Drove over 200 miles today, and when I got on the highway I noticed I was 60 miles per hour, and my tach said 3500 rpm It usually revs around 2700 rpm at his speed... so I floored i to see if my clutch was slipping.... and she just picked up speed... no slip but at 70mph the tach read 40000rpm...usually 3k So later on, Im sittin at a stop light and I look down at my tach, and the needle is bouncing from 500-1200 rpm before it finally settles in at 1200, with no audible change from the motor.
Anyone come across this type thing before??? Ive seen when tachs have a bad wire, or faulty connection before... but they usually read less than the actual rpm... not more... from what Ive seen tho...they do bounce in and out...but not just at idle...all the time. So whats goin on here? I'm assuming its some sort of electrical problem....anyone got an easy fix...other than just forget about it?

 

Samething happend to my truck (last weeks my girlfriends did it too). But the tach would sit at 0 at stop lights.

clean the igniter ground and the battery/body ground You will be good to go.

 

Ill give it a shot...they should be all set tho... I already did the ignitor...maybe thats the problem....

 

I bet its the problem

 

I have the same issue.
At an idle mine bounces from 1000 to 0
usually settles at about 1200.
I drive up the mountain everyday and that means the tach is usually moving the whole way (Darn Toyotas)

usually bounces between 3-4 with normal driving.
Mechanic said it sounds like a loose connection from the signal wire, or a bad signal wire.
Doesn't bother me too much it, But it's annoying and is on my fix-it list.

 

clean the grounds.. dooo it! takes 10 mins

 

Damn those Japanese can BUILD a valve train!!!!!

 

If this is the OEM tach reading wierd, the first thing I'd do is grab another tach and hook it up and see how they compare. If the OEM bugs out and the other doesn't, I'd suspect something wrong with the OEM and/or the wiring. If they both go buck nutty then I might start looking at the igniter.

 

buck nutty???

 

Did he mention if it was A/T or M/T, and if it was cold out? Because my 22r tach acts up when its below 0 degrees (common in Montana) and its M/T and carb'ed.

 

ya...its 5spd...(hence the clutch...lol), and it was super cold out yesterday (10*f, with a nasty wind). I got to thinking....I cleaned up all the grounds and such, a few months back...I bet somethin is loose, or more rust has occured...I swear... with this salt/calcium combo, I can actually watch the truck rust.
Ill investigate this a bit more later today....thanks for all the tips, and Ill report my findings.
BTW.... This only happened for a short time... after I got off the highway, and shut the truck off for 3min, it was fine the rest of the day.

 

my diesel hilux needle is a bit jumpy too.. only notice it when i first fire it up and put it into idle up mod.. then when i go to normal idle mod it will drop and shake a bit..
but my diesel doesnt have a ignitor

 

Pretty sure automatic trans have clutches too, and also you said "so i floored it to see if my clutch was slipping" how would that tell you if clutch was slipping (shifted first? then floored?) this is why i asked if it was a AT or MT, because auto you could floor it and being and auto it would shift on it's own ( to see if its slipping) anyways hope you figure it out.
ps shows you have 2MT and 1AUTO on ur signature. (another reason i asked)

 

I suppose there are lots of things on cars and trucks that can be called a "clutch" and even some things in the automatic transmission. But, usually when someone talks about a slipping clutch in the manner that Team420 did, they are speaking about the thing that bumps up against the flywheel and has a pedal to actuate it. I know that automatic transmissions don't have these cause I threw my left hip out slamming around trying to find the clutch pedal on my wife's Pathfinder, which has an auto transmission. Go to shift into drive and I put on the brake and started searching for the clutch pedal and about an hour later my wife comes out and says it doesn't have one. Who knew?

 

true, auto's do have "clutches", although... I usually just refer to them as friction plates.
flooring it would have told me if clutch was slipping, if (while in gear of course) the rpm's increased with out my speed increasing.... like i said...was on highway doing 60... dont know about the rest of ya... but im in gear @ 60mph.
Sorry for any confusion, and thanks for the tips!