Hi,
I gave up searching for a thread on this so I am starting a new thread. If someone can point me to an existing thread that would be great.

My Problem:
I have a 99 Civic EX D16Y8. Sometimes my VTEC engages at 5500-6000 RPM like it should, and other times it doesn't. The engine is at normal operating temp, coolant levels are normal, and oil level is normal. The VTEC engagement is sporadic, it feels like winning the lottery when it actually does what it suppose to.

I installed a VTEC light to help me observe what's going on. I had a low grade oil seep coming from the oil pan gasket, which I replaced and fixed today. I thought maybe that was messing with my oil pressure, and causing the problem. I got in the car drove around for a bit, and the VTEC was behaving. I thought I fixed it... A few minutes ago I went to the store and decided to give another go at testing the mechanism, and this time no VTEC. My VTEC light has three phases:
1) off
2) dim but lit, like its getting a signal
3) Bright as hell, and I can hear the VTEC cross over
Tonight, like so many other nights, the light would go dim at 5500 - 7000 RPM but no VTEC crossover. I can hold the motor at 5500 RPM, light turns dim like its getting a signal, and wait for about 5 - 10 seconds then the VTEC engages, and the light goes bright.

I checked the voltage across the VTEC Solenoid and it was in spec. I checked the voltage across VTEC Pressure Switch and it was in spec. I pulled apart and cleaned the VTEC Solenoid, but it didn't help. The next thing on the list is to check the oil pressure at the VTEC oil pressure switch.

Am I missing something here? Has anyone else had this problem? Is there a special connector I need to mate with the oil pressure switch? I need to buy a oil pressure tester, but I doubt a Pep Boys special will fit.

Thanks

 

Does the CEL work? Is it ON? Have you tried to pull codes from the ECU? Is the engine low on oil?

Have you check for resistance and a clogged filter on the VTEC solenoid?

 

Hi Ron,
No the CEL is not on, but it does work.
I don't have a reader for the ECU, but that is a great idea.
The engine has new oil in it, and in the past the oil on the dip stick hovers around the full mark +- 1/16 inch.
I did check the impedance across the solenoid, and I did pull it apart to clean it.

I followed all the trouble shooting steps from the manual that I could. Some I don't have the right tools to perform

 

By the way, you don't need a code reader to pull CEL codes from your Civic (see CEL link in my signature).

I also assume that you measured resistance (Ohms) rather than impedance of the solenoid.

I agree that measuring the oil pressure is a logical next step. Based on information you have provided, however, my guess is that the pressure switch may be faulty.

 

I assume your light is simply wired in parallel with the solenoid. When it comes on dim, the VTEC is trying to engage but the soleniod is not receiving full voltage. This could be one of 3 reasons:

Bad connection in the wiring, either from the power source to the solenoid or the solenoid to the ECU. Or lack of power from the power source.


Partially shorted soleniod. The ohm test should find that, but since your problem is intermittent you can't be sure you're testing at the same time the problem is occuring. If you have another solenoid handy, you should try just swapping it out.

Or lastly, and somewhat unlikely, a faulty ECU. It is not supplying proper drive power to the VTEC solenoid.


To test the engine oil pressure (also a good idea), unscrew the oil warning light switch from the block above the oil filter, and connect your tester there. It is standard 1/8 NPT thread.

 

Cool I'll check the CEL codes and the oil pressure and see what I can find out.

 

Hi Ron,
I checked the CEL codes using your link. The engine light stayed on and never blinked any codes so I am assuming that means there are no codes stored. I'll do oil pressure next

Thanks

 

Yep, no codes were stored in the ECU.

 

So I have some updates on my VTEC problem:

I replaced the VTEC solenoid with a working one, and I observed the same behavior as I described in my previous posts. I tested both solenoids (the new and old) by supplying a 12v signal, and both clicked on with no problems. I also bought and replaced the gaskets for the solenoid.

I bypassed the VTEC oil pressure switch at the ECU to eliminate it from the equation, but that made no difference. Same behavior so I reconnected the switch.

I re-wired the VTEC solenoid bypassing the stock wiring, but there was no change in the behavior.

I checked the inputs coming into the ECU: VSS, ECT, and VTM:
ECT (Engine Coolant Temp pin C26) = 0.69v
VSS (Vehicle Speed Sensor pin C23) = 2.3 - 2.5v
VTM - (VTEC Pressure Switch pin C10) = 13.36v with VTEC engaged

I couldn't find the RPM sensor, is this part of the VSS? I saw a Black/Yellow lead that didn't map to any of the connectors going into the ECU.

One interesting thing I noted is when the light is dim the ECU is only supplying ~5.6v, then when the VTEC finally decides to engage it jumps up to 13.36v

I'm thinking the ECU is faulty. I bought this car used, so the possibility exists that it's always been faulty, and the previous owners didn't notice. What do you guys think? Are there any other tests I should perform before dumping cash into a new ECU?

Thanks

 

The engine rpm signal for the ECU comes from the Yel/Grn wire attached to the ICM in the distributor. Are you experiencing any tach problems?

More info might help. Where in the VTEC circuit is the VTEC indicator light connected? Where in the VTEC circuit did you measure the 5.6V and 13.36V variable ECU output?

It also seems quite possible that the ECU is bad. Do you happen to know anyone who has the same ECU so that you could verify that an ECU swap fixes the problem?