Misfiring

[Vance]

i have an aus spec hachi that has just had a small port 4ag put into it, and now when i give it shit it misfires badly (sorta sounds like a limiter)

if does it at different RPM but it has done it a few times at about 80 in 2nd gear. i dont have a tach so speed is the only way to guage it. with the stocko S diff, i think 80 in 2nd is about 6000 (thats what it was when i had the 4AC) so it cant be the limiter because that is at 7700 isnt it??

it did it several times today once at about 70 it was doin it really bad and sounded like it had no petty or some thing (which it cant be coz i had just over half tank) and almost every time ive gone up to 80 in 2nd its done it.
all the electrics are standard (5mm leads, they look like little drinking straws so small!) and the battery isnt that good so could it just be weak spark????


has this happened to anyone?? should i just take it back to the workshop that did it and get them to fix it?

[sic86]

Take it back will be the best thing, they did it so they should know what would be wrong.

Cheers

[mumblezzz]

Could be weak spark at high RPM. I had that problem when the coil was fucking out.

[Monster]

Happened to me- check your ignition timing, make sure that the crank is at TDC, inlet cam is at TDC (open the oil filler and look for the groove on the top of the cam) when this is all lined up, take the cap off your dizzy and make sure the rotor is lined up with cylinder point 1. If not, take the dizzy out and make sure the teeth are lined up.
From there it could only be plugs/fuel pump/filter/airfilter
Goodluck

[DRFTAE86]

I had this problem wen i first put in my 4ag.
I later played with my dizzy, by sliding left or right to clam the idling down.
By doing this the car idled smoother and i never had the problem again.

[Black_Hachi]

i had kinda the same problem once, ensure all the wires are connected together. along the fuel rail, injectors, plugs, coils/dizzy etc.

My old car did what you are describing after the engine temperature wire running to the computer was not plugged in.

[DRFTAE86]

Oh yeh, my TPS was stuufed, so that could have added to the problem.

[screech]

a lack of spark at high RPM is usually cause by the coil not having enough time to "saturate" properly. saturation occurs when the magnetic field in the coil is at maximum when switched on, when the power is removed the field collapses causing a huge voltage spike which is directed to the plugs.

my guess from what youve written, is that

a- your coil or igniter could be faulty
b- the dizzy is not advancing the timing properly when you put your foot down
c- your alternator could be not charging at a high enough voltage, less voltage=less spark=less power