Ignition timing confusion

[AC439]

I had decided to check the timing on my 86LXi. So, I read the FSM 24-4 and 24-5 ten times, the Haynes manual ten times and several threads in this forum. I also googled to no avail.

Basically, I'm confused with the FSM. Step 3 says to disconnect the hoses from the vac advance, check for suction on the inner hose, then plug them. Afterwards, align the timing mark to the pointer (step 6 & 7). Then in step 8, it says to disconnect the outside and apply vacuum. But the outside hose has already been disconnected and plugged ! Then in step 9, it says to clam the hoses. So, somewhere along the line, there is a missing step in the FSM to reconnect the hoses to the vacuum advance !!!!!

From what I understand, most cars that have both mechanical and vacuum advance should set the base timing without the effect of the vacuum advance, that's why the base timing is set when the vacuum advance hose is disconnected and plugged. Then after the base timing is aligned (in my case 15 degree BTDC), reconnect the vacuum hose and the timing should advance above 15 degree BTDC.

From reading the Haynes manual, the procedure sounds different. It says to disconnect the hoses from off the vac advance, plug them and reconnect them to the vac advance. So, it sounds like I'm going to disconnect the hoses from the hoses from the small metal tubing side and plug them. I will then set the timing to 15 BTDC while hose #2 is sucking air !

I can tell the engine rpms are different when hose #2 is plugged or unplugged. So, what is the correct procedure ?

Also, I have noticed most folks here say to adjust the timing while the vacuum advance connected to the specified timing mark (15 BTDC for A/T and 20 BTDC for M/T).

- AC

[Oldblueaccord]

Well there is not much to it.

I would...

1. Verify the car is warmed up fully and the idle speed is set correctly

2. Either unhook and plug or pinch off the 2 lines to the distribtutor advance

3. Check the timing with a timing light and adjust as necessary.

Thats about it. I usually after all that verify with the timing light that the distributor does actually advance when the rpms go up and that the mark is nice and steady at idle. Since the bellhousing blocks the view of the mark off idle thats about all you can figure with out seeing how far the mark moves and at what RPM.

wp

[AC439]

Thanks for reply and that's pretty much what I did - warmed up, disconnected the two hoses and plug them then adjust the base timing (had to advance little bit to align the pointer to the middle of the 3 marks). After that, I verified that I have mechanical advance when I rev the engine. Also after I plugged back hose #2, the vacuum advance kicked in and the timing mark advanced beyond the visual window.

Road test is fine, I don't have any knocking. However, the engine seems to run slightly louder. Definitely due to the more advanced timing. I'm hoping the gas mileage would show an improvement.

-AC

[cygnus x-1]

I could be wrong about this but aren't there actually two sets of marks on the flywheel? One mark at 0 degrees and a few marks where the idle advance should be? I don't actually know anymore because I have a lightened flywheel and the marks were cut off. I had to paint on my own.

C|

[Oldblueaccord]

Yeah its the red mark I think I put mine on but its been a while since I have used the marks and not timed it more(advanced) by ear. Thats red mark on EFI cars I think.


wp

[AC439]

On my LXi, the marks are like as shown in the picture on the lower right corner of FSM page 24-4 (automatic). Mine has two shorter lines besides the long line which indicated +2 or -2 of 15 degrees BTDC like below (and the final configuration after I aligned it with vacuum advance disconnected and hoses plugged):-


...| | <----the base of the pointer
....V <----the pointer
... | <----the center line of the mark at 15 degree BTDC
.|1|5| <----the number indicates 15 degree BTDC and two side marks
indicating + 2 degrees and - 2 degrees.


So far, I don't have any pinging or knocking but definitely feel the engine runs slightly louder. I'm also running 1/2 a bottle of Seafoam this morning through the fuel tank (on half tank). I put 75 miles this morning and feel the car runs smoother but will be keeping my fingers crossed..........
- AC

[cygnus x-1]

Something about the engine being louder after adjusting the timing was bugging me so I dug out my service manual copy and looked it up. I did remember that there was something confusing about the directions for adjusting the timing but I couldn't remember exactly what. The part in step 3 where it says to "plug the hoses", I think should have been "reconnect the hoses" or "plug the hoses back into the distributor". The rest of procedure makes sense then.

From what you say below though it sounds like you have the timing set at 15 degrees BTDC with the vacuum advance disconnected. If that's the case I believe this is incorrect. You want it at 15 degrees BTDC with the vacuum advance connected. With the vacuum advance disconnected it should be at 4 degrees BTDC. There should be a white mark at (I think) 0 degrees.
EDIT: Step 9 in my FSM says that he timing should be 4 degrees with the vac advance disconnected.


I'm thinking it's running louder because the timing is too far advanced. I've done a lot of messing around with the timing on these engines and found that it's difficult to hear any pinging and that they seem to tolerate quite a lot of advance without complaining too much. So try setting the timing back 10 degrees or so from where it's at now and see if it runs better.

C|



On my LXi, the marks are like as shown in the picture on the lower right corner of FSM page 24-4 (automatic). Mine has two shorter lines besides the long line which indicated +2 or -2 of 15 degrees BTDC like below (and the final configuration after I aligned it with vacuum advance disconnected and hoses plugged):-


...| | <----the base of the pointer
....V <----the pointer
... | <----the center line of the mark at 15 degree BTDC
.|1|5| <----the number indicates 15 degree BTDC and two side marks
indicating + 2 degrees and - 2 degrees.


So far, I don't have any pinging or knocking but definitely feel the engine runs slightly louder. I'm also running 1/2 a bottle of Seafoam this morning through the fuel tank (on half tank). I put 75 miles this morning and feel the car runs smoother but will be keeping my fingers crossed..........
- AC

[2oodoor]

Something about the engine being louder after adjusting the timing was bugging me so I dug out my service manual copy and looked it up.
I'm thinking it's running louder because the timing is too far advanced. I've done a lot of messing around with the timing on these engines and found that it's difficult to hear any pinging and that they seem to tolerate quite a lot of advance without complaining too much. So try setting the timing back 10 degrees or so from where it's at now and see if it runs better.

C|

very interesting, I was trying to power tune that stock DX with the 38 on it and gave it gobs of advance, it made little objections to it but I did seem to loose a little grunt midrange. I need to put a light on it and put the header on it already. Im swapping that carb to the b20 asap anyway though.

[AC439]

Something about the engine being louder after adjusting the timing was bugging me so I dug out my service manual copy and looked it up. I did remember that there was something confusing about the directions for adjusting the timing but I couldn't remember exactly what. The part in step 3 where it says to "plug the hoses", I think should have been "reconnect the hoses" or "plug the hoses back into the distributor". The rest of procedure makes sense then.

From what you say below though it sounds like you have the timing set at 15 degrees BTDC with the vacuum advance disconnected. If that's the case I believe this is incorrect. You want it at 15 degrees BTDC with the vacuum advance connected. With the vacuum advance disconnected it should be at 4 degrees BTDC. There should be a white mark at (I think) 0 degrees.
EDIT: Step 9 in my FSM says that he timing should be 4 degrees with the vac advance disconnected.


I'm thinking it's running louder because the timing is too far advanced. I've done a lot of messing around with the timing on these engines and found that it's difficult to hear any pinging and that they seem to tolerate quite a lot of advance without complaining too much. So try setting the timing back 10 degrees or so from where it's at now and see if it runs better.

C|

I think you are right. I just re-read the FSM. Somewhere along the line, the FSM failed to say reconnect the vacuum hoses. The "reconnect hoses" step should be at the end of step 3 or at the beginning of step 4. The diagram in step 4 (the one with the timing light shown) shows the vacuum hoses connected. Then the rest of the procedure makes sense.

[AC439]

Ok, I retarded the timing by about 5 degrees. The car drives with less noise and feels more normal. I have put marks on the dizzy so I know if I screw up I can put it back to the way it was. Now, it is still a few degrees advance compare to where it was. I'm going to drive it for a few more days to test it out.

[Dr_Snooz]

Something about the engine being louder after adjusting the timing was bugging me so I dug out my service manual copy and looked it up. I did remember that there was something confusing about the directions for adjusting the timing but I couldn't remember exactly what. The part in step 3 where it says to "plug the hoses", I think should have been "reconnect the hoses" or "plug the hoses back into the distributor". The rest of procedure makes sense then.

From what you say below though it sounds like you have the timing set at 15 degrees BTDC with the vacuum advance disconnected. If that's the case I believe this is incorrect. You want it at 15 degrees BTDC with the vacuum advance connected. With the vacuum advance disconnected it should be at 4 degrees BTDC. There should be a white mark at (I think) 0 degrees.
EDIT: Step 9 in my FSM says that he timing should be 4 degrees with the vac advance disconnected.


I'm thinking it's running louder because the timing is too far advanced. I've done a lot of messing around with the timing on these engines and found that it's difficult to hear any pinging and that they seem to tolerate quite a lot of advance without complaining too much. So try setting the timing back 10 degrees or so from where it's at now and see if it runs better.

C|

Cygnus is right. Someone on here started a rumor that you needed to have the vacuum lines disconnected to set the timing...

...Okay it was I! Oh the shame!!

Anyway, the timing with the vacuum lines disconnected is 4 deg BTDC. I believe that coincides with the green circle on the AT flywheel. With the lines connected it's 15 deg.

I agree that the timing section in the manual is confusing. The reason is because it's so exhaustive. There is a lot that can go wrong there, so it's good to have it, but all you really need to know is that:

1. The vacuum advance pot holds vacuum (check with a vacuum pump)
2. The timing is 15 deg BTDC.

I know my pot holds vacuum, so I just throw the timing light on there, set it to 15 and go.

[AC439]

Actually, the Haynes manual says the same - to disconnect the vacuum hosts from the vac advance and set it to the value on the sticker under the engine hood. I thought for most cars that have a mechanical and vac advance, you do have to disconnect the vac hoses and set the base timing. Then reconnect the hoses to check vac advance. Apparently, our cars are different and the FSM is very confusing.

[cygnus x-1]

Actually, the Haynes manual says the same - to disconnect the vacuum hosts from the vac advance and set it to the value on the sticker under the engine hood. I thought for most cars that have a mechanical and vac advance, you do have to disconnect the vac hoses and set the base timing. Then reconnect the hoses to check vac advance. Apparently, our cars are different and the FSM is very confusing.


I would always disconnect the vac advance to adjust timing just in case the vac advance isn't working properly. That way you at least get the base timing correct. If your vac advance isn't advancing as far as it should you might end up setting the distributor too far ahead to make up for it.

So with vac advance disconnected set it to 4 degrees.
Plug in vac advance and check that it's at 15 degrees (or 20 for manual).
If it's not your vac advance is probably leaking (many do).

C|

[Dr_Snooz]

I would always disconnect the vac advance to adjust timing just in case the vac advance isn't working properly. That way you at least get the base timing correct. If your vac advance isn't advancing as far as it should you might end up setting the distributor too far ahead to make up for it.

So with vac advance disconnected set it to 4 degrees.
Plug in vac advance and check that it's at 15 degrees (or 20 for manual).
If it's not your vac advance is probably leaking (many do).

C|

If I knew where 4 deg BTDC was, I'd do it....