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Good evening guys, So I'm back for more help. It's almost time to drive my 240z for the first time, but the clutch is stuck to the flywheel. You might remember me. I'm the guy who bought the 72 with a seized engine(that I got unstuck). I'm here because the engine has a really hard time running when engine cold. It's about 60 degrees in Chicago now . So it will start and revs to about 2500 for 2 seconds and shut off, try again and again the same thing. Over and over and over again for about 5 minutes. I'm messing with the throttle the whole time. After a few minutes of that , it runs and idle great! Other that a slight bog when I blip off idle. Sorry for the long story, just want to give some background. Thanks in advance guys

I have a question about performance and idle speed. I have a 78 280z, runs great, just replaced the one part it seemed to need to enhance its performance which was the lower pcv hose, the old one was crap. Boy what a difference the new one made... However, once I replaced it the idle went up from 800 to about 1000rpm. And I noticed the car's throttle switch didn't kick in to send it to full enrichment for full throttle application. So I lowered the idle to about 750 or 800rpm with the engine up to temperature of course.. Then I took it for a spin and it blew me away, I mean it threw me back in my seat, the performance was 1000 times what it was at the previous idle setting. My question is, how does the idle screw adjustment effect the idle? Is it adjusting airflow or does it control fuel flow somehow. I assume it's air... Any input from you guys would be great. Would love to know more about what's happening here.... -- Jeff..

Hello, kind folks of CZC, long time lurker here! Normally I can figure out my issues through the vast information already here but this is the first problem I came across that I feel the need to post and get some more direct answers. The car cold starts every single time and runs from anywhere to 30 seconds to 2 minutes. The RPMs bounce from around 750 to 1,000 until it puts up a fight to stay alive and then stalls out. Very occasionally white vapors will pour out the carbs trying to crank her right back up. After that I will have to wait about 5 minutes for it to crank back up. Now the problem first arose with some bucking on the highway, normally around in the 2,000 to 3,000 RPM range. Then it slowly came to the state that it is in now. Little bit about the car. 1974 260z. Stock 2.6L with Ztherapy carbs. Electric fuel pump. 77,xxx miles. Daily Driver. Owned about a year. I started the search for engine harmony in the ignition. Pulled plug wires until I came across #1 to see the tip of the plug and plug wire was rusted completely. I then replaced with NGK plugs and wires along with cap and rotor thinking that had to be the problem. Same symptoms afterwards. I then started to believe I became victim of the timing chain jump myth but after checking TDC with marks on the rotor, cam, and piston everything seemed to be in line. Timing set to 8 degrees at 750 RPM's the few times I had it running well enough to do so. Valves were adjusted tight a couple months ago. Moved on to a dry compression test and the results seemed consistent enough to rule out any issues there. 1. 160 2. 160 3. 165 4. 175 5. 170 6. 170 I then moved over to carbs and disassembled the majority of the body and cleaned out what I could do the best of my ability. I came across a crack in the top portion of one of the floats. Would that possibly cause flooding issues after a certain period of time of running and cause the white vapors from the carbs? I redone the fuel tank and cleaned out the lines when I first bought the car so I believe all is good there. Clear fuel filter installed so I do see clean amounts of fuel flow going through it. Been running the same fuel delivery setup for months. Brake master vac always had a leak in it but spraying carb cleaner around other lines had no effect on RPMs. I grew a terrible stubble of facial hair to profusely scratch while trying to think of a solution to no avail. I feel like the problem is so minuscule and I may feel like a dummy afterwards but better a dummy that has a running car than none. I'm losing days at work, patience, and money at parts to trying to get it going again. Sorry for all the reading material. Any input appreciated guys!

I am starting to look deeper into the claim that later DCOE's Idle Enrichment Screws are typically turned-out further. The details in the screw interface to the carb body distill to: 1. For the same flow: A narrow tapered needle needs to be tuned out further than a wider tapered needle if the orifice size is the same. It is proportionate to 1/tan 2. For the same fuel flow, a needle with the same taper needs to be turned out more from a smaller orifice than for a larger orifice. So to compare an early carb's Idle Enrichment Screw turn-out to a later, one must know the taper of the needle and the orifice size. In another post I measured the threads on early and later DCOE Enrichment screws and it was 0.8 for both. The part number for 40DCOE151 Enrichment screws is 64750.003 The DCOE151's I am tuning have this needle: 64750.004 64750.001 is stated to be "38 degrees" and for "early DCOE carbs" 64750.002 is the air bypass screw From the above, the 003 and 004 do seem narrower than the early 001.

Hey so ive got a 73 240 with the 72 SU's with the emissions removed vac lines on carbs capped. only engine mods besides carbs is 79 electronic distributor, and electronic fuel pump. Well when I start the car it idles around 800 but after about ten minutes of driving the idle works itself to 1500 and doesn't come down from that. A friend told me it was was probably a vacuum leak because sometimes wen i turn the car off the engine runs for a second, and my heater vents blow cold air and defrost blows warm, and you can kinda hear a hiss from the engine when i turn it off that i cant find anywhere.... so I unplugged and capped the distributor advance and the brake booster but neither helps. I also sprayed starting fluid all over suspicious spots like intake and hoses. and only around the the throttle shaft where it meets between the two carbs did it seem to make any idle fluctuation. maybe this could be the problem? warn out? any help would be greatly appreciated:)

When the heater blower motor is not running the idle is a little rough......you turn the fan switch on high the idle smooths out. I suspect this is a grounding issue, power draw, or relay issue. I wanted to see if this is a known issue, before I begin troubleshooting. It's comically repeatable, and I would normally expect the opposite behavior. I have good charging regardless if the blower is running or not.

My duel SU round top 3 screw runs crappy and is backfiring through the exhaust when you pull your foot off the pedal(deceleration) what does this mean, does it mean it is running rich? Any help would be appreciated. It is also running rough and seems to want to stall. I just adjusted the carbs and float.I set the floats at 9/16 they do not suck full at that point but begin when the float starts to drop, I used the FSM for the carb sync. any ideas ZDUDE1967

MY 72 Stocker has a bug.....when i warm it up i have notice the idle goes up 200-300 rpms when clutch is depressed? When i let it out in goes back down 200-300. What is going on? how do i fix this? thx

Well, earlier i had posted a picture of my engine all torn apart so i could clean it up a bit. Everything from the air cleaners to the Intake Manifold came off. It was running great before hand, but now that ive put it all back on its running really really fast. First time starting it up, once it had a sip of gas it went right up to 5k before i shut her off. I pulled the fast idle scew down as far as it could go and im still idleing between 3-4k rpm with the choke out in the fully forward position. I havent moved any screws on the carbs while they were out and i put the choke lines back where there were in the first place. So which scews do i use and which way do i turn them to get the revs lower? HELP! :-P Heres what we have

The car starts up pretty well, though every once in a while it'll immediately die, and takes some coaxing with the accelerator to get it to stay running. When idling, at first rpms will hover around 800-850, then slowly drift down. The car starts running rough, rumbling, until it gets down below 700 rpms and dies. Also, when coming to a stop and idle after swift acceleration, the car stinks of exhaust fumes and gasoline. Is this a fuel injector problem? I was going to replace my fuel filter; would that be a waste before i know what's causing the problem? --------------------- 1976 280z Automatic