Hows it going? Been reading posts for about 2 years, never had to post but this one has stumped me.

1989 2.8 Electronic speedo

Speedometer jumps (from speed to 0 to 30 to 0 .....) when I am off the gas. Most of the time jumps back to the correct speed when I get back on the gas. The odometer also stops when I am off the gas. Also if I am on a long trip say 30 minutes or more, the problem seems to go away

No code has been thrown (at least not 24, for some reason I got a 34 but thats a different issue).

I have read other posts about similar problems but cant seem to find the instigator. I have changed the VSS, and speed buffer, checked the wires (seem ok but I am not an electrician), inspected the gears in the transmission (seem fine). I checked out the wiring to the guages and nothing seemed loose.

Any ideas? I am hoping not the ecm but I really dont have the equipment or one to put in to test.

Also since it is not throwing a code would that mean the problem is between the ECM and Speedo? or am I thinking too much?

Thanks for any replies

 

I'm having the same problem, but im rockin an '84 2.8 camaro...
I keep reading somewhere that putting white grease on something will solve it... but have no clue how to do this... help please! thanks a lot.

 

I take it this is a T-5; that it does this the most in 5th gear; and works much better, maybe even works right, in 4th?

I've never heard of anything like that.

It's caused by the trans mainshaft moving away from the VSS a little bit, such that the gears no longer mesh.

Try a new extension housing bushing and a new driven gear on the VSS. You should be able to find someone in your area that has the tool to pull the bushing with the trans fully assembled and in the car.

A 84 car will have a cable-drive speedo, but the same things apply. Additionally, the chinesium housing that the speedo driven gear is mounted in, will wear out-of-round real bad, such that the driven gear loses contact with the drive gear. The cure for that is a new housing in addition to the above. The new housings that you get at the dealer are far superior to the POS that comes as OE in the car. The white lithium is for the speed cable itself; you slide the cable core out from the top, lube it, and put it back in.

 

-Same problem as shapeshifter- in a '84 Z28 but it only happens at low speed <10 mph. Can I change the cable and housing without pulling apart the dash?
Chinesium--

 

In your 84, if it has cruise control, you can lube the lower cable by taking it loose at the cruise regulator. If you don't, or it's the upper cable that's sticky, you'll have to get at it by pulling the instrument cluster.... not much of an ordeal. I can swap a cluster in about 10 minutes in one of these cars.

 

I'm not sure if this changes anything but... When i turn my lights on it gets totally inaccurate, and my tac redlines lol...

 

Could be the alternator going out on you.

 

Brand new alternator in it...

 

RB83L69- actually it will do this at low speeds also.

It will do it at pretty much any speed. Between my house and work I do about 30-40 at it fluctuates pretty bad when Im off the gas.

Dont think this makes a difference but it is an Auto trans.

Thanks for the replies

 

"Fluctuating" usually means that the cable needs lube. So if your car has a cable-drive speedo, try that. Also, if it has a mechanical cruise, it can make the speedo bounce, if it's sticky. You can spin the part the cable goes into by hand and tell if it's OK or not.

 

My kingdom for a cable speedometer.

Unfortunately mine is an 89 and is eletronic

 

this does not sound quite like your problem you are describing but, I will throw it in for the others reading, the wire harness clamps that mount to the top of you bell housing are real close to the electric speedo wires from the sensor (drivers side) after trans work the clamp can get position real close to the speedo wires and the main wire loom and rub through causing the speedo to turn off and on. its just some thing to look at if the speedo seems to stop and start and everything else checks out hope this helps some one out.