TexasStyle280z Posted April 14, 2009 Share Posted April 14, 2009 hey all, im new to this forum and im having an issue. ive got a 77 280z and am in the middle of taking care of the machanical issues. the one that i still havent been able to figure out is that i cant get the rpms above 3000. and it actually takes forever to get from 2500 to 3000. i can put the peddle to the floor and nothing happens. it cant be anything to major because the engine actually runs great(real smooth, sounds good & gets descent mpg's). so far ive. replaced all sensors on thermo housing. new plugs and wires. new fluids and filters. checked continuity of throttle valve switch. cleaned throttle body. checked throttle linkages. checked all injectors(not replaced yet) any ideas. ive seen other posts on other forums of people having a similar problem but i havent gotten any responces from them on what there solution was. any help would be greatly appreatiated. Quote Link to comment Share on other sites More sharing options...
m4xwellmurd3r Posted April 14, 2009 Share Posted April 14, 2009 how do your boots look for the AFM? (have you checked to see if your AFM is correct?) what kind of fuel pressure is it running timing is set right? is your exhaust crushed? Quote Link to comment Share on other sites More sharing options...
boardkid280z Posted April 14, 2009 Share Posted April 14, 2009 Does your car still have a CAT on it? It's not clogged is it? Does the floor get hot? Quote Link to comment Share on other sites More sharing options...
TexasStyle280z Posted April 14, 2009 Author Share Posted April 14, 2009 it does have a cat, and i never thought of checking it( i will do that this weekend). the floor does not get hot, there are no crushes in the exhaust and the timing is correct. i will also be replacing all the fuel lines this weekend so i will check the preassure then. the boots on the AFM are new. i have visually checked the afm but am not sure of how to check it beyond that( how do i go about that). thanks for your suggestions, i'll post my results soon. Quote Link to comment Share on other sites More sharing options...
RUZN Posted April 14, 2009 Share Posted April 14, 2009 I'll check what the ohms are supposed to be on AFM but you can open the Little Black door on it. Inside you'll see a Potentiometer, theres a small Brass (gold colour) screw on the upper left side that has a Square type press that locks the big gear from moving. you can loosen the screw *WHILE HOLDING THE GEAR FIRMLY* with your other finger. I think Back is more fuel and forward is lean. you can try this as well just move it like 3 teeth either way but mark is position is the glue on screw is not there. This solved a drive isssue on my 81 280zx one day. Some reason it just didnt liek the mixture anymore... other than that I didnt see you mention plugs. check em and Spray wire with mist of water see if there is arcing. hmm... other than that if your TPS is working and all vacuums are good then not to sure........ if you can see down Sparkplug hols if its super shiney down in there you might have coolant going into cylinders.. could do a leak down but I doubt that is the problem..... maybe Electrical connector is corroded on TPS or Battery post or Alternator. Check voltage from alternator if you take negative off while car is running and it dies its alty. can be done without volt tester.. My 2 cents... lol Quote Link to comment Share on other sites More sharing options...
boardkid280z Posted April 14, 2009 Share Posted April 14, 2009 I'll check what the ohms are supposed to be on AFM but you can open the Little Black door on it. Inside you'll see a Potentiometer, theres a small Brass (gold colour) screw on the upper left side that has a Square type press that locks the big gear from moving. you can loosen the screw *WHILE HOLDING THE GEAR FIRMLY* with your other finger. I think Back is more fuel and forward is lean. you can try this as well just move it like 3 teeth either way but mark is position is the glue on screw is not there. This solved a drive isssue on my 81 280zx one day. Some reason it just didnt liek the mixture anymore... This doesn't sound like a problem with the AFM being out of adjustment, I wouldn't make any adjustments there, until you've checked everything else. Quote Link to comment Share on other sites More sharing options...
RUZN Posted April 14, 2009 Share Posted April 14, 2009 Just something to try =-) Cause if its not reading Airflow you aint getting those RPM's up =-) easy to put back tooriginal place after if it dosent solve the issue yes =-) Quote Link to comment Share on other sites More sharing options...
m4xwellmurd3r Posted April 15, 2009 Share Posted April 15, 2009 it's easier to just open it and while reving the engine, move the flap one way or the other to see if your issue is a condition of being too lean, or too right (But do not adjust it if it has not been tampered with) that's what I do on my Z. most of the time, it's simply a problem of corrosion on the connectors. if your throttle position switch is busted (which is unlikely, but the wire itself could break) the engine will stutter and stumble very badly trying to get those rpms up, (and it will not be happy at all) Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted April 15, 2009 Share Posted April 15, 2009 Engine won't rev huh? Did you power wash the engine bay? If so, you could have water in the afm electronics (moisture is enough to mess it up) Dry it out with a hair dryer. Do simple stuff first. Check grounds and wire connectors. Don't just look at them, unhook, clean, and reattach a use a bit of dilectric grease on the connectors. Keep us posted. The more details the better. Scott. Quote Link to comment Share on other sites More sharing options...
TexasStyle280z Posted April 18, 2009 Author Share Posted April 18, 2009 ok, so i was wrong about it having a cat. what i thought was the cat was the ressonator. i took it out to inspect it and even though its as old as the car and rusty it seem fine(wide open, no restrictions), so the exhaust is flowing smoothly. i adjusted the gear in the AFM(in both dirrections, 3-4 teeth each way) and there was no difference, rpms still topping out around 3k. the glue that is supposed to be on the AFM adjustment screws was gone so its safe to say that the previous owner had made adjustments. there is a whate mark on the gear(shown in pic). does this mean anything. is there any way of telling how it was set stock. thanks for the help so far guys. Quote Link to comment Share on other sites More sharing options...
m4xwellmurd3r Posted April 19, 2009 Share Posted April 19, 2009 my afm has the same white scratch from the hold down piece scraping on it when I would adjust it. fire the car up, go full throttle till it stops reving (which for you is 3000rpm?) and just play with the flap. moving it to the left gives more gas, and to the right gives less gas. if it has been played with, it looks REALLY freaking lean Quote Link to comment Share on other sites More sharing options...
woldson Posted April 19, 2009 Share Posted April 19, 2009 May seem over easy, is your throttle opening all the way? Quote Link to comment Share on other sites More sharing options...
TexasStyle280z Posted April 19, 2009 Author Share Posted April 19, 2009 the throttle is opening all the way. the flap in the AFM is also opening all the way. timing is dead on and i just put brand new plugs and wires . i spent today adjusting the AFM to different settings(turning the gear) and it had no effect on the problem.. im going to order a new throttle valve switch, and air pressure regulator this evening. i'll let you know of any changes. Quote Link to comment Share on other sites More sharing options...
m4xwellmurd3r Posted April 20, 2009 Share Posted April 20, 2009 another thing it could be, a simple clog in the gas tank or in the fuel pump. my car will basically do that, except it also starts hesitating when it gets really bad. instead of having to constantly buy new filters I got a simple fuel injection filter that has a metal screen in it so I can just shake out all the rust flakes that build up in there. Quote Link to comment Share on other sites More sharing options...
woldson Posted April 20, 2009 Share Posted April 20, 2009 Pop the throttle position switch cover, (since your getting a new one;)) and see if it is moving through the contacts properly. Quote Link to comment Share on other sites More sharing options...
TexasStyle280z Posted April 23, 2009 Author Share Posted April 23, 2009 i have checked the throttle position switch and it seems fine. i do have a question that has just acured to me. im fairly new to doing this amount of mechanical work(usualy im just a body and paint guy) so this may be a dumb question, but here it goes. so you all know what the problem is(i can barely get the engine to rev up to 3k) i was in the working on it the other day and while reving the engine i noticed that while in neutral it will rev easily up to 6-7 k. so my question is that if it was a proublem with the engine or its sensors wouldnt it also be affected while in neutral? could this possibly be a clutch or tranny proublem? please educate me thanks for the help Quote Link to comment Share on other sites More sharing options...
MONGO510 Posted April 23, 2009 Share Posted April 23, 2009 check to see if your muffler is plugged up. If it is it will hiss real bad at full throttle. Quote Link to comment Share on other sites More sharing options...
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