tomcamaro97

I was kinda working on a different thread, but figured ide start my own.

86 4+3 z51

So Heres my question.. my car is popping code 24, VSS error, which from my readings, could be the sensor or the wiring..

Only symptom is the car stumbles really bad, to the point of not being able to accellerate over 2500.. (atleast i assume its a symptom)

speedo is fine, Engine runs great in neutral.

Other notable items: recently replaced entire fuel system.. fuel pressure is steady, unless i goose it then it drops, but will come back up if i hold it there, it seems to increase rpms fine/with power in neutral.

OD button doesnt seem to work.. tried hitting it a couple times, no lights came on, i dont really care about it working or not, for now. not sure if related?

i plan on checking out the VSS shortly ( i know how) , could a bad vss be causing my stumble issue? just seems weird it could cause such an issue.

and if so , i know the vss are hard to find, whats a reasonable price for a used one? or does anyone know if new ones are available anywhere?


thanks all. appreciate the help

THE 383 admiral

they claim. your engine. will run just fine without the VSS. my previous well built TA with a HSR intake. and my tune. about 430HP. the VSS died. if i cleared the code. the engine started and ran perfect. code hit instantly. Then ran like a blown engine. the T5 VSS for example. is about extinct. I parted everything OUT.

Benny42

When i did the T56 swap into mine, the Dakota Digital speedo box was the last part to come in. I just had to drive it before the speedo worked. The car ran terrible, died at every stop and bucked at any throttle change while rolling. I installed & set up the speedo box and it was like a different car. All the issues went away. YMMV but it may be all that is wrong with your car.

WVZR-1

If the speedometer works "consistently" and is correct then it could be assumed I believe that the VSS is fine. In the early cars the cluster/speedometer is the "FIRST STOP" so I'd be looking at issues with cluster/speedometer circuit to ECM resulting in the DTC.

Do you have the FSM? You need this to continue diagnostics.

tomcamaro97

the speedo works consistantly, and is correct, also i took a volt meter to the VSS, and as my speed increase the voltage increases. also checked the wires aroudn the tranny , look fine to me.

I dont have the FSM, or even know what that is, service manual?

I have also noticed my alternator is not working well.. the dash shows im running at 11.5 volts... so i ordered a new one that will be here in the next day or two, i wonder if low voltage might be causing this code... as i know low voltage causes all sorts of crazy stuff.

antfarmer2

FSM factory service manual........ fix your voltage.

tomcamaro97

oh i will....

it wasnt coming up before..and didnt think it was an issue, but i notice the voltage on the dash comes up as an issue below 11.5 volts, so im guessing its slowly blead down.. as soon as i saw that i ordered a new alternator instantly... (after doing some checking of course)

WVZR-1

OP - if the alternator is the original I'd consider having it checked by a "local" shop and maybe consider having the entire electrical evaluated using correct diagnostic devices. A bench test at an AP Store isn't generally considered an creditable evaluation. I wouldn't just throw an alternator at it until it's proven to be a problem. How old is the battery? Have you checked all of the cables and the quality of the connections.

FSM - Factory Service Manual

antfarmer2

Ebay has the red two book set for 60 bucks.

ToniJ1960

I don't know if 86 and 84 were different in this regard, I can say I drove my 84 over a year with no vss attached as it was damaged when I bought my car. I purchased a gps vss and built my own speedometer and odometer, I just haven't fed the signal back to the ecm yet. But I can definitely tell you it doesn't make my car stumble run rough stall etc.

It runs fine open and closed loop. Didn't make sense to me to spend a lot of $ on an 85 mph speedometer in my Corvette

Klondike

Low and unsteady voltage will cause all kinds of problems. The computer looks for very specific voltages for all kinds of sensors. If they vary from what it thinks those sensors should be, it tries to correct those low or high readings. The pulse width for flow for the injectors and the O2 readings will wander and the computer will be trying to correct these things without enough steady voltage. You can't walk straight when you're drunk and low voltage and poor grounds makes your computer act drunk! Fix your alternator and check your grounds and I'll bet most or all of your problems will clear up.
Your OD button is connected through your computer and throttle position sensor, so it might clear up too.

Kevova

The dash reading 11.5v doesn't always mean charging system failure. You need to check voltage at battery along with alternator output. Some auto parts store will test charging systems for free. If charging is 13.2v and cluster only has 11.5v you have either a gauge issue or high resistance on feed or ground circuit. If speedo never stops working VSS is ok, problem maybe in cluster, circuits to ECM or ECM. In DIY section at batee.com is wiring diagrams of cluster circuits and vss to ecm. If charging system is working (11.5 is not )I would check voltage at different fuses in fuse box to see if voltage is within .2v of battery. If they are then I would look at grounds. There has always been something about code 24 and driveability mostly on EFI. I figured it was to discourage disconnecting speedometer in an effort to keep miles off odometers. Last thing are there added electrical accessories?