I am leaning towards the bad speed sensor. I have a bad one because it kept messing up. I sprayed it with Wd-40 to try to clean it. **Unplugged it from tha tranny and reinstalled** and it stayed at zero then. So that was my problem but at 100 dolalrs, I will pass for now.[:'(]I got more important issues/mods/repairs to deal with than a speedometer. I got a fuzz buster and keep my speed limit reasonable when driving so Ill be good for a while.

 

The ECM arrived today from Eckler's. It does not come with a PROM cover plate, nor does it come a chip. The first thing I noticed thisECM didnot appear to be an AC Delco remanufacture like the one I'm replacing in my 1986. My AC Delco has a sticker Identifiy it as an AC Delco Remanufacture with the correct part #. The one I got from Elecker has some generic sticker indicating "Engine Control Computer-ASE" . From the outside of the ECM the Eckler and the AC Delco look Idencial except for the stickers mentioned eariler.

Inside the ECM was a different story. The AC Delco Remanufacture's circuit board has much morecoating over the board. The Eckler circuit boardcoating looking much more uniform and clear.

I don't have time to mess with it until later, but will try to get it done by Saturday. I'm kinda thinking the ECM will not fix it. I'm leaning towards a rebuilt Digital cluster. Shouldknow for sure soon enough.

The more I get to work on this car, the more I understand how it all works. Thiscar dyno'd at 255hp. It has a Hypertech 180 degree chip/thermostat. The injecters were replaced about the same time. Other than that...its a stock Z51 4+3

It may not keep up with the new vette, but it will sure blow the doors offits competion in 1986, and that's what really counts in the end[:-]

 

Your L-98 makes that much ponies and its almost stock?????????????????????????????????????????? or are you talking about a L-T1 or something else.

 

Well...........Ironhead, did you fix your speedo problem?????????????????????????

 

I installed the ECM on Saturday. The new ECM did not fix the problem, and made the car run worse. I'm getting a code12. I suspect it is a bad ECM, since when I put the original ECM in, the car runs great...just get the code 24 after about a half mile.

I'm going to call Eckler and see if I can get a refund.

Next step is to pull the instrument cluster and send it in for repair.

 

Well, that stinks. It's got to be the speed sensor, speed sensor wiring or something in the cluster. That's what I believe it's narrowed down to. Keep me posted. I am still chasing the short that blow's my tailight fuse but think I've found it. I found a post from a guy on another Corvette forum that was having the same problem about a year ago and emailed him. He said his short was coming from the steering column, fixed it and no problems since. That makes since because a few times I blew the tail light fuse it was when I hit the blinker, on the column of course. Wonder if anything in the steering column could be causing the speedo problem I have also. I know the cruise control goes thru there, could be related to the same problem but probably a long shot. Anyhow, plan on tearing into the steering column in a week or so.

 

Just got off the phone with a guy named Gene at this place:
http://www.corvettedashclusterservice.com/

He told me to pull my insturment cluster (IC)and send it to him. He indicated that the power supply for that portion of the IC controlling the speedometer signal input is bad. Theyrebuild them, so you get your original back....in like new condition. $185 + $18 shipping=$203.

Now to get that ECM back to Eckler

 

IRONHEAD, did your 4+3 overdrive stop working when you speed was going down to "zero" also??? Just curious, please let me know about the speedo cluster. I'm chasing a different gremlin now, a blow tail light problem I believe to be coming from the steering column. After that, then onto the speedo problem.

Then polishing my rims

Then replace all door/hatch seals

Then getting the parking brake working

Then getting my A/C working

Then painting my mirrors that turned from red to purple

Then a new exhaust system

Inbetween all of this..............driving the crap out of it.

 

Myoverdrive stopped work when the speedometer went out. The Overdrive relay will not set if the Speedometer is not sending feedback to the ECM.

#1 problem when troubleshooting a light problem are usually the switch (Door switch...etc...) or the bulb housing dirty.

 

Thanks for the info, when is your new/upgraded cluster due? Talk to you later.