Missing down low

[oldmates260z]

I have a set of 240Z SU?s on a 260Z and from a standing start is often misses or hesitates to get of the mark, which can be a bit of a worry crossing a 4 lane highway. :shock:

It is better once it has warmed up plus if the choke is out. Also it will take a big miss and backfire on hard acceleration at about 1500rpm when it?s cold.

 

I am guessing that it is mixture, but how do you best set that? Any other hints?

[JP240z]

there are mixture screws underneath the carbs from memory.

if its doing it when its cold, its probly lean?

[tattoo_ink]

yep i agree with jp.......have you checked for air leaks or cracked hoses maybe ? chris.

[zedrally]

Don't discount an electrical problem, I had put up with erratic running for 14 years always blaming mixture and air leaks.

 

Last week I had the ignition system looked at after cracking it.

 

Result, ignition componants where basicly stuffed after 30 years, new coil, ballast resistor, new crimped and cleaned contections have resulted in an unbeleavable increase in performance, even the tacho works now!

[nat0_240_chevZ]

missing on a single cylinder would indicate an ignition problem or a compression problem but not to the extent that ign would cause.

 

disregard the leaks and inlet trouble listed above, try new plugs, leads pionts, condensor (if running points dizzy still), ballast resistor, tacho lead in 240z layout. As the tacho is looped through on its way to the coil.

 

Also a compression test is easy enough to confirm head integrity along with gasket, but ignition is my #1 bet.

 

nato

[oldmates260z]

Thanks guys. I have bought a while ago points, coil, dist cap, rotor button to get everything new again. But have yet to put them in.

When we bought my sons 260 we can down Mt Tamborine in mine, trailing throttle all the way I fouled No 6 plug and put in a new set then. Also she uses a bit of oil.

I was hoping it was one bad plug as it has not fouled again. I think a new set of leads are in order as well.

What is your experience with burning oil when trailing off then accelerating. I thought that used to be valve guides, but seems to me to be more like rings.

Thanks again guys, input is great