VTEC stops kicking in after running hard for 15 minutes - Honda Prelude Forum

redneck2 · 07-06-2011, 08:58 AM

I know there are a ton of questions on the VTEC not kicking in but i havent found any answers to mine....I have a 93 prelude, new plugs/wires/distributor cap, oil sensor....

After i run it hard for around 15-20min the CEL will come on and the VTEC quites working. When i shut it off the CEL goes away and doesnt store any codes. I have swapped computers without luck. My engine is full of oil, compression tests are good. The car doesnt appear to be overheating. I have also changed the coil and added a code air intake. Any suggestions?

I ordered a distributor.....?X??

MisledYouth bb6 · 07-06-2011, 10:32 AM

The CEL that is coming on is probably your vtec not engaging(that is actual code for it) so after you shut off the car it clears itself of the code. See if you can get a scanner hooked up to the car and see what code it is before shutting off the car.

redneck2 · 07-06-2011, 11:37 AM

Good idea, if i had a code reader....I might have to buy one.

MisledYouth bb6 · 07-06-2011, 01:16 PM

You can always do the paper clip and read them manually so you can save the money to fix the problem.

redneck2 · 07-06-2011, 08:28 PM

I thought you had to shut down power before plugging into the error code connector.....

Agrat · 07-06-2011, 09:40 PM

I had that problem with my sister's b16a2. We noticed it after we changed the oil to full synthetic. If you're running synthetic, try changing to semi-synthetic, and the problems should go away.

schmitty915 · 07-07-2011, 07:28 AM

have you tried cleaning your VTEC solenoid or replacing the screen?

TypeT · 07-07-2011, 08:55 AM

some cars vtec wont engage if they dont have enough oil in engine

..and have you checked ecu and other wires?

redneck2 · 07-07-2011, 11:34 PM

Thanks for all the inputs.... I have cleaned my vtec screen and the oil level is good. I have swapped out ECU's and get the same results.

It seems to me that since it runs perfect for 16 laps (I race this car) then the CEL lights up and the VTEC stops operating...that something is getting hot. During qualifying at heat laps (around 10 laps) this car is perfect, but the races are 20-30 laps and this is where its a problem.

Also, the valves were recently adjusted, compression is good, plugs,wires and distributor are new....Im running 20w-50Valvoline racing oil.

Again, thanks for any input....i appreciate it

merlinbadman · 07-08-2011, 06:01 AM

Without knowing the code your going to be guessing what the probelm is. As soon as the CEL comes on, the fault is stored by the ECU. When doing the paper clip test all stored codes are displayed. Best to clear all stored codes (remove clock/radio fuse for 10-20 seconds) then run the car untill the fault appears, then pull the code. This way when you go to pull the codes only the recent one will show.

Slatelude · 07-10-2011, 01:30 PM

Quote:

Originally Posted by redneck2

Also, the valves were recently adjusted, compression is good, plugs,wires and distributor are new....Im running 20w-50Valvoline racing oil.

now don't get all offended because I understand the logic, but knowing that VTEC is operated by oil pressure..could this have something to do with it? I'm not an oil expert, but could the weight/viscosity breakdown over 10-15mins of hard driving make it not engage? Our motors were designed to work with 5W-30 from factory, and obviously running a 20W-50 would be thicker/make pressure changes in your motor?

but yeah, as soon as that thing lights up, run that bad boy to Autozone and get them to plug in their code reader, at least that way you'll know what's gettin' ya.

Agrat · 07-10-2011, 04:11 PM

Quote:

Originally Posted by Slatelude

now don't get all offended because I understand the logic, but knowing that VTEC is operated by oil pressure..could this have something to do with it? I'm not an oil expert, but could the weight/viscosity breakdown over 10-15mins of hard driving make it not engage? Our motors were designed to work with 5W-30 from factory, and obviously running a 20W-50 would be thicker/make pressure changes in your motor?

but yeah, as soon as that thing lights up, run that bad boy to Autozone and get them to plug in their code reader, at least that way you'll know what's gettin' ya.

Yeah, definitely try changing your oil back to 5w-30.

minilogoguy18 · 07-10-2011, 08:31 PM

Changing the oil constantly will have little effect if the oil pressure isn't high enough for VTEC to function. It is a built in fail safe and usually tells you that something is wrong if VTEC doesn't work, you may have a loss of oil pressure either caused by a clogged pick up or failing oil pump. Since you are getting no CEL for a problem with the circuit you need to check the oil pressure, don't be like the guy in the other thread who just killed his engine by running it with low oil pressure.