Okay, I warmed up the car this morning before driving it (cold here in Williams Lake B.C.) then headed out to work. I stopped at the stop sign and was taking off when I changed gears from 2nd to 3rd and as I hit 6000rpm the Vtec kicked in then at the exact moment it kicked in it kicked out and now it does not work. Was aquick "blip" of vtecthen nothing.Also the speedo isn't reading anymore.. Weird..
I will check the oil and fuses on my lunch, does anyone know what else it could be? Maybe a knock sensor or a vtec solenoid?? BAHhh Help needed!!! Will update after lunch.

OH!!! Also when I was passing I was holding the pedal to the floor and it started to spike on me. (this was at around 4-5000rpm) The rev's were fluctuating between 4-6g, up and down radically. It kind of sounded like a 1ga dsm hitting a pre-set rev limiter. So I let off the gasoline and held it at 70% and it ran fine. 5 more mins down the road I opened it up again but it did not spike and still no Vtec... Maybe the wiring is hokey?? sigh... I Don't know!!! Any suggestions??

 

Could be numerous things... I would start with these things in order, and test in between. Eliminate the cheap things first.

1. Check all fuzes... typically this would throw a CEL though within a few 10 miles...
2. REALLY dirty intake filter or blockage. MassAirflowSensor knows when its getting a limited air supply and will shut your vtec system down to safe mode if this happened you need to reset the ECU after fixing... I spent LOTS of hours looking for a vtec issue on a newer prelude before fixing a stupid aftermarket dirty filter, I replaced the whole head and all the valves, I was not a happy camper.
3. Low oil levels, just 3/4 quart low and vtec will get flaky. Vtec runs on oil pressure to switch to the vtec cam lobes.
4. Distrubtor this is a very slight chance, but a defective or dirty connections in the dizzy can replicate like symptoms...
5. Check for spark at all the plugs and look for fouled plugs.
6. Reset the ECU, disconnect the battery for 4-5 mins from the ground, then start the car and let it sit for 1-2 mins before touching the throttle to test it.
7. Vtec selonoid, I think you need a voltage meter to test this.
8. ...could possibly be a bad sensor, I'm not sure on this one.

 

Well.. I checked all the fuses and two were burnt out. Replaced those and no clue what they fixed. Still no vtec nor speedo. Yesterday my radar detector started telling me "LOW VOLTAGE" over and over until that quit on me. Also it takes a couple times to try to start the car, its a push button start so I push it and nothing happens, other than a click but I try a couple times then it finally turns over and runs. Then all of a sudden the tach stopped working and at the lights started to dim. SOoo... Maybe my alternator or battery is hooped. Later today im going to do a load test and see what is going on. Do you think a faulty alternator or battery would cause this? Also I have seen these symptoms with a faulty ECU so maybe that is going... I did the old smack the ecu as the car is running but nothing happened so im leaning towards something in the charging system. I have never heard of accessories going before the car dies though... WEIRD!!!
Oh and the oil lev is good, air filter is great and ill check the distributor when I do the load test...

 

When the ECU detects any sort of problem, it will enter "limp home" mode which means no VTEC and rev limiter around 5000. So fix the voltage and speedometer problems first (the ECU needs vehicle speed signal too) and the VTEC will probably start working again.

 

have you checked all your ground wires?

 

I was just informed to do a thorough check. I did have some grounds off when installing my cam gears and I did have to disconnect the alternator to install the pulleys. Ill check all that after work today. Also I forgot to mention I have overdrive pulleys and they could be the cause to my problems. Im going to start up the car and run it, then take off the positive lead on the battery. If she runs, then im presuming its the battery that needs to be changed and I will NOT recommend getting overdrive/under drive pulleys!! (that still does not explain why the speedo suddenly stopped, maybe not enough voltage?) Anyhow, will update later!!

 

Do NOT disconnect the battery while the engine is running! That test was marginally acceptable in the 1950's, but do it to a modern car and a lot of costly electronic stuff can be burned out.

Test with a volt meter instead. All indications are that you don't have any output from the charging system. The underdrive pulleys probably aren't the problem, but put the stock one back on anyway. If you charge the battery fully with a battery charger or swap in a charged one, it should run for a while until the battery runs down again. The speedometer should work anyway. The VTEC may not until the ECU can confirm full operation of the alternator.

 

Thanks for the info, ill think I'll keep my costly electrical stuff in-tact lol...
I was a little sketchy about pulling the positive off but I got talked into it from a friend. Okay, so that option is out of the way!!! I did test with a volt metre but I decided not to post that outcome because it's a hokey Canadian Tire specialty and it usually has 3 different outcomes anyhow.. lol! But what it said was 11.36 volts and when I turned on the accessories (lights, heater blah blah) and revved a couple more grand than idle, nothing happened on the metre. But of course a second later it read 0.3-0.2 and stayed there... So I decided it was a failed attempt and will purchase another ASAP. So if it were correct, that would tell me something in the charging system is failing. Or as Basil stated it could be in the grounding.
Btw, what is the normal amperature (max output) for a 99 SI alternator? I got a quote from a local parts dealer for $278.00 and that's an 80amp. Im going to do a bit of research, maybe an Acura alternator puts out a bit more and would make up for the lost revolutions from the pulleys. (geez I need to get a Haynes soon) Your right though mk378 I probably should ditch the pulleys, there's gota be loop hole to my problem!!!!
PS. Thanks for all the replies, it's helping me a lot!!!

 

if everything is in working order, and you dont have a 10,000 watt amp and 25 subs, your factory alternator will suffice. with the engine off, check the voltage from the positive and negative posts of your battery. should read 11.5 - 12.5. start the motor and do the same test, should read 13.5 - 14.5 no matter how much load you have on the system. if it reads any less, replace your alternator (or take off the underdrive pully and perform the same test)

 

Well, problem found!...(ish)
After I found the alternator was doing absolutely nothing we were about to swap it with a bran new one until I was doing some research and I found that your alternator/speedo signals go threw the same fuse (the one that somehow I must have missed) #15 in fuse box. Also if your speedo is not working it turns out somehow your vtec will not engage. Maybe it's a limp mode or something. So the fuse is changed and everything works awesome. UNTIL it does it again and again so she runs but I have to have a hand full of fuses with me. SOoo now I have to find out why it keeps kicking the fuses out!!