J Taylor Posted September 5, 2002 Share Posted September 5, 2002 5 months and counting trying to figure out this problem. I have checked or replaced EVERYTHING I know to, and then some. The car is a 77 280z with a zx turbo motor and wiring harness. The car runs like **** . It doesn't rev like it should and will only rev to 4500-5000 but really works hard to get that. Will make no boost. Compression is good, leakdown is good. There is a pop pop pop pop sound coming from the exhaust. Can also faintly hear it in the engine bay as well but can't pinpoint where it's coming from. Even though the motor checks good could there be anything internal causing this? ANy help would be great. About to have a nervous breakdown over this. JT Quote Link to comment Share on other sites More sharing options...
Grog Posted September 5, 2002 Share Posted September 5, 2002 JT, My initial assessment based on your inputs is that it is a timing problem (to start). Timing is crucial in any engine, but combine bad timing with an engine under boost -- you have problems. Is the popping sound noticable at any engine RPM, or at a certain point? Bad timing issues can present this type of problem and can be corrected. Also, if you are not seeing any boost, it could be a bad gauge or turbo. If the engine ran fine beforhand, but suddenly took a nosedive, timing and turbo problems can quickly manifest and creat a plethora of headaches. I am not a turbo guru, but in my experience there is a simple yet effective fix that is typically the solution to common problems. I would bounce this question onto the Turbocharged post. I am certain someone has experienced this problem before and can help you out of this bind. Grog Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted September 5, 2002 Share Posted September 5, 2002 Hmm...have you checked for any split I/C boots? It doesn't sound like an internal engine problem. Usually, even if you have hardly any compression, you will still be able to rev. It almost sounds like you're running extremely lean...does it have the same problem if you're just sitting there idling and then goose it to rev it up? If so, try mixing in a small amount of propane via a vacuum line (do this with care, please) to richen the mixture some...if it runs better with the propane mixture, then you're definitely running way too lean...which, could indicate a torn boot, bad AFM, or other problem... I posted a link to build your own intake leak tester (not to be confused with a leak down tester or compression tester) that you can use to pressurize your intake system to check for torn boots, cracked pipes (not crack pipes), or any other boost leak source... Quote Link to comment Share on other sites More sharing options...
J Taylor Posted September 5, 2002 Author Share Posted September 5, 2002 AWD92GSX: That link would be great. I have thought about an intake leak but havent't been able to find one despite spraying several cans of starting fluid all over the place. Other than that, the AFM bench tested fine. The turbo spins freely and has no play. Cam timing is good, timing is set at 20, new cap, rotor, plug wires. Replaced distributor, coil, MSD box, igniter, ECU, bench tested wiring harness and it and all sensors showed good. Good fuel pressure. Injectors are all firing and all have an ok spray pattern. I'm sure there is more I have checked that I can't think of at the moment. When running, it FEELS like cam timing is off. After a timing belt job on my 84 300zx turbo the cam timing was off and would run very similar. Would idle less than perfect, make a small amount of boost until about 4k then bust up bad. Like I said, everything internally checks out fine but Im about to the poing I want to pull the motor back out and apart and just look at everything and reassemble. JT Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted September 5, 2002 Share Posted September 5, 2002 If the suspicion is that it is lean, disconnect the head temp sensor and see if it runs better. My turbo 240 had issue's with the first harness I used, and I never could get it right so I ended up replacing the harness. It would not run right, and I had to disconnect the head temp sender to make it run, but it was to rich. I used resistors, but that was a pain and they always ended up breaking or something. I went thru all sorts of stuff trying to make it work. Have you checked fuel pressure and flow? That could be another area. Of course with a presssure gauge and a test drive, pressure will drop if flow is not there. If you have a leak in the hoses after the turbo, the car will be rich once boost hits, not lean. I had a turbo that leaked around the compressor housing, and it was the most frustrating thing to track down. When I hit 0 psi, the got black smoke and stumbling, and eventually it would clear up and run right if you stayed in it. When I fixed the leak and drove it, it boosted instantly to well over 20 psi and popped one of my intercooler connector hoses that was rubber, and I had to use some duct tape just to get it back to the shop to replace the hose. Quote Link to comment Share on other sites More sharing options...
J Taylor Posted September 5, 2002 Author Share Posted September 5, 2002 If you disconnect the temp sensor it will die after about 5 seconds. How did you figure out the leak on the compressor housing? Like I said, I have sprayed several cans of starting fluid over everything and can't find any leaks. JT Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted September 5, 2002 Share Posted September 5, 2002 I did not have a stock turbo, but a Rayjay, and although hard to explain, the compressor housing physically bolted to the backing plate. It was a really sweet turbo as far as taking it off the car and dissasembly. To bad it broke. What are the plugs gapped at? If they are much over 40 thou, that is to much. This is a real long shot, but is the harmonic dampner loose? Seems like I had misfiring issue's on an NA engine with a loose dampner. I still would like to see what the fuel pressure and flow is like. I would suspect you should be able to get somewhere between a half to a full gallon in one minute. I really don't think you are to rich, I am leaning towards lean, or some sort of bad connection or faulty part. Also, this is a real stretch, make sure you don't have a shop rag stuffed into something in the intake plumbing. Maybe even go so far as to spray out the AFM with some brake clean. Is the coil weak? I can't think of anything else besides the harness itself. Quote Link to comment Share on other sites More sharing options...
J Taylor Posted September 5, 2002 Author Share Posted September 5, 2002 PLugs are gapped at .035. Not sure about how much the pump flows in a min but it sounds normal (loud T-rex pump). We pulled the fuel rail off and fired each injector seperately into a bucket and each looked good and had a decent pattern. Swapped coils with a friend and it didn't help. CHecked the harness by the factory manual to each sensor and it all checked out good. Any more ideas? JT Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted September 6, 2002 Share Posted September 6, 2002 http://www.vfaq.com/mods/ICtester.html I hope this helps... Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted September 6, 2002 Share Posted September 6, 2002 I agree w. LJ, check that Crankshaft pulley (harmonic balancer) bolt and make sure it is tight. I had the same problem on my 73... Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted September 6, 2002 Share Posted September 6, 2002 The only thing that makes me wonder if it could be anything to do with timing is that it is not making any boost... Now, usually, even if cam/crank/ignition timing is off, an engine will still be able to make boost, it just may be a little slow about doing so... Quote Link to comment Share on other sites More sharing options...
R0N Posted September 6, 2002 Share Posted September 6, 2002 I was having similar problems when my wastegate was stuck open. Ron Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted September 6, 2002 Share Posted September 6, 2002 Is the engine grounded properly? I would also double check that the harmonic balancer hasn't slipped. I had that problem on the engine in my 260. I would bring the number one cylinder up to TDC, verify the cam notch lines up with the gear, check the position of the distributor drive spindal, and look and see where the notch is in the dampner. It should line up with the 0. If any one of these is off, that is likely your problem. I can't think of anything else. You could be off just a tooth on cam timing, or on the distributor position. I have lined up my cam timing right before, only to have it off, so alot of the time, I will turn the engine over a couple of times and recheck it. Don't know why that happens. Quote Link to comment Share on other sites More sharing options...
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