ballizticbucket Posted May 29, 2009 Share Posted May 29, 2009 my 1978 280Z 5spd shudders and shakes between 1300 and 1800 rpms wether revving up or down. it also uses a half tank of fuel in less than 50 miles. the plugs are wet and black. theres no fuel canister, the egr is unhooked, the dashpot has no vacc. line attached, and when ever I pump the brakes the car revs up is that normal? the afm serial is a-31 618 420 is this the right one? newer plugs wires and I cleaned alot of connections but to no avail. it also revs up and down at idle and when I press the brakes it almost dies heres some pics of my engine, what would cause the shudder and other problems? im heading to parts store now to get a fuel pressure tester and more contact cleaner. other than the gas gulping and shuddering this thing idles high but it goes fast. thanx oh, 1978 280Z non turbo efi 5spd Quote Link to comment Share on other sites More sharing options...
sweetleaf Posted May 30, 2009 Share Posted May 30, 2009 Sounds like your brake booster is shot. I would fix that first, but you probably have some other problems too. Quote Link to comment Share on other sites More sharing options...
m4xwellmurd3r Posted May 30, 2009 Share Posted May 30, 2009 sounds like a bad brake booster and a seized fuel pressure regulator. Quote Link to comment Share on other sites More sharing options...
ballizticbucket Posted May 30, 2009 Author Share Posted May 30, 2009 ok, you said it could be a bad brake booster but my brake pedal is not hard to push, isnt that the main symptom of a bad booster? when I bought the car the PO said the front brakes are very worn and so was the rotors so he bought new calipers and rotors and pads but he didnt get them on yet so he gave me the new parts so I guess I have to put them on. could the bad front brakes make it seem like theres a booster problem or should I replace the booster when I replace the front brakes? Could that little valve between the booster and the manifold be bad and should I replace that first or just replace the booster? I hooked up a vaccuum line "T" and connected the dashpot along with a line that goes from the thing on the pass. fender that looks like an old plastic type septic tank. I dont know what it is but alot of vacc. line go to it and the round thing above it. my car runs hotter and now my oil gauge barely moves. The line that came from the tank thing had suction so should it be hooked up to the manifold if it already has vacc? or will its suction counter act that from the manifold? I'll post pics as soon as the batteries for my cam finish charging. also how many full turns (from fully closed) should my afm adjust screw, the idle adjust screw and the dashpot be when set to factory specs? All have been messed with so I dont know how to adjust without starting at fully closed possition.I heard the idle set screw should be around 6 out but im not 100% thanx sorry for the long post Quote Link to comment Share on other sites More sharing options...
SypherSlayer Posted June 2, 2009 Share Posted June 2, 2009 id say that its the brake booster as well because you only need a small leak in the vac lines to have a problem. my 96 gmc truck just had the same problem. i had a leak in my booster and it caused the truck to run kind of crapy but not horribly. without the cpu to compensate it probably would have run much worse. you'd be best to replace the booster asap. one because it is likely causing some or most of your problems and 2 it could go out and trust me its not fun trying to stop a vehicle which out a working booster. (my trucks booster went out and good god that sucked) Quote Link to comment Share on other sites More sharing options...
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