Renix Distributor Indexing

Hello all,
I recently finished my custom front axle on my 1990 MJ, and she's not happy she sat for a few weeks. She's running a little rich, mileage first decreased from 18 to 15, and stayed at 15 for a long time. After the axle swap, she's down to 11-12, and smells rich. All my sensors are new and I JUST passed smog right before the swap, so I'm a little confused. However, it does feel slow and I've needed to reindex the distributor because I haven't done it yet, however I wanted to make certain of a few things:

1. I have a high altitude CPS, which should improve my MPG, but when I put it in, it actually went down. I noticed no performance increase. Is it because of a shitty CPS?

2. Can I index the distributor with the high altitude CPS, or should I order a stock one and use that?

The dizzy indexing and CPS are unrelated. Index it.

http://cruiser54.com/?p=68

First thing I'd do is cut a window in an old distributor, find TDC 1 and see how far off your rotor is. The ECU corrects timing, the problems start when you run out of advance (or retard), in effect the rotor position moves out of the envelope the ECU can correct. Side note, initial timing can be pretty far off, the ECU corrects over a pretty wide range

Just a wild guess but check your connectors for being oil soaked. They aren't sealed well and oil can seep in and mess with your sensor vales.

Recheck your vacuum lines.

No need to cut up a cap. Just use a sharpie to mark where the #1 cylinder is before removing the cap.

I rotate the engine to roughly 14 degrees BTDC and insert the distributor to where the rotor is pointing at the #1 position. The engine runs with around 14 degrees of minimum advance. That allows for any advance in the timing by the computer to still have the rotor close enough to the #1 plug wire to jump across and fire well.

Distributor indexing explained
For clarification though, that’s not a cam sensor inside the Renix dizzy. It’s there to fire the injectors sequentially with the firing order. You’ll never notice if it went bad because the ECU will try to “guess” where it is and does a heck of a job at it.

As for the “timing”, it is controlled by the ECU. Ever notice how wide the tip of the rotor is? Try and wrap your head around this:

When the ECU yells “Fire” to the ignition control module, where is the rotor in relationship to the dizzy terminal? Not to the terminal yet? Past the terminal too far?

What happens to the spark/secondary ignition strength when it has to jump the Grand Canyon in comparison to shooting from a rotor tip?

Tip 13 gets the thing right. Use Tip 12 first to guarantee you’re on #1 TDC.

I take it she was happy before the axle swap and ran fine???

If yes, then

You likely damaged the O2 sensor wiring to the O2 sensor, and or the O2 sensor doing the axle swap. What O2 sensor did you replace it with it???? The Renix uses only the old OEM style Bosch sensor, not the HO 91-01 sensors!!!! They are completely different.

What else did you do?????

http://www.naxja.org/forum/showthread.php?t=1012701&highlight=oxygen+sensor+testing

Changing the axle should have had no effect on the distributor.

Oh, and if the O2 sensor is not getting 12-14 volt power from the O2 sensor heater relay it will suck gas like a demon too.

Have you tested the O2 sensor, and other sensor grounds????

What axle/tire size did you swap to? That can kill fuel economy also.

Lastly, are you in a high altitude location? If not, put the right CPS sensor on it.

Francesco said:

Hello all,
I recently finished my custom front axle on my 1990 MJ, and she's not happy she sat for a few weeks. She's running a little rich, mileage first decreased from 18 to 15, and stayed at 15 for a long time. After the axle swap, she's down to 11-12, and smells rich. All my sensors are new and I JUST passed smog right before the swap, so I'm a little confused. However, it does feel slow and I've needed to reindex the distributor because I haven't done it yet, however I wanted to make certain of a few things:

1. I have a high altitude CPS, which should improve my MPG, but when I put it in, it actually went down. I noticed no performance increase. Is it because of a shitty CPS?

2. Can I index the distributor with the high altitude CPS, or should I order a stock one and use that?

Click to expand...