93 rough idle
Thread Starter
3rd Gear
Joined: Jul 2014
Posts: 3
Likes: 0
93 rough idle
have a 93 vette with injectors 1,3,5,7 not firing. It "fixed" itself one afternoon as I let it idle 45 minutes to keep battery charged. You could feel all 8 injectors pulsing but 2 days later same problem-1,3,5,7 not firing. Injector fuses good, all 8 plugs firing-optispark good and had computer rebuilt recently
Is there a computer relearn procedure for this model?
Is there a computer relearn procedure for this model?
Safety Car
Joined: Jun 2003
Posts: 4,250
Likes: 656
From: San Diego Ca
Our 93s have a batch fire system so each bank of injectors are fired at the same time by the ECU.
Sounds like you have a problem with the system.
You say you can "feel" all injectors pulsing but have you put an injector tester on each injector. They are very inexpensive and you can test each injector separately.
How about the old drop of water on each exhaust manifold to see if they are hot (firing) or even neater an infrared thermometer to make certain which cylinders have combustion and which don't.
Sounds like you have a problem with the system.
You say you can "feel" all injectors pulsing but have you put an injector tester on each injector. They are very inexpensive and you can test each injector separately.
How about the old drop of water on each exhaust manifold to see if they are hot (firing) or even neater an infrared thermometer to make certain which cylinders have combustion and which don't.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I would suspect a wiring problem. All 8 injectors are connected together and they all fire at the same time, so if some are not firing then they are not connected for some reason. Another possibility is that one bank is not getting 12 volts from the fuse panel (bad connection or bad fuse).
Thread Starter
3rd Gear
Joined: Jul 2014
Posts: 3
Likes: 0
Our 93s have a batch fire system so each bank of injectors are fired at the same time by the ECU.
Sounds like you have a problem with the system.
You say you can "feel" all injectors pulsing but have you put an injector tester on each injector. They are very inexpensive and you can test each injector separately.
How about the old drop of water on each exhaust manifold to see if they are hot (firing) or even neater an infrared thermometer to make certain which cylinders have combustion and which don't.
Sounds like you have a problem with the system.
You say you can "feel" all injectors pulsing but have you put an injector tester on each injector. They are very inexpensive and you can test each injector separately.
How about the old drop of water on each exhaust manifold to see if they are hot (firing) or even neater an infrared thermometer to make certain which cylinders have combustion and which don't.
Safety Car
Joined: Jun 2003
Posts: 4,250
Likes: 656
From: San Diego Ca
You say you had the computer "rebuilt" recently. As far as I know you don't "rebuild" the 93 CPU. It does have a removable eprom not an installed eeprom like the later cars.
Do you have a spare or can you borrow a spare 93 CPU? It only takes a 10 mm socket and 2 minutes to pull out and change out. You would need to pull your chip and put it in the new and that would tell you if it is a problem in the CPU wiring with one exception, and that is if the short/bad connection is in the pin in portion going to the mass of wires that are collected in the wire bundles that slide onto the ECU.
I do not have my helms here as my 93 is at a remote garage, but you should find the pin in that controls each bank of injectors and make sure that connection is inserted correctly.
As Harris says, it also seems like the time to carefully follow the wiring diagram and find out if you have a short.
BTW, the 93 ECU is the same part in the Y Body as in the F Body. The chip is different but the ECU itself is identical. So if you can find an ECU for a Camaro/Firebird from 93 you are good to go. Just change the physical CalPack Chip and put the ECU into your car and see what happens.
Where are you located?
92-93 Corvette, 93 Camaro/Firebird ECU
Do you have a spare or can you borrow a spare 93 CPU? It only takes a 10 mm socket and 2 minutes to pull out and change out. You would need to pull your chip and put it in the new and that would tell you if it is a problem in the CPU wiring with one exception, and that is if the short/bad connection is in the pin in portion going to the mass of wires that are collected in the wire bundles that slide onto the ECU.
I do not have my helms here as my 93 is at a remote garage, but you should find the pin in that controls each bank of injectors and make sure that connection is inserted correctly.
As Harris says, it also seems like the time to carefully follow the wiring diagram and find out if you have a short.
BTW, the 93 ECU is the same part in the Y Body as in the F Body. The chip is different but the ECU itself is identical. So if you can find an ECU for a Camaro/Firebird from 93 you are good to go. Just change the physical CalPack Chip and put the ECU into your car and see what happens.
Where are you located?
92-93 Corvette, 93 Camaro/Firebird ECU
Last edited by pkincy; Aug 20, 2014 at 12:29 PM.
Thread Starter
3rd Gear
Joined: Jul 2014
Posts: 3
Likes: 0
You say you had the computer "rebuilt" recently. As far as I know you don't "rebuild" the 93 CPU. It does have a removable eprom not an installed eeprom like the later cars.
Do you have a spare or can you borrow a spare 93 CPU? It only takes a 10 mm socket and 2 minutes to pull out and change out. You would need to pull your chip and put it in the new and that would tell you if it is a problem in the CPU wiring with one exception, and that is if the short/bad connection is in the pin in portion going to the mass of wires that are collected in the wire bundles that slide onto the ECU.
I do not have my helms here as my 93 is at a remote garage, but you should find the pin in that controls each bank of injectors and make sure that connection is inserted correctly.
As Harris says, it also seems like the time to carefully follow the wiring diagram and find out if you have a short.
BTW, the 93 ECU is the same part in the Y Body as in the F Body. The chip is different but the ECU itself is identical. So if you can find an ECU for a Camaro/Firebird from 93 you are good to go. Just change the physical CalPack Chip and put the ECU into your car and see what happens.
Where are you located?
92-93 Corvette, 93 Camaro/Firebird ECU
Do you have a spare or can you borrow a spare 93 CPU? It only takes a 10 mm socket and 2 minutes to pull out and change out. You would need to pull your chip and put it in the new and that would tell you if it is a problem in the CPU wiring with one exception, and that is if the short/bad connection is in the pin in portion going to the mass of wires that are collected in the wire bundles that slide onto the ECU.
I do not have my helms here as my 93 is at a remote garage, but you should find the pin in that controls each bank of injectors and make sure that connection is inserted correctly.
As Harris says, it also seems like the time to carefully follow the wiring diagram and find out if you have a short.
BTW, the 93 ECU is the same part in the Y Body as in the F Body. The chip is different but the ECU itself is identical. So if you can find an ECU for a Camaro/Firebird from 93 you are good to go. Just change the physical CalPack Chip and put the ECU into your car and see what happens.
Where are you located?
92-93 Corvette, 93 Camaro/Firebird ECU
