My son's 91 civic with a regular 1.5 liter engine had some problems with oil leaks and leaking head gasket. A used engine dealer talked us into replacing the engine ( long and short block)with a used VTEC model as it has more torque and power. He claimed everything else could be retained from the old engine. Here is what's happening after the transplant. 1.\ Idle especially with a cold engine goes drrrttt-drrrttt-drrrttt-drrrttt, idle improves when the engine warms up, roughness sometimes even disappears .. 2.\ If I let go of the accelerator when going at any speed, engine RPM drops abruptly and feels like the engine is going to stall but it won't. 3.\ I noticed a green connector beside the distributor assembly but nothing is hooked to it. I asked the used engine dealer's mechanic what is it. He told me that the connector is supposed to be be hooked up to the computer, that without that being connected, the engine runs as a regular non-VTEC engine. Mechanic also told me that I will have to replace the engine management computer in order for the VTEC feature to function. We don't want to spend much and we can live without the VTEC feature but is there a way to make the engine run smoother? Comments please and thank you.
You need the ECU (engine control unit,or 'computer') from a VTEC car because thats what controls the VTEC function.The VTEC function is integral to that engine. The ECU also has the proper "map" for that engine.(proper fuel and ignition management at any particular RPM)
If by that you mean that the idle speed keeps fluctuating, then it could be a problem with the coolant. There is a fairly elaborate procedure for filling and bleeding the system on some Hondas. If you have air pockets trapped in the system, you can get fluctuating idle. Does the RPMs drop below normal idle speed and then bounce back up to normal, or are you just concerned about how quickly it drops down to idle?
I advise you to find out what type (example 1996 Honda Civic) of car the engine was removed from. Once you find out the information, visit a junk yard and buy a computer and hook it to the connector.
