720 hesitates

Post by **hauntingurcoma** » Thu Jun 04, 2009 7:15 am

10 of 85 720 z24 carbed starts right up idles good when i let out clutch it stumbles wants to die put the clutch in and idles fine again.hesitates through out all gears but clears up at about 3500 rpm.Ran great until a week ago.changed plugs,fuel filter.any ideas??

Post by **seang** » Thu Jun 04, 2009 10:17 pm

It sounds like you might have a vacuum leak somewhere. Where that is I haven't a clue and you would have to go through all the hoses to find it. Something might be wrong with your carb, too. If there is, get a Weber. They are cheap used, and even new they are about the same as the stock s***-tachi. My old shop manual said that the carbed z24's had distributor problems, but I can't testify to that because I had a Fuel Injected z24.

Post by **hauntingurcoma** » Sat Jun 06, 2009 5:45 am

ok ill start with the hoses ty

Post by **Supererogator** » Sun Jun 07, 2009 8:34 am

I second the hoses. I had one come off before I replaced them all because it was ...well, olld. My truck did very similar stuff. Not a z motor, but....

Post by **breadbox** » Sun Jun 07, 2009 1:40 pm

I third the hoses. but if you have a slight leak its best to just replace it hose by hose. finding leaks itsn't as easy as they make it sound.

Post by **hauntingurcoma** » Mon Jun 08, 2009 6:55 am

i will do that. also does anyone know which coil is exhaust and intake? how do u tell?

Post by **hauntingurcoma** » Mon Jun 08, 2009 2:07 pm

i fixed some hoses and did cap and rotor.its better running just sounds like a miss at idle now

Post by **breadbox** » Mon Jun 08, 2009 3:51 pm

Have you looked at your valves yet?

Post by **jump** » Mon Jun 08, 2009 5:12 pm

do ya'll know if we can just eliiminate the whole vacuum get-up and plug a hole or six and have a better running vehicle...???

or not?

are the guys that race these things pulling the vacuum system out or what are they doing to hot rod the z24?

Post by **Supererogator** » Mon Jun 08, 2009 6:43 pm

It is my understanding that Japanese vehicles of this age, are very reliant on the vacuum system. Best to leave it in. I also know that many people have disconnected some of the emissions control stuff, and this has been done to mine, but I fixed some of it up when I replaced the hoses, and this has made it a bit more consistent.

You might also look into the timing, plugs, plug wires, and firing order. These can all be issues as well.

Post by **hauntingurcoma** » Tue Jun 09, 2009 3:52 am

plugs are new,ive double checked firing order according to the book,havent done wires yet but look in good condition.any certain brand of wires msd accel,i work at a toyota dealer in parts and our sister store is a nissan dealer should i get factory wires.they ordered the fuel filter in the pump for me still waiting for it.Can i just loosen and turn dist. to adjust timing like old chevys?

Post by **breadbox** » Tue Jun 09, 2009 4:00 am

I go with the rule of thumb that people use round me. Unless you are using and aftermarket ignition system.

Jap motors get NGK

Ger motors get bosch

US motors get whatever.

Post by **seang** » Tue Jun 09, 2009 6:11 am

Just for good measure, check that the coils are grounded out enough. My roomate had a z20 in a 200sx that ran like ish when the circuit failed.

Post by **Supererogator** » Tue Jun 09, 2009 1:27 pm

Being a Ford guy, I cannot confirm nor deny that your distributer timing adjustment is about the same, but, my mom's 46 Chevy and my 80 Datsun are not so different. My mustang is similar too, so I would say, yes, loosen screw, plug vacuum advance, and get out your timing light.

BTW-I like Autolite for old US cars....but whatever works...may just be the Ford in me.

Post by **hauntingurcoma** » Fri Jun 12, 2009 8:21 am

changed fuel pump filter,think i got all vac lines,noticed the butterfly on carb is always open hot,cold am,pm shouldnt that be closed at some point? tried turning dist but didnt help.

Post by **Supererogator** » Mon Jun 15, 2009 11:46 am

Mine seems to be open a lot more than my old Ford did, but it does close from time to time....I have not played with it because it seems happy. I would clean out the carb and make sure all the parts are moving and not damaged. My factory manual for my '80 has lots of notes about cleaning in this kind of situation. Again, not a z engine, but it might be the next step.

Post by **2kredz3** » Fri Jun 26, 2009 11:23 am

hauntingurcoma wrote:10 of 85 720 z24 carbed starts right up idles good when i let out clutch it stumbles wants to die put the clutch in and idles fine again.hesitates through out all gears but clears up at about 3500 rpm.Ran great until a week ago.changed plugs,fuel filter.any ideas??

ah yes, check the vacuum lines that go to the passenger side fender where you will find the vacuum switches for clutch release switch and trans in gear switch. what these do is cut fuel when activated under off throttle conditions to save gas and decrease emissions. if the hoeses look good buy a haynes manual and it will tell you how to test those to make sure they are working. if they are not working right then you will have this problem.

720 hesitates

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