DD76

Following up to thank everyone for their assistance. I was away from the garage for a month with a hip replacement. I did go ahead and replace both valve seals in cylinders 3 and 6 as they were the obvious places to start. It actually made no difference. A couple of things I learned in that process (1) filling the cylinder with rope and then turning the cam just a bit further to TDC was a great suggestion (2) whacking a spark plug socket set on top of the spring unit is a very effective way of releasing the keepers and (3) removing the rope after reassembling the spring makes it a lot easier to reinstall the rocker. After doing those with no benefit, I was pretty much resigned to getting professional help with the rings. I decided to try soaking the pistons for 36 hours with Berryman 12 and then, as they direct for an engine flush, I added about 10 ounces to the oil through the dipstick tube and then ran at idle for about 15 minutes. I then changed the oil and filter. I took it for a 100 mile ride. Checking the oil afterward, it had used a half quart, not great but an improvement. I then changed the oil and filter again to make sure all the Berryman was out but this time, used 10W-40 instead of 10W-30. I've now driven the car 200 miles since this last oil change and have used no more than a couple ounces of oil, if any, and no smoke. I have to assume I had one or more oil control rings stuck in the two years it was off the road for the fuel injection rebuild. I'm guessing, as it's been driven more this year than it has in the last 5 years combined and its been improving in oil usage over the summer, and maybe with the Berryman help, that the ring(s) broke loose and started to function correctly again. Anything I'm missing? Thanks again. New question...In the following photo of the plugs today. Plugs 3 and 6 are still dark compared to the others where the ceramic still is white. All the plugs were changed at the last oil change so I assume I have a second issue of imbalanced air/fuel mixture. There has always been carbon buildup on the back bumper. Is this an injector issue? They are Standard brand and all new. Would a temperature range change on those two spark plugs be a thought? All the usual culprits like AFM, Temp Sensor, etc. would seem to be across the board items not individual cylinders but what do I know.. Any thoughts would be great. Right now I'm just thrilled that the oil problem seems to be fixed. Thanks again to everyone.

That makes good sense. Thank you.

Thank you. That’s a great idea to just concentrate on those two cylinders. Definitely seals would be an happier fix than rings. Are you thinking that oil entering past the exhaust valve would more likely be going straight to the headers and not so much burning as the reason to center on the intakes? Thanks again.

Thank you guys. I replaced the PCV valve when I thought this was a fuel injection issue. After your post, I took the valve out to double check. It moves freely and looking in the motor end, it's nice and new looking. Something that did cross my mind is that my last oil change was with Lucas Hot Rod/Classic High Zinc 10W30 and the weather both times I took it the car out was in the 90 plus range and very humid. The dash temp gauge was a little high, picturing the pointer like a clock hand, it was at 5:30. Today it finally dropped to the low 70's so I got it out for a thirty mile ride. The temp gauge pointer "clock hand" was steady at 6 and, measuring tonight, it looks like I only used 3 or 4 ounces of oil. Not great but a big improvement. I'm thinking, as the car rarely is on the road when its under 60 degrees, that changing to heavier oil going forward after the valve seals replacement would be a good move. Would 10W40 make sense or something else? Thanks again for all the help.

Thank you for the thoughts Captain Obvious. I do think it's burning the oil. I did not check the reading on the dipstick before I did my first 25 mile ride but the last time I had checked, at most 10 or 15 miles earlier, it was about full. When I checked after that run it was noticeably down into the crosshatched area. The next morning before the 50 mile run, I added no oil and rechecked the dipstick. It was sitting about 65 per cent to the upper end of the crosshatch. I actually had a good reference point using the number stamped on the back of the dipstick. After I got done the 50 mile ride I checked the oil and it was below any of the crosshatching, checked it the next morning, and again just now, and it's a little below the crosshatching. Assuming the crosshatch area represents one quart, I've actually lost the better part of a quart. There's no oil on the engine or the floor. I'd think if it was leaking into the clutch, I'd have clutch issues and no smoke. Granted a rear view mirror is not the best measurement tool but I am surprised at the amount lost because I really only saw very visible smoke starting from stop lights and some of the times I tried heavy acceleration or deceleration. I did ride it pretty hard, shifting at higher RPMs, etc. As noted in an earlier post, the smoke does not seem to occur while the engine is warming. The two mechanics I showed the plugs to both used the term blow by and felt the valve area was the place to start. I figure, no matter what, oil has to be coming from around the piston or through the valves so $100 and my time to do the seals (maybe live to regret) is a good first step. If it doesn't solve the problem, time for plan B. Dealing with valve jobs or rings is likely out of my league. Thanks again for the help. Is there something I could be overlooking?

Thank you Dave WM. I was wondering if the compressed air or rope plan was best. The extra hand cam turn to compress the rope is a great tip. Thanks too for the reminder on rags. That seems to be at the top of everyone's list. I do appreciate the help.

Thank you all for your suggestions and advice. Though the job looks to be nerve wracking, until at least the first cylinder is done there are enough suggested write ups and videos to give good direction, particularly as it doesn't need to be on the road the next morning. The small investment in seals and a spring compressing tool looks to be a great way to either solve the problem or eliminate one of the two most likely sources. Thanks again for the help. Great site.

Thank you for the responses and imput. Finally, in the last two days, my smoke issue has been controlled enough that I could take the car for an actual drive. Went 25 miles yesterday and a good 50 miles today. I brilliantly deduced, as I lost half a quart of oil in today's 50 miles, that my smoke has nothing to do with the fuel injection. Attached is a photo of how the plugs looked at the end of today's run. They only have about 80 miles on them. Smoke was most evident starting from a stop but also some accelerating and decelerating. As an aside, the car ran extremely well. I also did a compression test this afternoon and had 145 pounds in #5 and 150 in the others. I took the plugs to my neighborhood general repair shop. I've clearly got oil problems in cylinders 3 and 6 and they suggested I should be looking at the valve area as the source because of the decent even compression. Noting Zed Head's comment above about valve seals and seeing those seals in a number of post, would that be a potential culprit in this scenario and is there a way to confirm that as the case. They also mentioned trying an oil additive designed for valve trains. Has anyone had luck wit something like that. Thanks again.

Sorry, pushed the submit button by accident. There's no smoke, or a negligible amount, until the engine temp gets to 100 or so, and then gets increasingly more pronounced at operating temp. Because of this, in the testing process I've spent a lot of time on the two temp related sensors, air temp and water temp. I've tested both on and off the car including putting the air temp sensor in a box and raising the heat from 20 to 110 and immersing the water temp in a jar of water going from 40 to 180. In both cases, measuring along the way, the results for both sensors aligned perfectly with a curve I found a while back on this site. Yesterday was the first time it struck me to test these two at the 35 pin right after shutting it down at full operating temp. I got 1300 ohms on the air temp with an outside air temp, measured at the AFM, of 98-100 and got 280 ohms on the water temp at about 175-180. Both look to be right on. The water temp sensor is new. It also has a new connector and a new pigtail back to the bullet connectors which were replaced. Generally, every 35 pin test in the bible has produced the results expected and every wire to the 35 pin has been checked for continuity as well as any leakage to ground. I suppose there could be some sort of abrasion inside the harness but I would think that would result in more inconsistent results. I've been through these tests 4 or 5 times and always get the same results. I've also been through the physical tests in the FSM with the exception of the relay and the dropping resistors. I couldn't imagine they were the problem and figured I'd only add to my problems in messing around with them. I did the noid tests on all injectors and and got brighter lights with the temp sensor disconnected. Fuel pressure at idle is about 31 psi and vacuum of 16 inches. The dropping and rising when increasing and releasing the throttle matches results documents that I found on this site told me to expect. I've forgotten what they actually were. If I pinch the return fuel line, the engine sputters. Fuel filter is new. All new injectors (Standard) as well as all new fuel hoses everywhere in the system from the steel lines near the alternator forward. I've tried a number of times to detect an issue with the FPR that might be leaking fuel into the manifold. Can't find a trace of it. I've also tested the cold start valve by plugging the fuel hose to it and finding that the smoke continues. I reconnected the hoses to the carbon canister, including a large hose running from the manifold to the canister, a smaller one that t's to the distributor and the throttle body, a third to the fuel tank and a fourth that is capped off. The thermotime switch is new, as is its connector and pigtail. All wire connectors, excluding AFM, are new. Other than originally cleaning it, I've done nothing with the throttle body. It gives the results expected in the idle switch, full throttle switch resistance tests. The AAR works as expected. The AFM gives all the correct resistance at the connector and at the 35 pin. When doing the test where you apply 12 volts to 2 pins while reading voltage on two other pins as the shutter is slowly opened, the voltage range is 7 (closed) to .2 (wide open) with voltage dropping quickly in the first 50% of the swing. It does have one issue where testing the voltage there is a moment, going below 6 volts at about 5.8, where it drops to 0.0 for just the tiniest amount of time then returns to 5.8 and continues on without a flaw. Someone adjusted this in the past. I tried the fingering adjustment Atlantic Z describes, couldn't see a difference so I put it back where it was. Outside of fuel injection, the engine has 150 compression in each cylinder. A leak down test showed 96 per cent retention in 2 cylinders, 93 in two and 90 in the other two. Any air loss seemed to be felt at the oil filler cap. Oil looks fine as does the coolant. No leaks anywhere. No overheating or oil pressure issues. I just removed BPR6ES plugs and replaced with BR6ES as suggested on the NGK site. The plugs I removed were all heavily coated in black soot. The car is a California 76 model. It is stock with a couple exceptions. It has a 75 intake manifold, which has everything the same without the extension for EGR. Obviously, all EGR stuff is removed. There is a blue wire that went to a fourth sensor on the thermostat housing which has broken off. I believe it's part of EGR so I've ignored it. The car has MSA headers and a custom stainless exhaust. Other than removing the non functioning air conditioning components is about all that's been changed. If I've missed something, please let me know. The car sounds great. Starts quickly, idles smooth and runs better than it has in years. It just blows an embarrassing amount of smoke. I apologize for the long post getting around to probably a stupid question. I assume, as there was such carbon buildup on the plugs, that there might be buildup inside the cylinders as well. Could it be that this stuff heats up and begins moving back through the system the warmer the engine gets? If this actually makes sense, does anyone have a thought on how best to check for, and remedy, that? Again, thank you very much, in advance, for your time.

Thank you for your responses. Just an update and more detail about my situation. I ran the FSM ECU test on the two new ECUs. I got a noid light response on the ECU I got from EBay, then used it to start the car and it ran fine. I let the car warm up to operating temp with no smoke and thought it had solved my issue. No luck, the smoke returned as I was taking it for a test drive. The smoking issue increases as the operating temp of the engine does. There's no smoke, or a negligible amount, until 1

Hello, Just joined. My first post. I have a 76 280Z with manual transmission and have owned it for about 24 years. a year ago I ran into a leaking injector hose (original) which has cascaded into a replacement intake manifold, new injectors, all new wire ends, a couple new sensors, etc.. When completed it sounded fine but smoked like a crop duster from the exhaust and there was a lot of carbon buildup. I've gone through every test for every component as shown in the bible and the FSM and now it sounds great and I'm getting a lot less smoke though it's still not right. At this point, as it's also clear it's been running somewhat rich for a long time, I figured it would be worth trying a different ECU to see if it would make a difference. I have the A11-600-000 with only pins at 26, 27 and 30-35 on the lower row. I got one on Ebay, pulled from a working car, with the same part number though it had all 35 pins. I installed it and the car would crank and crank and not start. I put the original back in and the car started right up. I then figured I'd have better odds to try one from a good parts company and got a remanufactured one, boxed as compatible with the same part number, same 35 pins, same car cranks and nothing. I put the original back in and it starts right up. I did take the case off the Ebay one and there's only solder connections on the same pins as my original. The others are all just dummies. Obviously, I don't want to mess with the other if I plan to return it. My hope for expert advice, as this is the best forum I've seen on FI, is am I overlooking something, are there some real year to year to year ECU issues, or did I just get a couple that aren't going to run in this car? If that's the case is running through a few to get a good one not uncommon? Thanks very much in advance. I appreciate it.