I chipped my ECU, and installed it today with the J1 jumper still in place. It idled like I had a vacuum leak (revs jump up, then down, then up, then down). I removed the jumper, and now it idles closer to a stock idle, but it does the same thing. No CEL.

The car is a '99 Civic Si, LS/VTEC, currently have a VAFC hooked up. The ECU is a P28 out of a '95 Civic EX 1.6L VTEC.

Anyone have any suggestions?

 

Update. I just pulled the chip completely out of the socket, kept the J1 jumper pulled, and now it idles like normal, but occasionally it will do the revving thing again.

Keep in mind, the chip I had in there is completely blank. NO information has been burned on it yet. Think this could be the cause?

 

with J1 in place and a blank chip in the socket... you expected it to run correctly?

put something on that chip and see what happens.

BTW it's a wonder the P28 maps idled your engine, get the right maps in there.

 

Yeah, to be honest I know nothing about OBD1 ecu's, nor what's on them.. so I figured I'd test it out. I just wanted to make sure my hunch was right. I'll put something on the chip as soon as I find a chip burner. I'll update in a couple of days. Thanks.