Computer problems with 92 Vette

Ok guys, I'm not only new to the forum, but new to Corvettes. Have a 92 Vette (standard) with 120k miles, just bought it from what I thought was a reliable friend. Drove great, but the AC didn't work. Took it to my mechanic. After verifying compressor and system worked properly, he showed me that by removing the negative terminal (reset) the air would blow very cold for about 30 min. BUT, since then I have had nothing but problems. Random codes are being thrown (Security, ABS, ARS) but the vehicle ran fine.  THEN, I went to the grocery on a HOT day, drove fine all the way there, but upon getting off the interstate I noticed it was idling around 2200. I parked and went into the store, and when I got out, IT WOULD NOT START. Starter only, I won't speculate what the problem was. By disconnecting the neg terminal I could get it to turn over, but could only make it keep running by pulsing (not just stepping on) the throttle. Couldn't get it home. THe next day, I went to leave keys in it to have it towed - AND IT FIRED RIGHT UP and I was able to drive it home. I'm in Birmingham Alabama, so the only recommendation was to take it to a place called Rainoldi's. BUT, although he acted like it was SOOO important to get it there first thing (last) Monday am, it has now been there over a week, and he's not even sure if he's gonna get to it this week. When I told him that I needed something more as far as timeframe, he told me just to come pick it up!  WOW! Anyway, I either need some help or a place not too far away to take it to. Feel free to post, email me at madmaxrich@gmail.com. Please, I have driven this thing less than 1 day total, and I'm absolutely sick. Any and all ideas are welcomed.

- Max
Birmingham, AL  

i am hoping that the trick you learned was not to pull the cable off with the engine running....

i would start with checking the grounds.... with a digital volt meter...

got one.. this test takes about 2 minutes to ***

set digital volt meter to 20 volt scale...    start the engine.. turn on the headlights...


measure from the negative battery cable bolt...   to the engine block..    a normal reading will be 0.04 volts..

measure from the negative battery cable bolt  to a chassis ground where you see ground wires attached..
a good reading will be 0.02 volts..

measure from that ground point to the engine block...   again.. 0.02 volts..

when you start seeing multiple codes... the first place to check is the ground side of the system..

you might also want to with the engine off.. disconnect the battery cables..   pour hot water over the cable boots... get the cable bolt out.. then more hot water and work the boot over the ring terminal.. clean the hidden corrosion from the ring terminal.. clean the underside of the head of the bolt..

what codes can you get from the check engine light...    you can jump the a and b terminals then turn the key on... if you don't have a code reader or a scan tool....

each code has many pages of trouble shooting..

perhaps this will help...  write down you scanned data on the proper line with the engine cold.. then with it hot and running..





there is a small chance that you have bad injectors and or a bad computer...

but check the grounds first..    

you can also do the same test with the positive side...  

Ok, thanks SO much for this waynep7122. Some of this is a little foreign to me, but I have friends I can ask. Tell me this though - what do you mean by "the A and B terminals" I am familiar with the LT1, but not so much the electrical system. I have a 93 Z28.  

little black connector under the middle of your steering column...   this is where you plug an OBD1 scan tool into...   NOT OBD2 unless it has the proper cables for gm..  prior to 96..


autozone.com has free repair info on your car...  at the upper right corner .. join then log in.. select your camaro...     when logged in.. just above where you selected .. you will see a link to repair info.. then in the left frame.. click repair info again..

AutoZone.com's online repair guides are an essential accessory for do-it-yourself automotive repair. Each vehicle-specific guide includes detailed information and graphics to help you get your car or truck back on the road. Included in most guides: step-by-step instructions with detailed photographs and drawings, wiring diagrams, specification charts and repair tips.

Covers All U.S. And Canadian Models of the 1993-98 Camaro and Firebird.

Engine Electrical
Emission Controls     this is the section to look at
Brakes
Suspension & Steering
Chassis Electrical
General Information & Maintenance
Engine & Engine Mechanical
Body & Trim
Drive Train
Fuel System

The following procedures apply only to 1993-94 vehicles with the 12-pin diagnostic connector only. A scan tool, such as GM's Tech 1® must be used to retrieve diagnostic trouble codes from 1995-98 vehicles with the 16-pin diagnostic connector. When using a scan tool, make sure to carefully follow all instructions supplied by the manufacturer.

Listings of the trouble for the various engine control system covered in this repair guide are located in this section. Remember that a code only points to the faulty circuit NOT necessarily to a faulty component. Loose, damaged or corroded connections may contribute to a fault code on a circuit when the sensor or component is operating properly. Be sure that the components are faulty before replacing them, especially the expensive ones.

The Data Link Connector (DLC) may be located under the dash and sometimes covered with a plastic cover labeled DIAGNOSTIC CONNECTOR.

The diagnostic trouble codes can be read by grounding test terminal B . The terminal is most easily grounded by connecting it to terminal A (internal ECM ground). This is the terminal to the right of terminal B on the top row of the DLC connector.

Once the terminals have been connected, the ignition switch must be moved to the ON position with the engine not running.

The Service Engine Soon or Check Engine light should be flashing. If it isn't, turn the ignition OFF and remove the jumper wire. Turn the ignition ON and confirm that light is now on. If it is not, replace the bulb and try again. If the bulb still will not light, or if it does not flash with the test terminal grounded, the system should be diagnosed by an experienced driveability technician. If the light is OK, proceed as follows.

The code(s) stored in memory may be read through counting the flashes of the dashboard warning lamp. The dash warning lamp should begin to flash Code 12. The code will display as one flash, a pause and two flashes. Code 12 is not a fault code. It is used as a system acknowledgment or handshake code; its presence indicates that the ECM can communicate as requested. Code 12 is used to begin every diagnostic sequence. Some vehicles also use Code 12 after all diagnostic codes have been sent.

After Code 12 has been transmitted 3 times, the fault codes, if any, will each be transmitted 3 times. The codes are stored and transmitted in numeric order from lowest to highest.


The order of codes in the memory does not indicate the order of occurrence.

If there are no codes stored, but a driveability or emissions problem is evident, the system should be diagnosed by an experienced driveability technician.

If one or more codes are stored, record them. Refer to the applicable Diagnostic Code chart in this section.

Switch the ignition OFF when finished with code retrieval or scan tool readings.


After making repairs, clear the trouble codes and operate the vehicle to see if it will reset, indicating further problems.





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you will also want to bookmark this site.... it has some info also....

http://www.fastbird93.com/Diagnostics.htm

open every link and read each and every word...  spend a week or two doing it...   you won't understand at first.. but its amazing what you will remember when you get under the hood...


there is a LOT more into than is listed on the AZ or the fastbird site...  for that you may need a factory service manual...  or online info by subscription.. but most things can be fixed with the az site.. and the fast bird info..

feel free to ask questions...  

Thanks again!  What I meant is that I ALSO have a '93 Camaro and am familiar with the LT1, but not really the electrical system. The car that has the problem is the '92 Vette. Would all you said apply to the '92 Vette. Thanks again!

- Max Richard
Birmingham, AL  

Also, (and this will show my inexperience) what exactly does "grounding to the engine block mean?"  Can I just use anywhere physically on the engine, like, say, the intake manifold or somewhere metal, or is there a specific connection?  

usually the negative battery cable is attached to the engine block.....

the starter motor draws the most amperage..   it is bolted/grounded to the block...  so it makes sense to have the negative battery cable attached to the block...

you can do this voltage drop test anywhere on the engine...  block, heads, intake...  brackets..



this test is important.. as the alternator puts out the current to the battery through  its external frame .. where it's bolted to the brackets that are bolted to the cylinder head or blocks...   then down to the large negative cable... and then to the battery..




i have found a lot of cars with hard starting problems have a loose... corroded.. improperly crimped battery cable end at the block...

for those... i do the voltage drop test with the starter cranking..   if i get more than about 1/2 a volt i know i am in trouble...


volt meters measure the difference in voltage at the places being tested..

on the ground side..  there should be almost NO difference  in voltage when there is power being used on the positive side of the circuit..

since electrons flow from negative to positive.. if you have a bad ground..  you won't have enough electrons to do the job..

when the items are turn on...  

if the ground side is totally disconnected. it won't turn on...

if the ground side is loose..  it may try to turn on.. but won't have enough energy to complete the job so it will shut back off..

ever heard the starter rapidly clicking?? when it would not start..????

the voltage was up.. when the solenoid was activated.. the current rushed in and pulled the plunger in.. but the voltage dropped do to the restriction ... this let the spring push the plunger back...  as soon as the plunger fell back the contacts to the starter opened and the big draw quit.. so the voltage built back up again..  since the key was still in the cranking position.. the plunger pulled in again.. the voltage dropped at the starter load was applied..  this can happen several times a second and make the click click click click...

so clean the battery terminals first..  then check the grounds or do a voltage drop test...  the voltage drop test will point you right at the problem areas...

try it on a good running car.. practice...  its really easy..