zilla24

Hello all
I am new here and desperately looking for help. After reading some of the other threads I figured I can find some good help in this forum so here I am.

I have a 1993 LT1 my wife and I bought about a year ago. Now its time for the problems to start I guess.

The car will just shut down while driving. It runs great and then will just turn off. I pull over and wait a moment and it then starts right back up. I am mostly a Harley mechanic but have some car experiences under my belt. (mostly pre-electronic controls but I am no dummy) Not sure where to start and looking for some assistance as it is a bit frustrating.HELP!!!

I also noticed that I have the selection (green) indicator light on the climate control blinking and today when it shut off the LCD for the climate control went to a dash and line _ _____ (basically blank)
and nothing worked. I turned the car off and re-started it and was back to a normal readout but still had the flashing light. I was looking at some suggestions in another thread (ECM Crapping Out?) According to what I read in there I should be hunting down a possible bad ground? I am going to try and locate the bundle of grounds located near the oil filter / bell housing?? and make sure they are all making good contact. Could the shutting off and the climate control be related?

There is also an oil leak on the drivers side at the rear of the engine that runs down onto the driver side cat. Don't know if the oil leak is a contributor to this. Cant see where it is coming from exactly. Almost looks like its coming from the head.

Yes I have some work to do but we love this car and want to get it right so we can enjoy it. My wife loves driving it and I don't want her stranded somewhere.

Repair history since I have owned the car:
Replaced the Optispark unit
Ignition Module
Coil
Water-pump
Brake Booster
Fuel Filter
Various vaccume lines

theadmiral94

Hi Zilla24,

congrats on your somewhat new-to-you Corvette and welcome to the forum, lots of great info and great folks which enjoy helping others.

If you don't have a set of FSMs, get them, invaluable.

re: just shuts off -- sounds like the ICM (ignition control module) or the Opti -- could also be the ECM. What brand ICM and Coil and Opti -- as folks have had problems with non-ACDelco ICMs and Coils and problems with Opti no matter what brand...

Have you pulled the codes (paper clip method)? any codes? If not tried to pull them, do a search, info on how and what they mean all over.

re: climate control light blinking -- usually means it has an error code, do a search to find procedure -- could mean the freon (unless converted, it is NOT r134a).

re: Oil leak on driver side rear -- could be the valve cover, head, or the oil pressure sending unit(s). If 93 is like my 94, will have a 'pipe' sticking out of the rear of the head block just to the driver side of center, and just below intake -- then connected to it are two oil pressure sending units, one longer for fuel/oil pressure, the other one (short) is just for the 'check gauges' light on the dash.

The oil leak there could reach the major ground point (driver side bell housing bolt) and compromise those grounds.

zilla24

Thanks for some good insight Theadmiral94. I have ordered my FSM's and anxiously waiting for them to arrive so I am not flying totally blind. They are not cheap! I thought my Harley manuels were alot. Noy anymore.

I have not tried to pull codes yet. Think I will try looking at that today.

I went after market on the Opti and hope it does not turn out to be that. That was a heck of a job. Would that have a specific code?

As for the ICM I did not have to change it but did really just to have a spare. Changed back to the original and it does the same thing. Have not checked the coil yet.

As for the climate control light I will check the freon today as well and am going to go search out that leak where you mentioned it may be. Hope it is that simple.

Last time I drove it, after about 3 miles it shut off at a light. Would not start right back up. Had to wait a few before it would re-start. When it does shut of it is like turning off the key. It just "bam!" stops. " Without the bam of course.

I will let you know what I find and Thank you!

LannyL81

I think the climate control error indication is separate from the engine stopping.
And from your description that the engine just stops, sounds like it is electrical and not fuel related.
Checking the grounds is the first place to start...and be aware that there are lots of them. Check for corrosion on the battery cables...pull the plastic boots back and take a good look.
There is a ground connecdtion on the back of one of the heads...not sure now which side. Going to be very tight getting into this area.

You might find the source of your oil leak while doing all of this as well.

AS far as the climate control...it may also be a dirty connection....but these controllers have a failure history. Take it out and clean the contacts and check for any failed solder joints on the internals.

Good luck and let us know what you find.

zilla24

Well here is what I have so far. As I am to understand it there are 3 Modules for codes? Remember I dont have my FSM's yet.(sorry)

Mod-1 Code H41 Loss of ECM serial data communications?


Mod-4 Code H16 Distributor Ignition System (Low Resolution Pulse)?
Left from when it went bad originally?

Mod-9 Code H72 This is tied to the Radio?
Which is bad and the tuner is currently on my bench.

Then after these show I end up with a 1.0 and nothing else happens so I take it I am done at that point.

So how can I clear these so I can see what codes come back?

hemivett

What are you using to read the codes. I cant remember what year they changed from OBD1 to OBD2. If its 1, then you should be able to disconnect the battery for 15 seconds, and they will clear. If its 2 then your code reader should have an erase button. If not, take it to O'reilly's, They will let you borrow there reader, and you can erase them. h

zilla24

Hello hemivette
I am using the "paper clip" method and seeing the codes on the speedo. I will try disconnecting the batt and see if the codes are stilll there.

Where is O'reilly's? They local to West Palm Beach?

Thanks

zilla24

Where are my manners?
Thanks for the input Lanny!

pcolt94

As I do agree with posts 2 and 4, if you have cleared all the codes, re-check to see if code 16 in module 4 returns. That would be the low resolution pulse from the opti which all timing for the spark and fuel injectors are being derived from. Without those pulses the engine will die.

The ICM is a much higher probability of failure that a coil and is characteristic of you problem and would be nice and easy if were the problem.

Also check you pin connections at the opti and other related ignition connectors for a corroded pin.

Another invaluable tool for the corvette is a fuel pressure gauge. Definitely a possibility the fuel pump could be causing your problem also. You may need to drive with it for a while to monitor the pressure to confirm or eliminate the pump.

As for a last but not final possibility would be the ECM. These items have been known to cause these problems and an assortment of other engine running problems. Sometimes heat is a can aggravate the symptoms and putting an ice pack on the ECM (under the hood) may assist in the troubleshooting.

Your 93 is OBD1 (OBD2 starts in 96) and has the convention plug which a parts store may be able to scan. But it will only look at the ECM, module4. The on board (paperclip) will look at all modules and will give you the same info on the ECM but will tell you about all the modules as well.

Get the code for your flashing LED to give you a starting place for the A/C problem. It is also in the FSM books.

http://www.corvetteactioncenter.com/...agnostic+Codes

Focus in on parameter "0" for the code.
(The rest are for diagnostics)

This will not relate to your engine problem. Is your A/C blowing cold now?

zilla24

Thanks Pcolt94!
I added 1# to the A/C and it is blowing cold and there is no flashing light at least right now.
I took another ride after clearing the codes and it shut off again. Started back up after a couple min.
I got it back home and checked codes again. No codes.
I have had it sitting running for over 30 min and it has not shut off again.
Having two ICM's both the old one and the new one (which I changed out for good measure when I did the Opti) I think I could say it is not that as it does the same thing with both old and new.
If the fuel pump were going would it just shut off instantly when the pump quits? May sound dumb but I am new at injection. Im an old carb guy. Points / Condenser kind of stuff.
When this first started I suspected the pump.
It is going on 19 yrs old.
I dont mind spending the $$ but dont want to grocery shop.

hemivett

If disconnecting the battery worked, then you are OBD1, (as pcolt94 stated) and dont need to go to O'rielly's. They are a parts store here.

Now back to the problem. You could have any number of issues, from your oiling problem, ie. grounds. Your leak is coming from 1 of 3 places. Intake, head, or oil pressure sending unit, and all of them can leak onto those grounds. Also not sure what yr they started, but there is also a low oil pressure shut down switch, that could be getting soaked with oil, and ultimately killing the car. So try to find your leak, and clean your grounds.

The way it just dies for no reason really sounds electrical. check your battery cable too. Oil could be leaking onto the starter too, and causing a short.

Lastly, it could be one of the things you already replaced. Coils, and ignition mods are both effected by heat, and can do crazy stuff once there warmed up. Up here we have a salvage yard called pick n pull, where they have these items for cheap. Maybe you have something similar. May be a cheaper route for you, for testing. h

zilla24

Thanks hemivette
I went for a drive after it ran in my driveway for about 45 min. I went about 10-15 mi and it did not shut down.
I really hate intermittant problems.

The leak is tough to tell. It is wet at the back of the intake around where the spout comes out for the two sending units. I am going to have to really clean it all up real good and then run it to see where it is coming from. I have checked all the grounds I could eyeball and they all seem to be okay.

Low oil shut down.......hummm....dont know but I will investigate and see if they were on a 93.

What I really need is for my FSM's to get here as that think will help me identify where things are and Im sure help me troubleshoot.

I know back in the day they sold a dye set that worked with a black light for chasing down oil leaks. Dont know if they still make them.

Ill keep at it. I appreciate everyones input and think this is a great forum. I love the fact that there are people out there that really want to help!

Thanks to all and keep the ideas coming.......I love it!

hemivett

I hate intermitant prolems too, Right now I have SES light on in my Blazer for a trany problem, but it only throws a code long enough to turn on the light. I have literally had it turn on and pulled into a tranny shop within 500 feet, and there diag shows nothing. WTF?!

Sounds to me the leak is either the intake, or sending unit, or both. I believe that shut down switch is with the sending unit, (If you have one) and tells the computer its ok to start and run.

I need an FSM too, I have a chiltons, but when it comes to tech, its virtually worthless. Here's one for you. http://www.ebay.com/itm/1993-Chevrol...1256a6&vxp=mtr

Lol, I haven't seen the dye in years. I think you're dating yourself. I like to use SuperClean on my stuff. Really works well. I take it to the carwash without letting it warm up, (mines 2 blocks away) squirt the engine bay with cleaner, so it has time to soak in, and cover the ignition parts with plastic. Then I start the car, and start spraying. Your engine compartment will look like it just came from the showroom. Peace. h

pcolt94

Mod-9 Code H72 This is tied to the Radio? No, this is the EBTCM brake module - module 9.
You would be getting a SERVICE ASR light which is a serial data line malfunction. If you don’t have the FSM, I assume then you can't look this up and conclude you do not have this problem. Also you can't clear codes in module 9 by removing the battery cable (unlike 1 & 4). You have to use the onboard diagnostics using the 9.7 to erase the codes.


A lot of us have come from that time and still have those skills. Making the transition to computer control and FI over the last 35 years for me was not to hard as I have been in electronics since I have been walking and electrical engineering. Working on today's cars is more electrical than mechanical. It's really repairing electrical circuits which is the hat I wear mostly working on the new cars. A good basic understanding of electronics, knowing how to use a meter and reading the theory of operation in the FSM will give you a good incite and knowledge which are needed to understand "how things work".

The basics are the same, you need fuel and spark to run the engine. Delivery is a bit different but once you understand the theory of operation troubleshooting becomes a bit more straight forward.

theadmiral94

No shut-down is great, albeit suggest checking for codes anyway, as 'history' codes may assist in helping.

re oil shut-down, how steady is the analog oil pressure gauge on the dash? does it ever drop below the next to lowest mark (implying less than 20psi)? If not steady or dropping below 20psi, or leaking, it could be shutting down the fuel pump and causing the problem.

Some folks will advise the longer oil sender provides oil pressure gauge signal and a duplicate power feed to the fuel pump (in parallel to the ECM). This seems to me to be counter-intuitive and I wonder if the ECM provides power at startup, and then the 'oil pressure/fuel switch' sender takes over. If I am right, and that sender fails or intermittenly fails, it could cut-off the fuel pump, causing the engine to die. Unlike carb engines, fuel injectors require constant fuel pressure in the fuel rail to operate (40 psi +/-) and when that pressure drops below some point (20psi ?), nothing comes out of the injectors.

BTW, additional thought -- next time the car just shuts-off, try and get out quickly and smell the tail pipes for excess gas, if so, would suggest ignition issue, if not, suggests fuel issue.

zilla24

Thank you all.
I did check again for codes and only have the Mod-9 Code H72 which I obviously did not clear. I need to figure out how to clear that one.
The other codes
Mod-1 Code H41
Mod-4 Code H16
I did clear prior to the last shut down and it did not throw another code.

I kind of get how this electronic stuff works and have a working knowledge of a VOM. It is just a whole new way of thinking and the way some of the sensors and circuits are related is a bit illogical in my mind but who am I?

I will keep plugging away and continue to read and absorb and again I really love you guys and all your input. Keep it coming and Many Thanks to all!

Oh yea!
Merry Christmas to all!

James93LT1

http://tech.corvettecentral.com/2011...trouble-codes/

Sargevette

When it shuts down are you at idle? My 93 had the same oil leak. Turned out to be the intake gasket at the rear and front. I replaced the gaskets and all was good after that. The reason I ask about being at idle I also had a similar problem. Turned out to be the IAC motor pintle was dirty and binding the motor that drives it. Kept dying when I would go to idle at a stop light. I always suspect the opti which I replaced on mine too. Although I had codes telling me that. Could be the coil. Good luck on your findings.

zilla24

Thank you James!

Hey Sarge,
It generally shuts down at low RPM or at idle, but it did die once on acceleration at about 120 MPH "just kidding" at about 45MPH.
So far no more codes.

I am going to tackle the leak and get that out of the way. The two sending units are soaked so I am going to replace those as well. Then I will see what we have after that.

Thanks and Merry X-mas!

pcolt94

Great post with a lot of information not easly found (unless you have a FSM) including how to clear module 9 codes.
I will save this one.