VAFC problems A LOT. Mine however, is now bug-free and it is very much worth it.

BryanS · 02-04-2002, 09:40 AM

did I read his post wrong or is he stuck with the Field VTEC controller rather than the Apexi AFC-V, and are they operated the same.... I don't have either (yet) but believe that the settings you gave were for the AFC-V

The Acclude · 02-04-2002, 10:12 PM

Sounds like the guy ****ed up the throttle signal or the rpm signal when wiring(if the SAFC has that). Otherwise try replacing your Rotor,ignitor chip and cap in the distributor....in that order.