Hi guys im a newbie to this forum and this is my first crx w/ a b18c. I had this car with the swapped b18c for two years now and the last 3 months is when problems started happening. This is my problem, my Vtec only engages the first 1/4 mile and that’s it. After that quick ¼ mile run I’ll come to a complete stop and ill roll slowly in 1st gear and shift into 2nd gear and when im at 4000 rpm ill get on the gas and no Vtec..?? The rpms will go all the way up to 8000 rpms but very slowly and its having a hard time getting up there and vtec never engages. When I go to work every morning ill get on the gas after the car warms up to proper temps and again vtec only engages once and after that no more.
The solenoid is working I tried two already. The oil pressure switch cant be bad, because vtec engages everyday but only one time a day. Everything is grounded properly. I tried two ECU’s already and the same results. The oil is at proper level. The oil pan isn’t dented. Speedo works. Rpm’s works. I flushed inside the motor last month. I checked the Ecu wire and the piggy harness and everything is plugged in snug and tight. The radiator is filled and the fan works. There are no blown fuses. My car thrown a code the other day on the freeway when I was in 5th going about 95-100 and I let off the gas a little then got back into 4000 rpm’s and check Engine light came on. I wasnt able to retrieve the code.
Has anybody ever heard or had this problem? Is there anything else I can check/ replace to fix this problem I’m having. I don’t want to give up on the car. Please shed some light my way.

 

Sorry, but Engine Tech & Tuning is the place for threads like these.
Moved.

How have you handled the knock sensor input? :thinking:
That the only item you haven't mentioned and 9 of 10 times, the problem with these sorts of engine swap is wiring related.

If only you could retrieve that CEL code.. h:

 

vtec will still engage on a obd1 gsr ecu without a knock sensor, i know first hand, when i broke mine i drove it around a little with out it, and the only problem i had was a check engine light. vtec was there all day

 

Thats what my buddy at the shop told me, that the knock sensor wont effect the Vtec engagement(obd1). I have'nt changed out my spark plugs in a year so i'm going to pull them out check them, but im still going to buy and replace with some new spark plugs. Would a bad spark plug or too hot of a spark plug effect the vtec from engaging? Im also thinking of flushing the engine out one more time because the first flush might have loosen the build up gunk and now it could be floating around and clogging the wholes? I dont know......

 

Sounds to me like an ECU or electronic related problem... If it only works once, then not again, and it does this CONSISTENTLY, then I would have to think it is something in the ECU turning off VTEC engagement...
U say u tried 2 ECU's, then it's gotta be a sensor... Check your grounds, this could be it... Maybe when the car gets warmer, it loses contact with the ground... Check it FIRST!!
VTEC needs the following sensor inputs to work:
-engine load (MAP sensor)
-engine temperature
-oil pressure
-throttle position
-knock sensor
-IAT sensor? (not sure)
-might be another sensor I can't think of

It could be that one of these sensors is telling the ecu "hey man, vtec doesn't work right, I'm turning it off" - could be the ground not being "good" enough...

Hope this helps, good luck!

 

Okay, how would i check to find out if my engine load (map sensor) is good and how would i check to see if the IAT senor is good? The throttle position? Is there a senor for that? how would the ECU know the position the throttle is in? i relocated the battery to the back of the car. I grounded the battery 1 foot away from its new location. it is also grounded to the engine and there is two ground wires on the valve cover to the body. I also have a ground wire from the engine to the body. Im i missing any grounds?

 

1. You check the sensors with a voltmeter. I highly suggest you go and buy a repair manual, it will help immensely.

2. Yes there is a Thottle Position sensor (TPS), and it "tells" the ecu the position by transferring a voltage to the ecu, when the throttle is closed, like 0.5 volts is sent to the ecu, so it know the throttle is closed, and the gas pedal is not being pressed. It is a linear relationship, where the voltage increases linearly as the throttle is opened, to a max of 4.5V. So, the ecu "knows" simply by reading a voltage.

3. As for the grounds issue, good luck man, I had a hell of a time diagnosing a misfiring problem. I can't tell you if you are missing any. U gotta look.

Again, go buy a repair manual, it's the best way to do these tests

 

All my wiring is good. I checked all senors and they are good. I'm going to check the oil pressure, i have a feeling that it might be the oil pump. could somebody please guide me on how to check the oil pressure?