Timing chain alignment problem

T

The shuggs

TJ Enthusiast
Joined
Jun 14, 2019
Messages
151
Location
Edmonton, Alberta
I'm replacing my worn timing chain, and I noticed an oddity, the timing marks aligned one revolution after TDC. So I attempted to fix that, but couldn't get the roll pin on the cam shaft out so that I could put it in the other hole. Defeated, I started to put everything back on. That's when I noticed that when the timing marks on the gears were aligned, the rotor pointed a little bit after the pickup on the cap. I set the cam gear back one link on the chain and the rotor points right at the pickup.

Does the rotor need to be pointing exactly at the pickup, or should I be strictly following the timing marks?
20190903_211859.jpg

Timing marks off by 1 link/tooth.
20190903_211948.jpg

Another angle.
20190903_212043.jpg


Rotor pointing right at the #4 pickup (not the #1 because roll pin for the gear is 180 degrees off).
 
If it were my project I would align the marks they time the camshaft to the crankshaft. Then worry about the distributor which is ignition timing
 
That's what I was leaning towards, I'm just overthinking everything because I'm trying to fix a persistent timing issue. The engine will start up fine, but will run rough until it fully warms up. I've replaced the TPS, IAT, CMP, CKP, plugs, rotor, cap, and wires. I was able to get some live data that showed the crank, and cam constantly trying to readjust, so I figured it was the timing chain preventing them from syncing.
 
Keep the timing chain in the right place. Easy enough to adjust the distributor for spark timing after. The spark can jump across easily when just the corners of the rotor and cap align.
 
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1/2" (I think) to the engine block. Loosen and twist. Or do you mean the computer controls spark advance? If so then why worry if the rotor is a bit off?
 
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So I replaced the timing chain, and had no issues for 3 weeks/500km, then as soon as the temperatures dipped, the problem came back. :mad:

I suspect the new timing chain brought everything closer together in terms of timing enough that the computer was able to adjust the timing, however the problem was still there and now that it's colder, it's gotten worse.

Would a dying ignition coil cause this? Inconsistent spark making the PCM think that the CMP is off?
 
Bad coil can cause a miss especially at higher rpms. And as they get hotter the performance gets worse. Spend the money on a good one. Those "chrome" ones hanging behind the parts counter for $20 are shit. Wouldn't even use them on a tractor. Get a good name brand with a high output.
 
You know the distributor can go bad too. I'm not up on the TJ distributors, but most have vacuum and springs that work the advance. And either of them can go bad too. I've seen broken springs get into the lower assy. and lock up all advance, or stretch and give full advance just off idle.
 
My situation is kind of the opposite, it runs rough for the first 10 minutes after a cold start. It won't even accelerate. After that it will work fine as long as it doesn't cool down completely. I'll still replace the coil, but I'm quite lost on this one.

All timing adjustments are made by the PCM, there's no play in my distributor shaft, and past the coil the electrical parts are new. In the graphs the CMP looks good except the PCM is hunting for the correct timing.
 
Is it possible a sensor somewhere is sending bad info to the computer? I think the computer uses a different set of parameters for a "cold" engine versus a "hot" engine. The O2 sensors are not used when cold, and who knows what else is interpreted differently. You might search or start a new post for computer startup problems.
 
Not sure if u got sorted. Try manifold air temp sensor? Also I've replaced my chain and timing is off when checked with light cant figure it out
 
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