i can't figure this out. when the car warms up in the morning, vtec works fine. after a few miles of driving, vtec starts engaging later, closer to 6k rpm instead of 5200. then it will not work at all. sometimes, vtec engages at 5200, and stops around 6500, then engages again at 7k, then stops at 7500. redline set at stock 8200.

the motor is a b16a2, previous owner said it has crower stage 2 na camshafts, but i doubt it. I've tried replacing the vtec solenoid, engine coolant temp sensor, ecu, and vss. I'm out of ideas. motor is in a 1995 si hatch. no cels come on. both ecus I've tried are chipped p28s

help?

 

Motor is probly blown! Most likely the head needs a valve adjustment. Just my .02

 

Read through this to see if it can help you out.

https://honda-tech.com/forums/honda-prelude-4/official-%22why-vtec-doesnt-engage%22-thread-830163/

 

what about trying an oem 99-00 Si ecu that hasnt been tinkered with?

 

i can't, the wiring harness is obd1, id have to get a whole new harness, and even then, i don't think it would work with the car

 

has this been happening ever since you got the car?

 

yes, tried contacting previous owner, claims it wasn't happening when he sold it to me.

 

that totally blows, i feel for you dude, I bought my EM1 and basically didnt realize the engine was shot, I had to have the engine rebuilt.

 

Man that sucks if its blown. Happens though. friend got a EG with a blown motor. He had no idea. Had to rebuild as well.

 

I had a similar issue before, i would pay close attention to coolant temperature at what temps it cuts out, i had a blown head gasket issue in my boosted gsr that seemed to be doing similar things, stock temp gauge in the car would not even be over the halfway mark and it was still running to hot after driving in boost for a while, just an idea see if you can find an accurate temp gauge setup and monitor the temp while the problems are occuring, my blown head gasket passed a block test with flying colors, but if i let the engine run for a while with the rad cap off i would get tiny bubbles consistently coming to the top, this was the give away for me, i suppose this may not be the case for you, but i was tuned and it may have been built in to the tune on mine somehow

 

hmmmm good idea. I'm going to also get an oil pressure gauge to make sure oil pressure isn't dropping off after the car has been running for a bit.

 

I'm having the same problem in my 97 ex d16y8 vtec engages when it wants to now, previous owner said the same thing didn't happen to him he says

 

bumpppp any more ideas? maybe ron has some input I'm hoping? lol

 

Does the CEL work? Is it coming on?

 

cel works, no its not coming on. i know it works cuz i unplugged the coolant temp sensor and it threw a code. plugged it back in, reset the ecu and its off now. this is so frustrating

 

Run the proper ECU for the motor, or run a known good basemap for your ECU. If the CEL isn't coming on, good chances lean on either A) vtec is working correctly, or B) your ECU isn't controlling it correctly.

 

Check all electrical wires/sensors. The do mechanical VTEC checks.

 

vtec is defiantly working correctly...when it actually works. and I've tried three different ecu's, all with a b16 basemap.

 

all connections for the engine were thoroughly cleaned and plugged in, and all were triple checked

 

Have you checked the vtec oil pressure switch, maybe it has something to do with that, the car gets warmed all the way up oil pressure does drop off some this drop in oil pressure compared to oil pressure after engine start up and possibly a faulty oil pressure switch may be tied into the problem, also have you tried a manual oil pressure test yet? most shops should be able to help you with this im sure for a normal 1 hour diagnostic charge, if you dont have the tool yourself

 

The oil pressure switch has been.bypassed at the ecu.. I thought that was the problem too. but that was the first thing that was changed to try and make it work... I know him. Im trying to help him fix it

 

bump, any other ideas?

 

I'm thinking it might be the map sensor, any thoughts before i empty my wallet for one?

 

does anyone have a link to a thread on how to wire vtec im doing my first vtec engine swap soon and i know a lil but not enough

 

Use google and don't thread jack.

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