pulling hair out over dist indexing.

89xj 5speed 4.0

After a half hour search on here I've been messing with this for an hour or so and need a little help from you guys.My motor is felling kinda sluggish on accel.

TDC on number one compression stroke my rotor looks like this:
(thanks xj trail rider for the pic)



It should look like this,no???


For the life of me I can only get the rotor to set just before or just after #one.What gives???
Should I cut the tab off the dist as some others on here have done?

when you seat it do you first turn the rotor to the four o'clock position then slide it untill it seats? And ensure the oil pump is in the 11 o'clock position?

Yea it runs decent but lacks little.I'm thinking that the fuel syncronization is off by about 10degrees causing my acceleration lag.

Yep its on #one compression stroke.

is the rotor supposed to be sitting alittle past #one on the dist(first pic)or centered on it like in the second pic?

you want a small amount of advance to give the spark time kernel time to expand, so I would say slightly after the #1 terminal. I was under the impression that the cam sync sensor would compensate for any minor variances, but if there's a noticable difference between the two, I'd say the first pic is closer to correct.

came inside to take alittle break......the only way I can get the rotor to sit like in the second pic is to instal the dist while the motor is on the exhaust stroke,won't start that way at all.

Shorty said:

I'd say the first pic is closer to correct.

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now I'd really say the first sounds better!!:yelclap:

no doubt......

well I reinstalled the dist how it was in the first place(as pictured in the first pic)it runs as it always has.It seems like it is slow to wind up.

I need a little more info regarding cutting the tab off the dist so it will be adjustable.How does being able to turn the dist affect injector timing....or fuel syncronization as it is also know?
I'm under the impression that turning the dist has no affect on ignition timing because any adjustment you make the computer over rules,correct?

Oh and,I sorta remember a controversy over the factory not indexing distributors correctly....can someone elaborate on that as well?
One last question at the risk of sounding like a total newbie:What does detonation or spark knock sound like?Does it only happen under acceleration?
TIA.

outlander said:

well I reinstalled the dist how it was in the first place(as pictured in the first pic)it runs as it always has.It seems like it is slow to wind up.

I need a little more info regarding cutting the tab off the dist so it will be adjustable.How does being able to turn the dist affect injector timing....or fuel syncronization as it is also know?
I'm under the impression that turning the dist has no affect on ignition timing because any adjustment you make the computer over rules,correct?

Oh and,I sorta remember a controversy over the factory not indexing distributors correctly....can someone elaborate on that as well?
One last question at the risk of sounding like a total newbie:What does detonation or spark knock sound like?Does it only happen under acceleration?
TIA.

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I have heard that Renix era distributors can benefit from adjusting, because although the basic ignition timing is set by the computer, the rotor timing to the cap is not. I doubt that a change in injection timing would be significant. Unless the XJ violates the usual method of electronic injection, it injects just before the valve opens, so advancing it will not improve anything.

I have never fussed with this, but remember long ago on the old Jeep forum that someone suggested taking an old distributor cap and cutting a hole in it, then using that as a visual indicator of how far to move the distributor body to achieve better rotor-to-post timing.

As far as actual distributor-tooth-to-camshaft indexing, if your Jeep starts well and runs, you're pretty certain to have it right. When I played with my 87, I found that one tooth advanced caused hard starting but decent running, and one tooth retarded caused easy starting and no ability to get off idle.

I pretty much decided to leave well enough alone because I'm sick of fawking with it.....what a wasted day!!!

damn wish i would have caught this when it started. Ive already went through this when building my new motor. It dosent matter. The cam sensor will adjust it all back to the same place. I have moved one tooth forward and one back all over the damn place still runs the exact same. So end result........ get it close....... set it and forget it. *Ronco is a registered trade mark*

hahaha....I used to hate those infomercials,but oddly enough I would sometimes find myself sitting through them.uke:

thanks for the input,gentlemen.

cant find notes to set distributor right now
oil pump drive set to 11 o'clock if i rember correctly
reset mine the firing order was advanced 60 degrees on the cap

I have heard that Renix era distributors can benefit from adjusting, because although the basic ignition timing is set by the computer, the rotor timing to the cap is not.....
I have never fussed with this, but remember long ago on the old Jeep forum that someone suggested taking an old distributor cap and cutting a hole in it, then using that as a visual indicator of how far to move the distributor body to achieve better rotor-to-post timing.

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That must be why they like to go through caps and rotors so frequently? So am I to assume that you are supposed to use a timing light aimed at the hole in the cap? If so, am I also to assume that dead center of the post is what you would want to try for?

88 Wagonman said:

That must be why they like to go through caps and rotors so frequently? So am I to assume that you are supposed to use a timing light aimed at the hole in the cap? If so, am I also to assume that dead center of the post is what you would want to try for?

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My recollection is that people were doing it statically, just to bring it into better proximity to the post, but a timing light should do it too if you make the hole in the right place, and that would allow you to get the best position for the whole advance range. But my guess is that because there's such a wide contact area on the rotor, precision is not really necessary. I repeat the disclaimer though: I never tried it myself.

Changing the advance or retarding the timing really won't do much for a Renix. The computer is going to adjust. I've had mine a tooth off both directions (on numerous Renix motors) and they ran OK. Some Renix motors seem a bit more finicky than others, but most all can be a tooth off and run, they self adjust back to operating range.
Indexing the distributor was first introduced for a portion of the 87 model year (I got a TSB in the mail in late 88 or so along with an O2 senor recall for my 87). Some of the cam grinds (drive gear) were a bit off. The result was the motor could run out of retard (or was it advance) at certain RPM's and vacuum conditions. The indexing was to move the rotor a bit more towards the center of the spark advance/retard envelope.
Some after market cams produced the same results and re indexing the distributor was recommended.
It seems to also be beneficial on occasion if the distributor drive gears or timing chain parts are seriously worn.
The first indication of the motor running out of timing range is bucking, but this can also be from from a lean burn condition, it's not often a timing problem.
98 times out of a 100 the problem isn't timing, it's another sensor that has timing input or air/fuel ratio input. Or a mechanical problem.

Just for general info, advance doesn't equal power, you actually get better torque during high load/low vacuum conditions when the timing is retarded (closer to "0" or very little advance), in most street engines. Advancing the timing doesn't usually pay dividends till way high in the RPM band.
Somebody mentioned turning the static timing to 12 degrees and centering the rotor on number one at the cap, if I understood correctly. Seems reasonable, but I've never tried it.

Somebody really should to a pictorial on installing a Renix distributor. I'll post something up in a month or so when it warms up enough here to mess with it. Unless somebody beats me to it.

good idea

In the Renix era, there were some xj's that came off the assemblely line with the distriburor intalled one tooth off. If you can lay your hands on a yellow shop manual for 87, there is a bulletan bound in the back showing how to index the distributor.

Ron Hyslop said:

In the Renix era, there were some xj's that came off the assemblely line with the distriburor intalled one tooth off. If you can lay your hands on a yellow shop manual for 87, there is a bulletan bound in the back showing how to index the distributor.

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That's very interesting. My 87 was a hard starter for most of the time I had it, and finally got critical, acting as if it had hydrolocked. I replaced the distributor with one from an 89, making sure that it was indexed exactly as before, and the problem persisted. It turned out to be one tooth off, and I had wondered for a long time if it had always been that way.