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Rotor won't line up with distributor mark

5K views 9 replies 5 participants last post by  lindburly 
#1 ·
I'm hoping someone has some insight on this -- it's got me stymied and very worried.

I recently bought a 99 Astro with 150,000 miles on it thinking I'd fix it up for my son to use as a work truck. It had a random misfire when I bought it, but after I replaced plugs, wires, distributor and rotor it ran smoothly. Next I replaced the lower intake manifold gasket, water pump, and thermostat.

Every time I try to reinstall the distributor with #1 cylinder at top dead center on the compression stroke, the distributor rotor refuses to line up with the number 6 on the distributor cap. It either sits slightly in advance of the 6 or quite a bit after of it (see photos). I've retried this installation at least 25 times hoping that I just didn't catch the right cog, and I'm absolutely certain that there is no intermediate cog that would put it in the correct position. It starts right up, but runs rough (like a misfire) in either of the two positions. I drove it down to O'Reilly's to scan the codes and it ran really badly with little power and made clanking noises (hopefully not rod knock). The scan showed a P1345 crankshaft position/camshaft position correlation error.

The gears at the bottom of the distributor do not appear to be worn and there is about 1.5 mm vertical play in it, which is within spec. I had my wife watch for distributor rotor movement while I moved the crank back and forth to check for timing chain slack. The amount of movement before turning the rotor is about 1/2 inch -- which calculates out to about 10 degrees. I'm about to bring it into a shop for further analysis. Have any of you run into this type of issue with your vehicles or have any ideas?
 

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#4 ·
Thanks for the suggestions, guys.

Yes, I do adjust the oil pump each time I try a different cog. I've found that the perfect tool for doing that is the car jack extension cause it's long with a screwdriver-type tip and no handle to interfere with your sight line. And I do turn the crank to TDC on the #1 cyl. compression stroke -- the rotor position is always as shown in the photos. I've viewed every how-to out there and, like I said, I've redone this at least 25 times and I always get the same result.

I'm looking at the distributor gear again and I guess I do see some wear on one side of each tooth. The worn sides look a little bit striated and rough and there is a tiny bit of erosion. It's hard to see how it could have much effect on the timing, though (attached a photo). I suppose the cam shaft teeth could also be worn or something.

So, in your experience, should the rotor be exactly in line with the 6 or is it sometimes off by a quarter of an inch or so? I read somewhere too about some shops expanding the hole in the distributor clamp to make it adjustable.
 

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#5 ·
I had similar trouble when putting in a new distributor. Had the marks lined up perfect per the book but ran terrible including the P1345 code. After multiple tries I found a position that ran good but the marks on the distributor where off quite a bit. I used a Tech2 scanner to verify that timing was correct. It was in spec even though the marks were off. Used the scanner to dial it right to zero per this video.


Runs great with good mpg. Maybe my oil pump gear is worn or chain is worn. It's an antique system so I'm not too hung up on the marks being off since the scanner reports it is right on.

My old distributor had the gear teeth worn down to a knife edge but it still ran good. Replaced it since I had everything apart anyway.
 
#6 ·
Thanks for the encouraging info! Did you cut a slot in your distributor clamp to adjust the cam retard? I don't have an analyzer to read the cam retard so I'll have to bring it in somewhere. The problem is without a slot in the distributor clamp, I don't think they'll be able to adjust it. I guess I'd be surprised if a dealer or service shop would cut into it to create a slot.
 
#7 ·
I did make a custom clamp with a slot in it to experiment with but it turns out it was not needed in the end. There was enough slop in the stock clamp for fine tuning to get things right to zero. Even without the fine tuning I was within a couple of degrees just like in the video, which is within spec and was running fine. The fine tuning to get the last couple of degrees to zero made no perceptible difference in the way it ran.

I would just very methodically move the gear one tooth at a time until you find a position that runs good. That is likely to be the correct timing. When I was one tooth off (retarded) the van would start and run pretty good but power was low. One more tooth advanced and everything felt right. If you find a position where everything seems to be working right then it likely is right. It was nice to have the scanner for confirmation but you can probably get there without it. One tooth off either way was obviously wrong even without the scanner.

The teeth on your gear don't look too bad to me. My old gear was far worse and still ran good. It is possible to replace just the gear rather than the whole distributor. I had vertical play in addition to gear wear so I replaced the whole thing.
 
#8 ·
Thanks -- that's VERY helpful. I'll keep experimenting and let you know how it goes.

I pulled wires sequentially from the distributor today to see if the misfire changed. It ran worse after pulling each wire except #3 so I'll test for spark and fuel there tomorrow. Pretty sure the spark will be ok, but I'm wondering if I could have gotten some dirt in the fuel line that could have clogged the #3 poppet. I'll sniff around and see if I can smell whether gas is getting into the cylinder.
 
#10 ·
This is just an update in case my experience can help anyone with similar problems. I eliminated the misfire by installing the updated multi-port spider. That old spider was really bad -- removing it was difficult as several of the little plastic squeeze clamps broke off in my hands.

I replaced the timing chain as it had a lot of slack, and I thought it might have skipped a tooth. It had not, but it was very loose. The engine was also making a ringing at certain RPMs that sounded like chain rubbing on metal. I did find out something that might be useful to others doing a timing chain job -- you don't need to drop the oil pan if you use a rasp to trim off just enough of the flange at the corners of the cover to allow it to be inserted over the oil pan gasket. I took off a little bit at a time and kept testing until I was able to do a dry fit. No oil leaks so far.

LOL, after changing it I found that with the tighter chain, the rotor was even farther in advance of the 6 on the distributor with the engine at TDC on #1 compression stroke when it was on it's closest distributor tooth to the mark. And it would idle, but soon cough to a halt in that position. Moving the distributor to the next cog brought it to a position that was quite a bit past the 6 on the distributor, but it ran. The
P1345 remained on and it made a lot of knocking noise when running at speed under load. I finally went to work on the distributor clamp hole, widening it by about 3/8" in the downward direction, so that rotor position that was formerly in advance of the #6 was now spot-on. The P1345 immediately went away and it runs good except that the ringing noise is still there at certain RPM and there is still some knocking noise under load -- but not in neutral (balance shaft??).
 
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