Hey guys, I finally got my 84 Corvette to idle without stalling. Quick run-down, it's a 50k mile 84 Corvette that basically sat for 6-7 years ... outside, after the owner died. I'm making it a project for my daughter to work on (she's restoring her Fiero right now, but I'm doing some leg work and trying desperately not to fix it so she'll have to do it... but it's killing me, haha).

So, I added some fresh fuel and some Seafoam. I plugged a couple of very obvious vacuum leaks (I will probably tear it all out and have her replace all the vacuum lines). Now it idles at a calm 800 rpms. I let it idle for a good 15-20 minutes, and I'm pretty happy with it so far. I checked the error codes, and there are two codes I'm getting:

33 - MAP SENSOR
42 - Electonic Spark Control

(Note, I referenced the codes from this link here that I found in search: https://www.corvetteforum.com/forums...s-84-96-a.html)

MAP sensor is easy... probably just a vacuum leak. But ESC? This is a hard one. I just assumed ESC is part of the ECM? What exactly could it mean that ESC has an error code? Is this something I have to replace, what exactly is it, if it's not part of the ECM? Does it just mean it's having issues with the distributor?


Thank you!

Todd

 

Ok, I just did another search... I had no idea there was a separate ESC module on these Corvettes... it's a little module... so weird. Does this thing control timing? Does it basically handle timing advance? I wonder if this can be adapted to other engines that are carbureted, but where it would be nice to have spark timing / advance. That's wild...

 

It's located on the passenger side, just underneath the RH Hood pin latch housing...right by the windshield washer fluid reservoir.👍

 

The ESC Module is only used to retard spark if the knock sensor detects engine detonation. Engine spark timing is controlled by the ECM through the HEI module in the distributor. I would highly recommend getting the factory service manual (FSM) as it gives detailed operation information and troubleshooting. Attempting anything else is a waste of time and money IMHO. Manuals can be found on eBay and other sources. Digital copies are also available if you don’t want to spend the money on a hard copy.

However, in the interim searching here on the forum can yield a tremendous amount of good information as I guarantee someone else has had all the issues you are describing.

 

Here's probably a few too many, but hopefully some pictures of information you will need to diagnose your issues! Click on photos for better resolution! Most are in order, mixed up a couple....take note of page #'s! Good luck👍

 

Ok, that makes a lot of sense then. I know back in the day, they had an ESC system for carbureted cars... somewhere around 1977-1980, before they started implementing TBI, etc. But it was blowing my mind to think they had a little ESC system in that little module. Makes total sense what you said.

I'm embarrassed to admit that I actually already have the factory service manual (or as this one is called, the Shop Manual). I bought it from The Motorbook Store. I'm so used to asking questions on the forums, that I completely forgot I had it. I use them religiously on my Fiero, but have to use the Parts Book for better diagrams.


Thank you! I just found it... it was connected, still the GM one. I'm wondering why it gave that error, but I went ahead and ordered a new replacement GM one from Rock Auto, so we'll see.



Thank you SO much for taking the time to take all those pictures, and post them for me. I realize how much of your personal time you took to do that, and I really appreciate it. Thank you so much!

Is your factory service manual the original one? I noticed it's all in a three ring binder! I'm jealous!

This Corvette is going to be a project for my daughter that we're going to work on together. She's almost done with her Fiero, and I'm trying to diagnose a few things before she starts tearing into it. She has a YouTube channel (which she hopes will help her get into a good school), and next week she starts working on the Corvette, but we were just waiting for some Corvette shirts to come in before she starts working on it. We have everything needed for a complete tune-up, so it's going to be pretty exciting to be able to start driving this beast around. I'm really looking forward to it. It sounds so awesome at idle... I don't know what exhaust system, is on here, if it's stock or not... but we're going to end up going through the ENTIRE car from front to back. This engine only has 50k miles on it, so I'm debating whether or not we even want to pull the motor... I think it depends on the condition of the transmission. The car is very complete, but someone who didn't really know how to work on cars started to hack it up.

When she's done with it, it'll look as good as this engine bay does... she's really particular about making everything look as stock as possible, and painting every little thing... she even remade that little sticker on the air cleaner by finding all the pictures she could of factory Fieros from the 80s, haha...





Anyway, thanks guyss, I really appreciate it. MAP is fixed now... (vacuum line was unplugged), so when the new ESC module comes in, I'll test it out.


Thanks!