Renix CPS Advance Mod


The sensor portion of the CPS needs to slide up the perforated bar towards the top of the engine.

Mark the perforated bar’s top end with paint or marker.

Place the CPS in a vice,  just not quite clamping the bar, the sensor resting on the vice jaws, with the Top part protruding.

Place a bolt that fits tightly into the hole at the Top part of the bar.

With a hammer, tap the Top part of the bar and it will slide through the sensor portion of the CPS. Stop when the sensor portion is about 3/8″ from the edge of the bolt hole.

CPS advance mod

Revised 1-31-2016

29 thoughts on “Renix CPS Advance Mod”

  1. What are the exact benefits of this my cps is reading weak I got one from the parts store and wouldn’t you know it read only .2v not .5 so now I’m ordering one from the stealership for 75 bucks and 4 days shipping but it’s oem nos. I am going to try the 3/8 hole trick and clean my tip on my old stock one see if it works while I wait on the new one. But what does slidding it up more do. I know in combination with the bigger hole it will bring the tip closer to flywheel but anything else of so what exactly.

  2. I tried that with my old cps and it broke it die to how the bar is mounted threw the plastic with the holes does it only work with aftermarket ones

  3. I tried your advance mod with a brand new Standard brand CPS, but it wouldn’t budge at all and began to damage the metal, I stopped trying when I saw the metal begin to deform.

    1. That’s a first. Did you use a bolt in the hole that you were pounding on?
      I’ve been doing this procedure for 29 years with perfect success…..

  4. Max advance without pinging/knocking is ideal. Renix has a knock sensor that will tell the puter to retard timing if it knocks. The idea of this mod it so keep it as advanced as it can be for more power and better mileage. Trying it myself right now on a Standard #PC307

  5. It went pretty easy. Tim, Hawkeye, there IS something. I’ve been banging things to move for lots of years, there is a “feel”. I could have been “timid” with that thing all day and gotten nowhere but after a few “taps” I could feel it needed some firm persuasion. Any bounce of the backup is not OK. Backup’s gotta be rock solid. One or two more solid shots freed it, then I tapped it to about 3/8 inches from the hole.

    Not sure what would work for a guy without a large vice. Maybe a large crescent wrench laid over the hole in a Ford bumper where the tow ball goes, or a head port, something like that. Got to be rock solid.
    End of a receiver hitch?

  6. I’ve seen with a 87 or 90 engine module initial timing is 14 degrees and total timing is 39 degrees. When you advance the sensor what does initial and total timing change to. I’ve read that the knock sensor is suppose to influence timing but I have not seen it change on my scanner even when running the Mopar module that had 49 degrees total with the knock sensor throwing numbers so fast I could not read them.

    1. I think it only fools the ECU about 5 degrees or so. That’s how the knock sensor works. At 2000 RPM, you should see it bouncing around quickly at 20. I have no idea what the 20 stands for!! LOL.

  7. I did this mod along with enlarging the mount hole. At the same time I changed out my map sensor and o2 sensor. My idle went to about 1200 rpms. There are no vacuum leaks, TPS is set right and a new IAC. All grounds have been corrected. It’s a 89 waggy. Any ideas?

      1. One little thing I didn’t mention. I also went ahead and did the injector upgrade. I had 2 of the stock ones that were not closing and blew up a muffler. Rather violently I might add. I didn’t think the TPS had alot to do with idle speed. It runs good other wise. It did stall yesterday while driving at about 1700 rpms.

  8. Thanks for the responses. Great site. I have found vacuum leaks in weird areas ( bumper) and bad grounds all over. it kept dieing on me for no reason. Wiggled plugs below coil and it would die took it all apart and refreshed per your tips. Seems good now. Thanks again. I think I have idle issue under control. Adjusted stop to .003 but still just below 1000 in park and 950 or so in gear at temp.

  9. Mine shows a knock count of 60 under acceleration and you can feel the knocking. I am at 7000’ but I wouldn’t think that would be a problem. Any other suggestion?

    That’s strange. Sure it isn’t sensing some other knocking, like internals?

    1. Doesn’t feel like internal parts. Feels like ignition knock. I do know I have a couple of lifters that will bleed down if engine sits, but lifter noise is significantly different. This jeep came w second house we bought in mountains so working time is limited. Since you think it’s strange, I guess I will pull head to replace lifters and inspect everything else.

  10. Hi Cruiser54. I have an 87 4.0 renix running pretty good. I tried this advance and loved the quicker start and noticeably more power. But my idle is bad. It runs good then stalls and sometimes dies. I thought maybe i advanced too far so backed it off. I had to back off almost to stock position to get smooth idle. Is it just not going to work with my jeep or am i missing something? I would love to be able to enjoy this tip but have to have the idle. What are your thoughts?

  11. Yes I have indexed the distributor also removed the c101 and most other tips. After doing this mod i had to back it off alot just to get it to run. Then fought the idle issue for some time changing the iac and adjust the voltage on the tps before backing the cps back off a little more. It was running like that brand new renix on youtube with the gold valve cover, the cleanest one i have ever seen you know the one? haha. I also have a new o2 sensor and new exhaust manifold and i know the distributor is right on. I also just installed new refurbished volvo injectors.
    Thank you and let me know your thoughts?

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