Technical Backfire after timing adjustment

[Hharbers]

Bought strobo timing lamp to check timing of my 1987 pandan 4x4.
Car was running fine but wanted to be able to check timing

Timing mark (line on flywheel) was on 15 degrees instead 2 Degrees!
I adjusted it to 2 degrees according to my manual and made test drive.
When lifting throttle and light braking brake i have a lot of backfire./ Decelpop.
No big bangs but lot of popping sound in back muffler

How did i do it:
Warmed up engine to 90 degrees
Disconnected hose from advancing thing on ignition module
Put smal bolt in hose to plug it
Connected timing lamp to battery and pick up to most left sparkplug wire
Loosened bolts and rotaded module til timing was on 2 degrees and tighted module again.

What did i wrong?
Should i also plug of the nozzle of the advance unit also ?
Did i look at wrong timing mark at flywheel ?

 

[bugsymike]

Bought strobo timing lamp to check timing of my 1987 pandan 4x4.
Car was running fine but wanted to be able to check timing

Timing mark (line on flywheel) was on 15 degrees instead 2 Degrees!
I adjusted it to 2 degrees according to my manual and made test drive.
When lifting throttle and light braking brake i have a lot of backfire./ Decelpop.
No big bangs but lot of popping sound in back muffler

How did i do it:
Warmed up engine to 90 degrees
Disconnected hose from advancing thing on ignition module
Put smal bolt in hose to plug it
Connected timing lamp to battery and pick up to most left sparkplug wire
Loosened bolts and rotaded module til timing was on 2 degrees and tighted module again.

What did i wrong?
Should i also plug of the nozzle of the advance unit also ?
Did i look at wrong timing mark at flywheel ?

From memory checking timing through square hole in bell housing under rubber plug the timing marks on the casing are 0, 5, and 10 degrees.
Before fuel quality went down most ran happily at roughly 7 degrees, but a road test is always wise to be sure.
Is your idle speed too high, so mechanical advance kicking in?
I assume a basic timing light , not one where you can alter advance figures.
Details in columns above pen in photo.

 

[Hharbers]

From memory checking timing through square hole in bell housing under rubber plug the timing marks on the casing are 0, 5, and 10 degrees.
Before fuel quality went down most ran happily at roughly 7 degrees, but a road test is always wise to be sure.
Is your idle speed too high, so mechanical advance kicking in?
I assume a basic timing light , not one where you can alter advance figures.
Details in columns above pen in photo

Your correct time hole n bell housing is marked with 0-5-10-15 markings
I have just basic strobe gun

When i first checked it was at 15 degrees when idling (hot engine)
I didnt check idle rpm as i dont have a meter for it. will look tomorrow

in photo I read correct timing at 2 degrees +/- 2 degrees

Is it possible caused by belt timing
If it is 1 tooth off timing ?

 

[bugsymike]

Your correct time hole n bell housing is marked with 0-5-10-15 markings
I have just basic strobe gun

When i first checked it was at 15 degrees when idling (hot engine)
I didnt check idle rpm as i dont have a meter for it. will look tomorrow

in photo I read correct timing at 2 degrees +/- 2 degrees

Is it possible caused by belt timing
If it is 1 tooth off timing ?

Unlikely as engine would have been running poorly because of that before you altered the ignition timing, if that was the case.

 

[Hharbers]

Unlikely as engine would have been running poorly because of that before you altered the ignition timing, if that was the case.

You have a point. Was running fine before.

Timing should be 2 degrees at 850rpm
Dont know how to check rpm but i will figure it out

On line 28 of book at row of my 1987 4x4 engine 156a300 looks like marked that it should be measured with advance
I did it without the advance vacuüm hose connected

 

[bugsymike]

You have a point. Was running fine before.

Timing should be 2 degrees at 850rpm
Dont know how to check rpm but i will figure it out

On line 28 of book at row of my 1987 4x4 engine 156a300 looks like marked that it should be measured with advance
I did it without the advance vacuüm hose connected

Generally if tick over low then vacuum advance has little effect on most vehicles.
With yours electronically controlled I would put it back where it was initially if it ran happily like that.

 

[Hharbers]

Have put timing back to were it initially was and did some test driving but still same popping.
Seems when driving with bit of choke on decel popping is less.

I feel with my finger quite strong vacuum suction on hose to the carburateur on stationaire rpm

When i close hose end fully with my finger engine stalles almost.
When i put hose back on ignition module it runs normal stationary.

Is it possible it has something to do with other work i did last week and didnt drive after

new rear silencer but connection is not fully tight , leaks a bit exhaust gas

replaced clutch and have worked a lot in engine bay. Maybe disturbed something accidentally?
Vacuüm hose was pulled of carburateur and bit ripped at the end but i cut bit of and put it back on carb nipple

 

[bugsymike]

Any vacuum /air leak will affect/weaken the fuel mixture and cause backfiring, also air leaks on the exhaust, particularly on the over run down hills.

 

[Hharbers]

Just put a hose on the vacuum advance unit and noticed i can freely suck and blow in it. Looks like diafragm is broken so it doesnt react on vacuum

 

[bugsymike]

Just put a hose on the vacuum advance unit and noticed i can freely suck and blow in it. Looks like diafragm is broken so it doesnt react on vacuum

Sounds like diaphragm gone , so new vacuum advance unit, it won't help the problem, but may not be the total answer.