I need help, I just bought and put on a new 99 si head for my gsr block. However, there is no vtec. Why?

 

Any check engine lights? Plug everything back in?

 

yes, it reads o2 senor and somethings about coolant senor. But I checked all the plugs and rewired the wires and it still has this problem. I event change my thermostats for my heating. also there is no oil or coolant leak.

 

https://honda-tech.com/zerothread?id=1812135

 

Well, every consider you may have a bad o2 senser?

 

not yet, do i have to replace it? I''ll check on it. However I'm using a obd1 ecu, so only one o2 sensor, the one by the headers should be pulged in right?

 

OK. NO vtec, I thinK I'll have to take it apart and try to redo everything.

 

have you tried a different o2 sensor yet?

 

yes, but I just bought new cams so I'll built the motor now and I will switch the o2 sensor. Thank All for your help.

 

could be ur temperature sensor

 

Fix the temperature sensor. VTEC isn't supposed to engage until the engine is warmed up.

 

I change my thermostats, but I'll check up on the temperature sensor. Also do I just change the plugs for the temperature sensor?

 

Well, maybe not JUST the plugs. The temperature sensor for the ECU is a 2-wire sensor in the end of the head near the distributor. If the wire or connector is loose or corroded (or broken?) then that's what you have to fix. The Helm repair book has a small chart says what electrical resistance the sensor is SUPPOSED to have at different temperatures. Check with an ohm-meter against that chart (sensor in a bucket of hot water with a thermometer).

Bottom line is, if the computer thinks the engine's NOT warmed up, it won't engage VTEC.

For VTEC to engage, all the following stuff has to be OK:
oil pressure (VTEC oil pressure switch)
coolant temperature (ECT sensor OK & engine warmed up)
road speed (VSS & speedometer OK)
RPM (tachometer working)
throttle (TPS)

 

thanks for your help i'll check it.

 

Where is the coolant temperature (ECT sensor) Located?

 

End of the head near the distributor.

VTEC oil pressure switch has a 2-wire plug, this sensor is located on the VTEC spool valve.

ECT sensor has a 2-wire plug, looks similar, but it's screwed into the head.

Sender for the dashboard temperature gauge is nearby, it has a 1-wire connection.

 

Do I change the plugs or clean the plugs? What do I do?

 

First you figure out what's wrong. If a plug on the wiring harness is actually broken, you replace it. If it's simply dirty, then clean it. Broken wire? fix it. Get it?

If nothing visible, you can check the sensor. You should measure the sensor's resistance & compare against the chart of what the resistance is SUPPOSED to be.

Still no joy? You may have to check continuity of the wiring all the way back to the ECU. Judging from your questions, this may be a job for someone who's more comfortable with electrical troubleshooting.