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[Fwd: Ignition timing question...?]

This should initiate some good debate...

I've always understood that ignition timing should be set with any advance systems (vacuum diaphragm, etc.) disconnected. I tried to set up my '87 Accord that way, and I can't get anywhere near the 20-degree timing mark with the vacuum advance disonnected. Leaving the vacuum line attached, it jumps right close to the 2-degree mark and seems to run well, if missing a little "jump". Oddly enough, when I accidentally took a test drive while forgetting to reconnect the vacuum line, it seem to have a lot better pick-up when I punched the gas...

Anyway, I'm looking in the shop manual... the directions say to disconnect, test, and then plug the vacuum lines, then goes on to list the proper timing settings for various engine/transmission setups, never specifying that one should reconnect the vacuum lines, and describes how to adjust the timing by twisting the distributor. So far so good...

BUT... all the diagrams show the vacuum lines still attached... AND the next step tells how to check the cold-advance operation (on engines that have it), while the following step THEN tells you to disconnect the vacuum hose(s), plug them, and then check the timing with an advance meter, listing way lower advance settings than the previous chart.

Example: the first chart

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shows that the A20A2s should be anywhere from 10+/-2 to 20+/-2 degrees (depending on variant and transmission) - it doesn't specifically say the advance lines should or shouldn't be connected, but you see in an earlier step that they have been disconnected and not reconnected. Meanwhile, the subsequent step
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says after disconnecting and plugging the hoses, all A20A2s should be 4 degrees.

So what's the story? Experience indicates that timing should be checked and set to 20 degrees (there's an actual "20-degree" mark on the flywheel) WITH the main advance line connected. Old-school knowledge, however, suggests that the line should be disconnected and plugged, but when I do that, it's impossible to get anywhere near 20 degrees (and really, old-school knowledge suggests that 20 degrees BTDC is an

*insane* amount of advance for ANY engine).

I've seen this topic generate a lot of debate on a couple boards over which is the proper procedure... just wondering what the concensus is in these parts?

Reply to
Matt Ion
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matt, if the honda factory manual says disconnect, then you disconnect. end of story. and who are you to judge 20 degrees? you've got two vacuum diaphragms iirc, both affect timing when connected, and their subsequent movement produces the correct result for that engine. it's real simple.

Reply to
jim beam

The thing is, the manual contradicts itself. If you actually follow the steps in order, it's got you disconnecting the hoses twice (and btw, only one is normally used, the other operates only when the engine is cold), and it's got two different advance settings, one saying for the A20A2 it should be 10, 15 or 20 degrees depending on the exact variant, the other saying it should be 4 degrees for all A20A2s.

Reply to
Matt Ion

which manual is that matt?

Reply to
jim beam

The instruction to set the timing ended on step 7. If you go past step 7 you are in the section on testing the vacuum advance diaphragm and distributor advance mechanism and is not relevant to setting the timing.

First, Jim *did not* asked an obtuse question since many of us use a variety of factory service manual for a variety of year models.

For a bitter, hebetudinous guy that wants free advice I don't know why I'm answering this question. Secondly, cross-post correctly.

Reply to
Burt S.

Fine then. Is the timing set with the advance hose attached, or not? The procedure up to step 7 would suggest no - the hose is disconnected and plugged, and the timing set according to the chart. So you end up at 20 degrees with the hose detached.

So if you go on testing, you're once again disconnected the hoses, but now the timing is supposed to read four degrees?

Bitter? Sure. I ask a simple question, and all I get back are two posts suggesting I'm an idiot who can't read.

Yeah, well, that was a typo the first time so I had to repost to the second group separately.

Reply to
Matt Ion

You obviously miss the point on step 3 that you are *not* suppose to leave the hoses unplugged. A mechanic would unplug the hoses, put his/her index finger over them and reinsert (plugged) them to their original locations in a spit second. Yes, the hoses are supposed to be attached.

You are in the section on testing the vacuum advance diaphragm and distributor advance mechanism and is not relevant to setting the timing.

Reply to
Burt S.

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