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1992 lt-1

rfbert

Member
Joined
Oct 29, 2012
Messages
6
Location
Brandon, Florida, United State
Corvette
1992 LT-1 Black Rose
HELP I am having problems with my 92 LT-1 After driving my ac cuts off asr light comes on and speed o drops to zero.I have noticed others have had this same or very similar issues.No dtc codes are indicated in any modules I have a Tech one diagnostic computer.I have checked and cleaned all ground connections and terminals per the service manual.Also when this happens the idle goes up to 1200 and it runs rough.Cycling the key resets the problem but it comes right back.Any help or input would be greatly appreciated.THANKS ROBERT
 
Welcome onto the boards there...

Not too many problems cannot be tracked back to DTC's, but you say all's clear there...

So check for mis-routed spark plug wires. They HAVE to be in the wire looms, because the high - enegy wires can emit EMI, same as a nuke, if mis-routed. Usually tho', that will light up some false codes.

Vacuum leaks can go for a while, without tripping codes (should show up as out-of-spec operating parameters in your scanner tho'). Does it lope idle when warm?
 
Welcome onto the boards there...

Not too many problems cannot be tracked back to DTC's, but you say all's clear there...

So check for mis-routed spark plug wires. They HAVE to be in the wire looms, because the high - enegy wires can emit EMI, same as a nuke, if mis-routed. Usually tho', that will light up some false codes.

Vacuum leaks can go for a while, without tripping codes (should show up as out-of-spec operating parameters in your scanner tho'). Does it lope idle when warm?
Thanks for your input.The vehicle has 20k original miles and all wiring etc... is as original It idles rough but steady at twelve hundred rpms
 
Thanks for the input. The vehicle has 20k original miles and is in untouched original condition except for new battery and thermostat and all vital fluids.when it acts up it idles rough but steady at around twelve hundred.It acts like it wants to stall at idle when in gear(auto)when stopped at a light.All wires etc... are in good condition and in original positions.I have tried a replacement ECM with the same results.I have been a Chrysler level four technician for twenty three years so I know my way around cars fairly well but am not yet familiar with this vehicles systems.It has me stumped for the moment.Thanks again.
 
You might check your manual for a section called drivability and emissions. In my 93 manual it is section 6E3-b-13 for rough unstable or incorrect idle.
 
That section has lots of good info but im pretty sure the idle is the result of the other conditions happening first(speedo.ac,asr light)Thanks for your input.Nice looking Vette you have.
 
You mention doing the grounds but I wonder if you did the ground on the right front of the engine for the coil,tachometer. You may not be familiar with the fact that the coil requires a heat sink grease between it and the block. The reason I mention that is I just went through the tachometer not working and when I cleaned the ground and put new heat sink grease on the back of the coil it went to working again. Another thing I did was to put dielectric grease into all the pin holes on the connectors. That made a significant change in how my car ran. and finally i did the dielectric grease thing with the ECM connectors and that made even more improvement. These cars are particularly fussy about the condition of the connectors and grounds. I only mention these things because I am not sure if the cars you have worked on for 23 years were anything like this ignition system. Incidently the electrics came from Bosch and is very similiar to what BMW used.


It finally hit me what you are talking about is very similiar to what I went through with a bad TPS and it cost me a ECM I did not need. Take a good look at the TPS information in the manual
 
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HELP I am having problems with my 92 LT-1 After driving my ac cuts off asr light comes on and speed o drops to zero.I have noticed others have had this same or very similar issues.No dtc codes are indicated in any modules I have a Tech one diagnostic computer.I have checked and cleaned all ground connections and terminals per the service manual.Also when this happens the idle goes up to 1200 and it runs rough.Cycling the key resets the problem but it comes right back.Any help or input would be greatly appreciated.THANKS ROBERT
I would see if your not dropping the vehicle speed sensor input. Loss of this could cause everything you are describing. Is it the Service ASR light?
 
Thanks for the input. The vehicle has 20k original miles and is in untouched original condition except for new battery and thermostat and all vital fluids.when it acts up it idles rough but steady at around twelve hundred.It acts like it wants to stall at idle when in gear(auto)when stopped at a light.All wires etc... are in good condition and in original positions.I have tried a replacement ECM with the same results.I have been a Chrysler level four technician for twenty three years so I know my way around cars fairly well but am not yet familiar with this vehicles systems.It has me stumped for the moment.Thanks again.

They're all the same on the inside. The exceptions to normal operations will get you EVERY time however.

That said, sometimes simple stuff gets the best of genius. Maybe start at page 1 of that section mentioned...;)
 
Thanks again.I noticed that according to the service information the tps signal travels through a filter module before sending the signal information to the brake system module.I will check this system out and check the ground at the ignition coil and keep you all posted.Thanks again.where does the vehicle speed get its displayed speed from,Transmission,Wheel speed sensors or the rear differential ?
 
Thanks for your input.The vehicle has 20k original miles and all wiring etc... is as original It idles rough but steady at twelve hundred rpms

This part of your statement bothers me...

Is 'HIGH IDLE' addressed in the 'Driveability and Emissions' section???
 
That section does talk about unstable idle. As I mentioned earlier I had a TPS that caused similiar symptoms. That is I had a very high idle and stalling when put in gear. And no with my car it did not code.
 

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