Rill Cosby

That's what I like to hear! No offense to the guys above that responded first and second but that's kind of the reason I am reluctant to post. In there defense, you can find a discussion about almost every problem that has ever been had with these Z cars with some sort of input or solution. Hell, I've been a member since 2012 and lurking since 2011. I rarely have to post or contribute because of the insane knowledge you and other users already have here. The database is huge and the community is overall one of the nicest and most helpful I have seen. That being said, I sometimes find it counter-intuitive when told to use the search forum, especially when stated that I have exerted all my searching options. But I do get it, really. I think my 260z before the engine rebuild may have spoiled me. It also surprised others how well it ran or more specifically idled. I know it's not advised to do so but I could barely touch the key and it would crank without the choke with no hesitation in even cold weather. Of course, it would run a lot better when it warmed up but rpms were never an issue. In the warmer weather, it would crank right up to roughly 750 rpms and hold it no matter the temperature of the engine. I know the above sounds kind of whiny but the 400 - 500 rpms that increase is way too much. Something changed somewhere whenever putting in the rebuilt engine. That doesn't narrow down much haha. But everything outside the internals of the engine have remained the same. No issues with first hitting the throttle, no stumbling at all, on cold starts. The hesitation and then stumble does occur during startup after I restart the car once it's warmed up. Usually after some throttle it goes away but at this point RPMs are back up to around the 1200 area. Side note, I've read hundreds of your posts at this point. Were you one of the users who got there hands on a 123ignition distributor? I guess I should use the search function.

All my searches begin with or include classiczcar. Then the google correction of "did you mean: classic car". Then clicking the search instead "classiczcar." My favorite is when it doesn't offer that option. I then go to other forums. I've had this problem for months and have periodically searched this topic on this site and I'm sure there probably is a similar situation on this site somewhere but it has eluded me so far. I've only found one that was kind of close and it just ends abruptly. Everything else I find is "hesitation, rough idle, rpm drop, fluctuations" and are usually combined with an action to cause those things as braking, clutch pressing, etc. I know every forum frowns on not using the search function so I try my best to find it first. Thank you, I need more than luck!

I wasn't sure where to post this and this is my second post in two days but this should be the "last" real big problem I'm dealing with after the rebuild of my engine. I honestly thought when this issue appeared that Google would have tons of information on this issue. Maybe my google-fu is getting worse but I can only find topics along the lines "hesitation after warm up, rough idle after warm up, etc." It seems like the only thing I could find similar was a guy having the same issue, but with his boat. Still gave it a read. The issue I'm having is that no matter where I set my RPMs it will always increase about 400-500 RPMs after warming up making it difficult to have it tuned well. I'd assume that it is vacuum or carb related but I am wrong a lot when it comes to these things, as my post also proved yesterday. It also fires up right away on cold start. After the warming up and the RPMs have raised coming back to start a warm engine sometimes then it is hesitant. I'm running the Ztherapy carburetors, before the rebuild they sat covered indoors for about 2 years. They were cleaned before they were taken off and once put back on I had fuel issues that ended up being pump related. I still dissembled the carbs and cleaned them. I didn't see anything that looked like a problem but again, I'm no expert. Choke is also moving freely. I've contemplated the thought of a tune up kit for the carbs but I don't know if needed. On to vacuum, I've checked all the lines I can think of. I DO have a leaky brake booster that will hopefully be replaced this weekend but I've had a leaking brake booster way before the engine was rebuilt. The RPMs, back then, only fluctuated when braking, as it should. Before this rebuild the car ran like a top before it's catastrophic failure. Actually, it ran better than it does now which is a bit disheartening. Especially on idle and when given gas. Checked and torqued all manifold bolts. With the rebuild came all new plugs, wires, cap and rotor. Also not sure if related but distributor holds a vacuum. Timing has been checked multiple times and seems correct. Valve lash also checked multiple times. Compression is 165-180 through all pistons. I'm unaware of the fuel pressure but it's all the same setup as I had for years. Car runs through the RPM range just fine. It's just that RPM rise when warmed up. I guess this post is more about bouncing ideas around. You guys have a lot more experience than I do and always have a better idea of what to look for or where to start. I do all that I can before coming to post on the forum. Sometimes it's just something easy I've overlooked and I feel dumb (which I definitely prefer) or it's a PITA or head scratcher like when my transistor ignition module was going out years ago. Maybe the two things I assume that could be the culprit actually have nothing to do with the problem. Thanks for the read!

I think you may have hit the nail on the head with the water pump! One, it was such a deep sound I would have never expected it. Two, I'm not so confident with engine rebuilding I was quick to assume that something had gone wrong internally. I filmed the video panning across front to back for that very reason. I definitely heard more from the front and I'm glad it came across in the video. I really had a feeling it was piston #1. Something simple, I never would have thought of the water pump sadly. I pulled it off, ran it for a quick second and the sound seemed to have disappeared. Thank you for the help, bud. I've read so much of your information on this site. If I remember correctly you went under a different alias in the past. I think it may have been solved already. The exhaust manifold was one of the first things I looked at, I should have mentioned in my original post. I know when that leaks some wonky sounds can occur. Thanks for chiming in!

I'll give it another go later tonight. I mentioned in my post that I have tried that. I read somewhere that even pulling two side by side might narrow down something (bearingwise?) but I don't recall off the top of my head but I've tried that too. I've tried the flathead screwdriver to the ear method but like I said I'll give it another go tonight and report back with something more accurate.

Where to start? First off, my username didn't age well. Secondly, it's been years since I've bothered you guys but I need the help this time. I usually try to do as much as I can on my own before I bother you nice people and usually there is enough here already to fix most problems. I have read a lot on engine noise but I cannot pinpoint this one. A couple of years back my 1974 260z went through a rod bearing. The actual nut on the rod cap backed out while driving and you can guess what happened next. The motor then went through a rebuild about 7 months ago containing a new crankshaft, some new rods and pistons. Everything went pretty smoothly. Roughly about 6,000 miles on the rebuild now. Then problems started to happen. First, valve train noise to which I found to be rocker arm jumped off a lash pad. After that was fixed there has been a little noise there since. I know these heads can be noisy but it sounded different. I've checked valve clearance 3 times since and all lash pads seem to be intact, also the springs. I checked and cleaned the oil bar as well. Where my stupidity comes in, I went with a 20 weight oil (my defense, it's also very hot here) and only after about 2 short distance drives I realized that was a mistake and I switched back to 10w-30. I only mention this because this is when that sound seemed to get worse and started to sound not so much from the head. I thought the thicker oil may have had trouble getting into rod bearings so last night I had a look at those. I'm not an expert in this at all but from what I could tell all bearings looked perfectly fine. Everything was properly torqued before and after. Compression is about 170 through all pistons. Plugs seem fine, maybe a little rich. Checked timing multiple times. The car still runs strong, maybe not as strong as before the rebuild which bothers me a bit, but she cranks up and runs fairly smoothly every time. The knocking sound only occurs around 600-800 RPMs. Seems like it's coming from more from the front of the engine. Pulling plug wires while running doesn't seem to change much. At this point I'm not thinking logically anymore and about to start throwing money. Possibly going through all new ignition parts again. There seems to be some fresh black carbon buildup on piston #1 which maybe isn't getting a good spark for some reason? I don't know. Sorry for the long post and I'm sure there are things that are missed. Hopefully the video will do a better job of describing what words can't. Thank you! 20190510_162316.mp4

Sorry for getting back so late to this topic, I've been so busy lately since the car has been running and haven't really had access to another computer. I just want to clarify some things, just for future reference, if someone stumbles upon this thread. The problem did seem to be the ignition module. The car has been running fine since the new one was installed. I wanted to post some picture of the old, stock ignition module and the new one that I picked up. This is a picture of the old, stock ignition module. Almost like a soft aluminum casing that has a heat sink style to it. The number on it reading E12-05. Then a picture of the new one. I was aware the numbers didn't match up exactly, or I should say the extra letter didn't, on this one but the plug matched up and I was that desperate. Crossed my fingers and hoped for the best. The new one reading E12-05K. It's been installed and running fine since. The outer casing is completely different and so are the internals but I just figured they might all do the same job in the end. Hopefully it performs well in the long term. Sorry for the blurry picture. All in all, thanks for all the help guys. It would have been a long road trying to figure it out without you guys. I'll definitely be back again haha.

It has clearly became a overheating issue in the ignition module. Now the only problem I have is identifying is if the ignition module itself is bad or something external is causing it to overheat. I found a "never been used" ignition module with the same serial number and plug so I decided to go that route first. The cost was about double the HEI replacement but I would don't mind paying a little extra for a direct plug in and ease of mind of proper installation. That way if I experience any overheating afterwards I can narrow it down to the problem hopefully being something external. I'll definitely report back once the part comes in after a couple of days.

I plan on going through new hoses and clamps, hopefully sooner rather than later. The hole in the middle of the EGR mounting casting isn't pulling in any air.

I hate to have everything spelled out for me but I'm going to need it. So what you are saying is the quickest and cheapest method would be the HEI 4-pin module way? I should be able to go to the local auto parts store and pick up a HEI 4-pin ignition module, like the one in the Chevy HEI link you posted, pull out the old transistor module and wire in the new ignition module? What I'm gathering from the other links is that I would also need a different type of distributor than what I have now to run the new module. By the way, thanks for the patience and all of your help, and everyone else's input. I definitely owe you a beer or two!

Pardon my ignorance on this. I did some research and I'm still at a loss on what I exactly need or could use in a replacement for that part. The unit number on the transistor box is E12-05. I've only found one site that may have that part.

I believe so. The previous owner switched to the Ztherapy round tops. Everything else seems to be original. N36 intake manifold and balance tubes. Some emission deletes. The previous owner was amazing with including just about every single part he did remove and include it with the vehicle along with some spare parts.

You may have been right on the money after all. I decided not to give up on the electrical side of it just yet. I pulled out the transistor box completely, removed the back side this time and started running the vehicle. It stalled out as normal but when I would try to crank it over, it would actually start and die right back down. It did that every time now. So I repeated the process but this time blew air on it after it wouldn't start. Started right up. So I put a blower on the box and it idled for over ten minutes until it stalled out but it started right back up at the turn of a key. I even took a video of the process because I couldn't believe it haha. Of course, the idle is still a little jumpy but it runs, still running as I type this. I just have no idea how this transistor box is supposed to function. I'll definitely dig into some research tonight. This is where I have no idea what I'm doing. Could that mean the box's internals may be bad or something external causing the overheating? I really have no idea what I'm talking about. I need to get my hands on a multimeter.

As I was running the car I started checking electrical wires until I ran into a loose connection on the ballast resistor. As I shook the wire the car died out and I got excited thinking this could definitely be an issue. I flipped the resistor over to tighten the connection and with the slightest turn this happened. So all connections cleaned and tightened on the resistor and still having the same issues. I'm not sure how hot the resistor is supposed to get but I didn't think it would get THAT hot, to the point of burning my finger. Anyways, at least it's nice to fix these little things that can arise in the future. I did what I could with the transistor ignition box. I took the cap off of the box and after she stalled out again I took air from an air compressor and blew air all over it. I'm sure it wouldn't cool it off as much as using the upside aerosol can so it didn't help with any quicker of a start up. I even tried putting a blower on the box while it was running to see if it would prolong the idle time, which it didn't.

Steve, those sound like some very interesting things to check out later on today. I go out there everyday to work on it and find myself pretty much fiddling with the same thing expecting something to change. So anything new is appreciated. That link you posted also lead me to some other information that I could try to narrow out some issues. I seem to be getting good sparks from the spark plug wires and no erratic light flashes with the timing light, but I only checked #1 spark plug wire with the light for timing issues. I'll check through all of them today. The car was born and raised a manual. I've read a lot about people changing the ignition system in their Z's and the benefits but I always believed "Don't fix what isn't broke." Except, you know, it might be broke.

Air and fuel has been balanced at 2,000 RPMs whenever I did it last. After I bring it down to idle speed I never get a consistent idle. Sometimes I get an idle of 900, sometimes it'll find itself around 750. Seems to depends on how close to death she is. I've been checking timing with a light every day for the course of this week. Only time the timing changes is whenever I do so.

Rob, chokes open and close fine and do not stick. Steve, I'm using the stock ignition points system that came with the vehicle.

No smells of gas in oil. I couldn't locate anything in the FSM about symptoms of a plugged PCV valve, just some information on how to diagnose if it is working properly. Which does seem like it is working fine. Tonight I blocked off the fuel line, popped open the float bowl lids and just spoon fed the bowls with fuel just to see what it would do. Same symptoms, runs fine until it warms up. Steady 17 in Hg through the intake manifold where it would normally connect to the brake booster line. About 12-13 in Hg through the PCV valve.

You're absolutely right. I should have stated before that it's hard for be to believe that fuel pressure could be AN issue, instead of THE issue. I wasn't able to get my hands on a regulator today but I will try for tomorrow. I've seen the FSM on XenonS30 before and this is the first time it actually opened in WinRar for me so thank you for that. Any other variables to maybe look into while I'm out wrenching on it tonight?

Man, forgetting my FSM has been the biggest mistake of this whole entire situation. Don't rub it in haha. It's worth a shot. I might not be able to get my hands on a regulator today but I'll dig around for the stock pumps and try that. It's tough to think that too much fuel pressure could be the issue.

I never had to use the choke since she starts up right away when left alone for a bit. The choke doesn't seem to help at all when trying to start her back up after she stalls out.

Things I forgot to mention before and a little more information. The engine does experience dieseling after cutting off the ignition with the key every now and then. The fan spins in a counterclockwise direction and white smoke emits from the carbs. In my first post I was worried about the carbs maybe overflowing due to a crack in the float but forgot to mention that no fuel is coming out the carbs mouth. A friend mentioned the idea of one of the needle and seats maybe not sealing and fuel being let into the intake manifold. I checked for fouled plugs and smelled for any fuel on them without finding any problem there. It's being ran and has been ran on 89 octane since I've had it. After some stalling I checked the fuel bowl levels on each, both even, but they seem to only fill about a 1/4 of the bowl up no matter how I adjust the float levels. Levels are same after ran and after stalling. I measured a consistent 5 p.s.i right before the fuel rail with a fuel pressure gauge. I will do a better measurement of vacuum readings tomorrow. Still can't find any hints of leaks with starter fluid. A picture of the distributor rotor, of what I assume is right for TDC, for ghits and siggles. Ignition coil was replaced with no change in performance because I like wasting money.

Probably could have been put in a more appropriate thread category..

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!