Marine1Texas

I know this is bring up old thread. I have a 87 and followed the Renix tips from cruiser. I replaced the computer, every sensor, dizzy, took out the 101 connector and wired straight up, and still get rough idle. I tried 3 different computers, and even rewired one by one every wire. I put new cap and rotor with brass terminals, Champion copper NGK plugs and Belden ignition wires. Still rough idle. I bought a HEI and dropped it in and smooth idle on 1st start. The only problem I had was vacuum advance since there is no right place to connect it. I drove it around with advance off and it was amazing. Only suffer 2 mpg. For me it seemed to fix the problem however I would like to have the Renix ignition system working right. 3 months ago I took out the 4.0 and rebuilt it from bottom up. Replaced everything and every sensor again. I did not hook up the HEI and stuck with the renix. Rough idle on newly rebuilt motor still. Now when I say rough idle it does not shake or anything like that. When it starts from cold it idles around 955 to 1025 rpms for warmup time about 75 secs. Then it gos down to 560 to 815 rpms. it will go up and down from 560 to 815 all day long. It does not bog down on start off or die. It never bogs even when I stomp on it. Just that damn idle is bothering me. Since here in Texas my truck is exempt and only needs to pass visual I have done some mods. It has improved idle a bit. Mods are the cruiser advance timing, spectra intake air filter. Straight exhaust with high flow cat. I may try the HEI again if I can not find what the problem is.