backfires and dies at sops... and choppy when driving

[converted_to_datsun]

I'm aving trouble... prettymuch as soon as i fix something there's another problem. I set my timing yesterday and now it backfires on decell. it dies at stops and during acceleration or even at cruise it accels and decels. it seems like the "normal" acceleration is bogged down in the first place and for a fraction of a secone i get a pull of actual power.

 

the timing is almost spot on... it ran better before tho. should i adjust timing again? what the hell is wrong?

[converted_to_datsun]

oh and it's a 1979 with a l20b

[darrel]

If it ran great before you set the timing to "spec" set it back. Then check your crank pulley. It might be separating causing the timing mark to move. I have ran into that with z and zx crank pulleys.

[metalmonkey47]

Advance your timing!

 

Timing retarded too many degrees will cause all kinds of problems. How did you set it? With a timing light?

[converted_to_datsun]

timing was set with a timing light... but i figured out it was out 180 degrees so i have to do the timing and tuneing again. good news if it has more power with it put back right even though timng is way off now. probably going to put a new cap and wires on while i'm at it haha everything else is new... it's getting to the point where almost everything attached to the motor is brand new or rebuilt

[datzenmike]

Just in case the idle is too high and there is ported vacuum advance where there shouldn't be, remove the hose to the vacuum advance on the dizzy and check/set the timing again. Base or static timing HAS to be set without vacuum advance interfering with it. Check your mechanical advance too. If it's stuck slightly advanced, the static timing will be set incorrectly.

 

Best thing is to borrow a distributor to eliminate all these things that could be wrong on yours and figure out what's wrong.

[converted_to_datsun]

the closest datson to me has an early z 8 plug motor so i can't borrow.

 

but i can try timing without the vacume. before i set it before it was full advance and not it's retarded so hopefully i get it figured out today

[Rustina 510]

Losen the distributor and adjust it with the car idling, my wagon had the same issue until jake and I made some adjustments to it.

 

It didn't even need timing adjustment in my car so maybe it's the same for your l20

[datzenmike]

There should be no vacuum advance present at idle if everything working properly. But if the idle is set too high there may be some in the ported vacuum hose, so yeah pull hose off and see if timing drops and without it, re-set the timing to 12 degrees.

 

BTW backfiring (the odd pop) on deceleration is usually normal some of the time.

[converted_to_datsun]

Apparently it was misfireing. i replaced the cap and rotor and put new wires on and it's doing better but still need to retune it

[datzenmike]

Spark will always look for the easiest path to ground. Always. Could even be down another wire and fire a plug not on a compression stroke.

[converted_to_datsun]

Well i got shocked a couple times through the boot on my wires so that was a sure sign. I just got my manual in the mail yesterday and it looks like my vacume lines aren't even going to the right places in some cases or are missing where they shouldn't be. it's going to be a long process orting through all that. i'm going to try and remove the un needed smog stuff still left but it's going to be tricky telling what i need and what i don't.

[converted_to_datsun]

soooo i found a big part of the problem. my coil was bad... figured it out cause i broke the positive lead and brought it the the auto parts store. the guy behind the counter checked and said it was bad anyway. I put a super stock coil on and now I'm not going through as much as and i have more power and less misfires. still need to tune it but it's allot better. oh and i replaced allot of the vacume lines with new line. in a couple weeks my buddy is bringin a friend of his who is a huge datsun guy to help remove the rest of the smog and un needed vacume stuff. which means i get to start on the rust repair soon.

 

i've never seen any but one of my friends said when he drives behind my truck there's a bit of blue smoke. i hope he was just mistaken the excess gas but i think i might do my valve guides now and hope it's not the rings