WRC17 Posted April 6, 2014 Share Posted April 6, 2014 Ok, I've been having this issue for a while now and have been searching but I can't find anybody with a similar problem, so here we go. I have a stock 77 280Z L28. Sometimes when I start the car up when the engine is warm, I get really low il pressure and the engine seems to stumble a lot and has low power. If I start driving the stumbling slowly dies, the oil pressure rises, and I have full power. Is this an oil pump issue? Fuel? I'm really stumped. Thanks for helping! Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 6, 2014 Share Posted April 6, 2014 Sounds like the hot start / heat soak problem. The injectors and/or fuel rail get hot and fuel metering gets screwed up. It's a fairly common problem. The low oil pressure is probably from the low RPM idle. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 6, 2014 Share Posted April 6, 2014 Or, your "low oil pressure" is like everyone elses' prior posts and it's a defective sensor. If it's bad on one side, it may be bad on both...so the 'low' oil pressure is causing the fuel pump to shut off intermittently and cause the rough running... Determine what oil pressure you ACTUALLY have with a mechanical gauge. Second, make sure the fuel pump cut off portion of the switch is closed when the engine is running. Mileage can make low pressure, and in many cases putting a turbo pump will restore flow to mask the wide clearances causing the throwoff.... but you're a LONG way for that band-aid at this point. Likely, the most you need is a new oil pressure sensor! (Or proper weight oil, or proper idle speed adjustment, or...) Quote Link to comment Share on other sites More sharing options...
Phantom Posted April 8, 2014 Share Posted April 8, 2014 Reading what you said in your post it really sounds like a vapor lock situation which the earlier FI Z's had issues with. Does your engine still have the metal heat shield between the exhaust manifold and the fuel injection rail? Sometimes folks remove those to "clean up" their engine or just don't put it back on when doing some work on the engine. It is very important that it be there. It probably occurs after the car has been sitting about 20 minutes, correct? If it sits for about an hour you shouldn't be seeing the issue. The 280ZX addressed the issue with a cooling fan that blows air on the injector rail after the engine is shut down. I drove my 1977 in Texas for 14 years and only had that happen once or twice because all my shields were in place. Quote Link to comment Share on other sites More sharing options...
WRC17 Posted April 14, 2014 Author Share Posted April 14, 2014 Yes this is exactly the problem. If it sits for 10 or 15 minutes it doesn't run well. If I let it sit for an hour or so, it's completely fine. There is a shield in between the exhaust and intake. I plan on installing an electric fan soon, so hopefully that could solve this issue. Are there any other things I might be able to do? Quote Link to comment Share on other sites More sharing options...
Phantom Posted April 17, 2014 Share Posted April 17, 2014 If you don't have the 77/78 vented hood you might get one of those. It will let the heat out of the engine bay better. My car is a 77 with the vented hood and I had very few occurrences of what you've been experiencing. My total fix, however, was when I pulled the L28 and installed an LS1. Quote Link to comment Share on other sites More sharing options...
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