HICKL Posted November 22, 2002 Share Posted November 22, 2002 I have a stock (for now) 76 280. Sometimes, my tach will start jumping around erratically and basically double the actual RPM reading. I can be going down the highway and all of a sudden my tach reads 7000 rpm. I push in the clutch, kill the motor and start it back up and it fixes it. I've gotten so good at it that I don't even loose any speed. When it happens at idle, the motor lopes/lunges really bad. At higher rpm it doesn't seem to effect running. It seems to do it more often on really hot days. Any ideas? Thanks Jeff Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 23, 2002 Share Posted November 23, 2002 Try putting a load on the tach i.e. headlights to see if it still jumps. Hope someone elso jumps in here I am no expert, however, I installed an alternator on my boat and in the data sheet it mentioned that if the tach jumps, "just put a load on the circuit to correct". Steve Quote Link to comment Share on other sites More sharing options...
HICKL Posted November 26, 2002 Author Share Posted November 26, 2002 I don't think its that simple since it effects the way the car runs. Thanks for the input though. Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted November 26, 2002 Share Posted November 26, 2002 Sounds like your pickup coil inside your distributer may be going bad, here is how to test it and find out. Take off your distributer cap and pull the rotor off, then locate the connecter beside your distributor where the wires connect to the distributor. Disconnect the wires at the connection, using an ohm meter check the resistance of the wires coming out of the distributor, right this number down. With the ohm meter still connected use a halogen work light (or any other hot lamp) and heat up the top portion of your distributer and watch to see if your resistance changes, then after the thing is hot tap on the side of the distributer with a rubber mallet or something similar that will not damage your distributor, again watch for a change in resistance. If you see any eratic or obvious changes in resistance your pickup coil is bad and needs to be changed. Changing the pickup coil can be done yourself but it is not a job for the mechanicaly timid. If this is your problem it will only get worse and your car will start to die on you for no apparent reason, what is even worse is when you take it in to a mechanic they will not be able to find the problem and will probably just replace your entire distributor and charge you an arm and a leg for all there trouble shooting time. Good luck and if that is the problem and you would like more details on fixing it yourself just let me know. Dragonfly Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 26, 2002 Share Posted November 26, 2002 DragonFly... what lower radiator hose did you use on your Griffin radiator????? Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted November 26, 2002 Share Posted November 26, 2002 TomahawkZ I wish I had a Griffin radiator, what I have is an aluminum radiator from a Fiero, for both upper and lower hoses I had to use a generic hose (corigated with spring inside) and hand shape it to fit. You can buy the generic hose in almost any length you want and almost any diameter you want. Dragonfly Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 27, 2002 Share Posted November 27, 2002 Hey, you mean to tell me someone else has the erratic tach also? I put my MSD box and my Auto Meter tach and speedo in and mine kinda does the same thing... when first started the needle jumps about 2000 rpms and then goes away when it warms up a bit. Also, at about 3000 rpm it will jump around 500-1000 rpms. You can hear the miss slightly and every once in awhile it misses really bad when applying heavy throttle, but not always. The problem has not gotten worse but it is a little frustrating sometimes. Do you boys think I have the same problem? Will your test procedure work with my MSD? Thanks for the help!!! Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 27, 2002 Share Posted November 27, 2002 I resurfaced an old post of yours (aka Miles) inquiring about a lower radiator hose for a Griffin and was given the answer that a Napa 8948 hose would fit and a 1973 Monte Carlo 350 upper for the top hose from my donar. I was just curious if you found a lower radiator hose for a Griffin since the Napa requires a spring inside and is still a little "bent" in the application. I may add in a short section of larger diameter spring to fill in the walls on the bent section since a full length large diameter spring cannot negotiate the curves in the hose for any distance like the small diameter spring does.. Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted November 27, 2002 Share Posted November 27, 2002 There is a guy on here who is also named Miles and uses his name in his handle, I remember seeing the post you are talking about, but we are two different people. I have to admit that when I see him post it throws me for a loop at first then I'm like "oh yea thats the Miles with the V8 Z". Dragonfly Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted November 27, 2002 Share Posted November 27, 2002 Wow.... somebody that actually lives near me. I've had a similar problem w/ mine expcet the needle would stick at 3k till the engine got to 5k then it would jump back up. did it all summer long, doesn't do it anymore though? good luck Ed (woodlands, TX) Quote Link to comment Share on other sites More sharing options...
HICKL Posted November 27, 2002 Author Share Posted November 27, 2002 Dragonfly, thanks for the input I will test it this weekend. I ain't scared of mechanican! Nismo, drop me an e-mail, maybe we have some parts to swap. I probably live about 10 minutes from you. Jeff Hickl Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted November 27, 2002 Share Posted November 27, 2002 The procedure I outlined will work for any vehicle that has pickup coil in the distributor. If the problem is only with the tach and you are not having trouble with miss firing, bogging, etc. the problem is probably in your tach or the wiring to it. A bad pickup coil will cause erattic tach behavior but will also cause erratic missing, bogging, engine dieing while idling, and other various ignition related problems. An MSD uses the same pickup coil that your stock ignition system uses so the procedure is the same. Dragonfly Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted November 28, 2002 Share Posted November 28, 2002 I had a similar problem with the tach in my 73. It would jump all over the place when the weather was warm, but on cool nights, I had no problems. It was steady as a rail. Finally, it annoyed me enough to do something about it. I replaced the tach...no more problem. Quote Link to comment Share on other sites More sharing options...
Guest silverbullet Posted December 2, 2002 Share Posted December 2, 2002 If you are having problems with missfiring or the tach is bouncing all over the place it sounds like Dragonfly is on the money but if your tach just kind of pegs out once in a while like mine does(77-280) I remember reading a post on another site where someone was saying that the old mechanical voltage regulators will just sometimes have a voltage burp and I think that is what is happening to mine it has only done it about 3 times in the ten yrs. I have had it, just one quick peg out and then all is fine Quote Link to comment Share on other sites More sharing options...
Guest questhe Posted December 19, 2002 Share Posted December 19, 2002 Hi all, On my 82, I am now getting engine cut-outs, usually when the motor warms up. I have to turn the key off and the back on if I am at a light. If I am under power, the engine lurches on and off. The tach also dies with the engine. So far I have replaced the ignition relay. The wiring diagram shows the circuit going through the coil to the tach, so I was going to change the coil and cap next. Since I have 100K on thos components, I figured it wouldn't hurt to go to accel coil. Anybod have recommends on that? Anyways, I recently rebuilt the distributer, the plastic spacer went to **** . I fixed it by turning the metal ring upside down, almost made up for the whole space. However, There is a bit of slop in the way the coil ring sits. So I guess I have to do the pickup heat check. Sounds like a bitch. Is there a good source for the part if it turns out to be bad? Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted January 24, 2003 Share Posted January 24, 2003 Check your fuel delivery make sure you pump is good. Quote Link to comment Share on other sites More sharing options...
pallnet Posted February 23, 2003 Share Posted February 23, 2003 i also have the "MEXICAN JUMPING TACH" i have found the problem and i think i will just replace it and be done. the tach signal is a push on wire that goes on the back of the tach, it gets a little corroded or loose with time. i can pinch it and it will work fine then if i just twist the connection it starts jummping around like a cat on a hot tin roof. i bought a new tach today and it will be going in in a day or so. i'm running MSD and have been drawing the signal from it to run my stock tach. i changed the connector and it worked great for a while. good luck.. pallnet Quote Link to comment Share on other sites More sharing options...
280Zen Posted February 26, 2003 Share Posted February 26, 2003 My tach doesnt jump but the larger needle on my 83 280zx fuel gauge jumps all over! the smaller 1/4 tank gauge works great though Quote Link to comment Share on other sites More sharing options...
DarrellBuddy321 Posted June 4, 2005 Share Posted June 4, 2005 hey guys i know this is an old topic but i had a question... I just installed my 6al on my 280zx and im using the tach adapter and everything and my tach needle jumps also. Now you guys said to check the wire connected to the tach. Well why would the tach wire go bad allof a sudden when installing an msd? Well anyways what other solution have you guys come up wiht? Quote Link to comment Share on other sites More sharing options...
VinhZXT Posted June 8, 2005 Share Posted June 8, 2005 280Zen, The resistor (sensor) inside your gas tank has build up on it. This usually tells you that you have rusts in your gas tank. Open it up and check it. Darrel, I have this same problem on my ZXT and I just called the MSD Tech and they said to put a capacitor inline to the power wire for the MSD and the Tach Adaptor. It's the current being drawn from your tach adaptor that makes the tach jump. Well mine is jumps down instead of up. Quote Link to comment Share on other sites More sharing options...
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