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'97 GL wagon 3.0L: Replaced CMP Synchro OK, But it's slightly misaligned. Now what?

'97 GL wagon 3.0L: Replaced CMP Synchro OK, But it’s slightly misaligned. Now what?

200k miles. I marked the position of the synchro body OK, but since the “vane” was so mangled by the old magnet destoying it, I couldn’t be absolutely sure the “vane” on the new synchro ended up in the exact same position.

Obviously it’s NOT in the same position because, although the car starts and idles well enough, it lacks power and the Check Engine Light comes on throwing spark plug codes (which seem to change randomly from start-up to start-up).

I COULD just yank it out and turn the gear a tooth one way or the other, but is there a more precise way to do it? If I go to TDC, that’s STILL not going to tell me exactly where the “vane” needs to be (unless there’s a mark on the synchro body for TDC, which I doubt).

A new hamonic balancer.

A harmonic balancer is produced as a two piece unit in the first place. ( three when you add that trigger/pulse ring. )
With age and other damage like yours they begin to come apart.
You’ll never get it realigned correctly.

This is the tool used to properly position the CMP synchro.

Without it, it’s just a guessing game.



I appreciate your response, and I know about the tool, but I put this thing in as carefully as I could. I marked the synchro body to the block, so the synchro body went back in with the same orientation as the one that came out. This means the electrical connector is back in the same position as the old one (almost right up against that nearby huge silver fastener). It’s just the vane that’s off by a tooth, I’m guessing. What else could it be? The old one was mangled and flattened, and even though I could see its leading and trailing edges, it was still a bit of a guess as to exactly where the new vane would need to end up.

But before I order the tool - which may STILL not solve my problem because:

1.) I’ll have to locate TDC on #1 cylinder (not sure if I can precisely do this)

2.) Even if I’m successful with #1, then the electrical connector must end up at “33 degrees counterclockwise of the engine centerline” (How is THAT measured??). And how does the synchro install with the tool snapped on top? Doesn’t the tool stop the vane from rotating? Seems like I could conceivably end up in the same place … being off by a tooth.

When the car idles right now, you can smell gas (normally you cannot). This means the engine is running rich, correct? Can I just rotate the synchro body one way or the other to correct this? Or, if I DO have to pull the synchro out and move the bottom gear a tooth one way or the other, based on the engine running rich - should the vane end up MORE clockwise or LESS clockwise??? In other words, assuming the vane turns clockwise during normal operation (I think it does), should I reinsert so that the leading edge of the half-moon vane ends up at 6 o’clock (vs. 5 o’clock), or at 4 o’clock?

You can do this 2 ways…with a synchro alignment tool (sits on top of the synchro in place of the cmp sensor and follow the instructions of the tool. (OTC Tool) you’ll need TDC or you can use a 2 channel lab scope to sync the crank signal to the cmp signal by rotating the body of the synchroniser. Cmp goes high @ 26deg ATDC. I can send u a gif of this if you have the resources

I don’t have the 2 channel lab scope, but can I use a volt meter? Is it possible to read the crank sensor with a volt meter to find TDC on #1 cylinder (compression stroke) … instead of pulling the plugs, etc.

No…must have a lab scope…need to see the sine wave of the crank sensor (AC signal) and the square wave of the CMP Digital signal live and compare the two. The pattern need to align

Oh. If TDC of cylinder #1 (compression) is really that important, there should really be an easier way to find it than pulling the plugs and rotating the engine.

Reinstalled the synchro by finding TDC on #1 (compression), then setting the lower leading edge of the ‘half-moon’ vane to slightly before the centerline of where the sensor sits (I believe this is the correct location according to the orientation of the positioning tool), but something still not right. No more codes, no more Check Engine light (even after 30+ miles of driving), but it’s rough.

Could a strobe light be used to determine whether or not I’ve got my CMP synchro aligned properly? I’m looking for an easy way to verify what I’ve done without having to take anything apart.

Looks like I finally got it right earlier today. Turned out the TDC mark on the damper was 90-100 degrees off (@ 3 o’clock) … for whatever reason (bad harmonic balancer???). Last weekend, believing I had simply over-turned the crank, I was rolling it back 90 degrees to line up the damper groove with the cast iron TDC pointer on the block. This was proper procedure, but apparently wrong for this car. Today, after seeing the same thing again, I decided to just leave the crank TDC mark where it was (@ about 3 o’clock) and set the synchro to that. Took me 3 or 4 tries and I had the vane in the correct position! I could tell as soon as I started the engine that it was much better this time (quieter). Took it out for a 15 miles drive and no Check Engine light. I also installed all new (properly gapped) plugs and wires, although I have to say that I really couldn’t feel any difference in pep, pickup, or power from the 200,000+ mile plugs and wires that were in there since the car was built in '97!

So two things learned here:

1.) You can’t always go by the TDC pointer on the block. This car has over 200,000 miles on it and apparently TDC has shifted by 90 degrees (is this a bad harmonic balancer?)

2.) You can mis-install the CMP Synchro, have the car run rough, and still NOT get a Check Engine light!

Next order of business with this car is a metallic screeching at the serpentine belt area. I sprayed water on the belt itself (the vertical stretch that runs parallel to the firewall) and the noise quieted. But I also sprayed water on the alternator pulley with the same result! In fact, I could spray water on ANY pulley and quiet the noise. It’s the original alternator and power steering pump, so either of those pulleys could be causing the noise. Serp belt, water pump and idler pulley bearing are about 4 years old. Guess I need to remove the belt first and start spinning the pulleys (listening/feeling for problems)? When I was turning the engine by hand there was a pinching rubber sound from the serp belt as it rotated. Is this a clue, or is this normal?

Migh also have a head gasket leak. Need to perform a pressure test of some kind to see if I can get air or liquid to come out the side of the block.

Try replacing the belt and the belt tensioner idler bearing. If you think you have a head gasket leak, you can do a compression test. Are you loosing antifreeze? Is there oil/sludge in your antifreeze?


No oil in the antifreeze that I can see. I THINK the antifreeze is being consumed by the engine in very small amounts because I DO loose antifreeze over time. I’ve had leaks in the “H” hose and degas tank, but those were fixed. Plus, the water pump was replaced when I suspected rotted impellers (which turned out to be true, but only barely). I’m going to pull the serpentine belt off and check all the pulleys. It’ll be funny if it’s the idler bearing AGAIN! I think I changed that out about 4 years ago (I’d have to check my records).

ken green:

You were saying I’d never get “it” realigned correctly. Were you talking about the harmonic balancer (or the synchro)? How much trouble is it to replace the harmonic balancer? I think my front cover has a leak, too, so maybe it gets replaced along with that (and the oil pan gasket)?