Here's the scenario.
Vehicle: 1992 N/A Supra
Engine/Harness/ECU: 1991 7MGTE
Turbo: Modified CT-26
Air Flow Metering Device: MAFT w/ 3.5" GM MAF
Fuel: Aeromotive AFPR, Walbro 255lph, Precision 550cc injectors, Driftmotion Fuel Damper Bypass and AFPR kits installed.
Ignition: NGK Iridium IX BKR8EIX Spark Plugs (did not gap, as they are recommended not to be) Issue is present with both Stock Ignition coils and wires, as well as 2JZ VVTi Coils and wires.
Knock sensors: 1 brand new, and one used. Both 92+ style. The used one came from the original 86k mile 92 7MGE engine, which ran perfect with no codes.
Codes Present:
Code 52, but only after raising rpm above 2.5k rpm, and under slight load.
Symptom:
Engine intermittently misfires at idle and through the RPM range. Above ~3.5k missfire increases and Code 52 is thrown. Missing cylinder has yet to be identified. At times it idles and revs perfectly smooth with no miss. sometimes it seems to idle fine, but breaks up with increased throttle. Sometimes it has a constant miss at idle and all rpm. Also, when I press the throttle closed all the way, using the throttle linkage in the engine bay (all the way against the bump stop), the engine stumbles and sometimes dies. Not sure if that is normal.
Diagnostics Performed:
Pulled all plugs and all are black with carbon like each cylinder is running rich. I assume this is because the O2 sensor is reading lean from the lack of combustion in the missing cylinder(s), causing the ECU to enrichen the fuel mixture. No significant variation in color between them.
The misfire remains unchanged whether the vehicle is started and run with the MAF connected or disconnected. The MAF and MAFT setup came from a friend with a good running vehicle. I have not 'tested' the MAFT, although based upon my observations it seems to be operating normally (Green light dim at idle and brightens with throttle. Red flashes once on startup). The GM 3.5" MAF tested within spec.
The CPS wiring is all good. I replaced the harness side connector and checked the wires/connector on the CPS and they are good as well.
Fuel pressure was set to 43psi base with T1 and E1 jumped. That being said, fuel pressure drops to ~32 psi when the throttle is depressed under no load (free revving) and vacuum applied. I'm unsure of whether or not that is within spec. I thought it may have been bad gas, as the car sat with less than 1/8th of a tank for five months while I performed the GTE swap. To correct this, I filled it completely with fresh 93 and the problem has not changed; though the burned fuel does smell better.
The issue is the same with both the stock coil pack and wires, as well as with the 2JZ VVTi COP mod (I've tested both ways). All coils and wires were tested and are within spec. With key on, each ignition coil has 12V at pin 1 of each connector (within spec). Wires and Coils all ohmed and within spec.
I have not yet tested the TPS, although I did notice that it has a blue part number sticker on it; which, to my knowledge, indicates it is for a pre-1990 throttle body whereas a later model throttle body would have a red part number sticker. Now, I purchased the complete engine, harness, and ECU setup locally from a car that I watched start and run with no idle or drivability issues. I'm not sure if he ever replaced the whole throttle body with an earlier unit, allowing for use of the older style sensor; or if the wrong sensor is currently installed on a late model throttle body. How can I identify the year of the throttle body and/or what sensor is supposed to be used? Or, is it not an issue of the year of the throttle body, but of the ECU/wiring harness? Either way, I plan to test the TPS via the TSRM. I will reply with the results.
I rewired the knock sensors using RG-6 coax cable. I tested for continuity between the shielding and ECU pin for each knock sensor circuit and there is no continuity (good). There is also no continuity between the knock sensor circuits. I will have to pull the alternator and ohms test the complete circuits from the sensors to the ECU pinouts to verify their integrity. I will also test the sensors themselves. However, while these items may be causing the code 52, I believe they are unrelated to the misfire.
I feel like there's an issue with the ignition system, possibly bad wiring in the harness somewhere causing the miss to occur intermittently. I've heard of the 'igniter ground mod,' which I have not yet done and need to read into. Looking for any guidance as to what system/subsystems I may have overlooked and what a good approach to tackling this issue may be. I'll answer all questions as concisely as possible. Thanks in advance for your help.
-Chris
RESOLUTION CLIFFS
Thanks again to everyone who has helped to diagnose these issues.
CLIFFS:
Misfire due to loose injector connector.
Code 52 due to disconnected rear Knock Sensor connector.
When troubleshooting an issue with a vehicle, always practice the KISS method! Keep It Simple, Stupid!
Information regarding break-up @ 3500 RPM can be found here:
http://www.supramania.com/forums/sh...egardless-of-Load-Boost&p=1827163#post1827163
Vehicle: 1992 N/A Supra
Engine/Harness/ECU: 1991 7MGTE
Turbo: Modified CT-26
Air Flow Metering Device: MAFT w/ 3.5" GM MAF
Fuel: Aeromotive AFPR, Walbro 255lph, Precision 550cc injectors, Driftmotion Fuel Damper Bypass and AFPR kits installed.
Ignition: NGK Iridium IX BKR8EIX Spark Plugs (did not gap, as they are recommended not to be) Issue is present with both Stock Ignition coils and wires, as well as 2JZ VVTi Coils and wires.
Knock sensors: 1 brand new, and one used. Both 92+ style. The used one came from the original 86k mile 92 7MGE engine, which ran perfect with no codes.
Codes Present:
Code 52, but only after raising rpm above 2.5k rpm, and under slight load.
Symptom:
Engine intermittently misfires at idle and through the RPM range. Above ~3.5k missfire increases and Code 52 is thrown. Missing cylinder has yet to be identified. At times it idles and revs perfectly smooth with no miss. sometimes it seems to idle fine, but breaks up with increased throttle. Sometimes it has a constant miss at idle and all rpm. Also, when I press the throttle closed all the way, using the throttle linkage in the engine bay (all the way against the bump stop), the engine stumbles and sometimes dies. Not sure if that is normal.
Diagnostics Performed:
Pulled all plugs and all are black with carbon like each cylinder is running rich. I assume this is because the O2 sensor is reading lean from the lack of combustion in the missing cylinder(s), causing the ECU to enrichen the fuel mixture. No significant variation in color between them.
The misfire remains unchanged whether the vehicle is started and run with the MAF connected or disconnected. The MAF and MAFT setup came from a friend with a good running vehicle. I have not 'tested' the MAFT, although based upon my observations it seems to be operating normally (Green light dim at idle and brightens with throttle. Red flashes once on startup). The GM 3.5" MAF tested within spec.
The CPS wiring is all good. I replaced the harness side connector and checked the wires/connector on the CPS and they are good as well.
Fuel pressure was set to 43psi base with T1 and E1 jumped. That being said, fuel pressure drops to ~32 psi when the throttle is depressed under no load (free revving) and vacuum applied. I'm unsure of whether or not that is within spec. I thought it may have been bad gas, as the car sat with less than 1/8th of a tank for five months while I performed the GTE swap. To correct this, I filled it completely with fresh 93 and the problem has not changed; though the burned fuel does smell better.
The issue is the same with both the stock coil pack and wires, as well as with the 2JZ VVTi COP mod (I've tested both ways). All coils and wires were tested and are within spec. With key on, each ignition coil has 12V at pin 1 of each connector (within spec). Wires and Coils all ohmed and within spec.
I have not yet tested the TPS, although I did notice that it has a blue part number sticker on it; which, to my knowledge, indicates it is for a pre-1990 throttle body whereas a later model throttle body would have a red part number sticker. Now, I purchased the complete engine, harness, and ECU setup locally from a car that I watched start and run with no idle or drivability issues. I'm not sure if he ever replaced the whole throttle body with an earlier unit, allowing for use of the older style sensor; or if the wrong sensor is currently installed on a late model throttle body. How can I identify the year of the throttle body and/or what sensor is supposed to be used? Or, is it not an issue of the year of the throttle body, but of the ECU/wiring harness? Either way, I plan to test the TPS via the TSRM. I will reply with the results.
I rewired the knock sensors using RG-6 coax cable. I tested for continuity between the shielding and ECU pin for each knock sensor circuit and there is no continuity (good). There is also no continuity between the knock sensor circuits. I will have to pull the alternator and ohms test the complete circuits from the sensors to the ECU pinouts to verify their integrity. I will also test the sensors themselves. However, while these items may be causing the code 52, I believe they are unrelated to the misfire.
I feel like there's an issue with the ignition system, possibly bad wiring in the harness somewhere causing the miss to occur intermittently. I've heard of the 'igniter ground mod,' which I have not yet done and need to read into. Looking for any guidance as to what system/subsystems I may have overlooked and what a good approach to tackling this issue may be. I'll answer all questions as concisely as possible. Thanks in advance for your help.
-Chris
RESOLUTION CLIFFS
Thanks again to everyone who has helped to diagnose these issues.
CLIFFS:
Misfire due to loose injector connector.
Code 52 due to disconnected rear Knock Sensor connector.
When troubleshooting an issue with a vehicle, always practice the KISS method! Keep It Simple, Stupid!
Information regarding break-up @ 3500 RPM can be found here:
http://www.supramania.com/forums/sh...egardless-of-Load-Boost&p=1827163#post1827163
Last edited:
