Hey guys,
My father recently has bought himself an '89 supra 7mgte manual with about 110k original miles on the dash. The car was purchased from a younger guy out of VA who lost time or interest for the car and wanted to see it go to a good home. It was in great condition and well-maintained/documented. At the time of purchase the car's only upgrade was a Turboxs RFL bov vented to atmosphere and a turboback 3in exhaust. Apart from running decently rich from this VTA set-up, the car ran really well. But a few weeks after owning it, the car started to emit the dreaded blueish-smoke and began to run hotter. We both knew that these cars had the HG issues, so that was our first project. We started the tear down, carefully removing and labeling everything. We sent the head to get a complete port-and-polish, new seals and valves and check the deck surface for warping. We bought a Toyota OEM gasket and ARP studs and torqued to spec (~80 ft-lbs). While everything was apart we figured we would do a few mods: lex afm, 550s, FPR, Walbro 255, 57 trim ct-26, new cxracing intercooler kit, gauges to monitor afr and boost, revert back to oem intake/bpv and a complete gasket kit. We used the TSRM to carefully install everything properly to it's factory location, even saving all of the original EGR components. We had been searching the forum DIY's for any other process we completed.
SO, on to the reason for posting in Tech. section instead of new member section?
When we had everything back together, the car began stumbling and idling really poorly, and would hesitate under any load. Car began throwing Code 52 for knock sensor.
We replaced the knock sensor and wiring per TSRM and forum's help. Ohm'ed out the sensor and everything is back to spec. Car still runs poorly.
We searched for WEEKS, chasing our tails.
We checked for boost leaks, none
We replaced new one-step colder plugs since the ones removed had a lighter colored electrode indicating high-temps, and the AFM with a new unit.
I read on another forum that using high-impedance injectors on a low-impedance system could cause some of the symptoms of what we were experiencing, so we bought new low-impedance RC 550cc injectors, also checking the resistor to make sure it wasn't blown: it was fine.
Now that the new injectors are on, the car runs VERY lean, idling at ~17.5 and under any throttle going down to maybe ~14.5-15.0
Car still throws Code 52. FPR reads 35 psi to the rail w/out vacuum and ~26 psi with.
Using mechanics stethoscope all plugs and injectors clicking normally, even under added throttle
Unplugged AFM and car ran noticeably worse, plugged back in.
I reset the EFI fuse, no change, checked again for vac. leaks none. The 3 coil packs ohm correctly as well as all 6 plug wires.
When searching, I saw similar threads with similar AFR's on the 550s and the majority of the threads either had an easy-fix like a melted fuse or they just fizzled out with no answer or update.
Hopefully there's something we're missing or simply dorked up, but can you guys please help us, if there is anything you all could think of we would greatly appreciate it :1zhelp:
Also I know that I can/should just purchase an SAFC or a piggyback and try and tune it out, but I know that there's a bigger issue since tons of guys on here run the 550s and lex afm without issues like this, especially lean issues.
My father recently has bought himself an '89 supra 7mgte manual with about 110k original miles on the dash. The car was purchased from a younger guy out of VA who lost time or interest for the car and wanted to see it go to a good home. It was in great condition and well-maintained/documented. At the time of purchase the car's only upgrade was a Turboxs RFL bov vented to atmosphere and a turboback 3in exhaust. Apart from running decently rich from this VTA set-up, the car ran really well. But a few weeks after owning it, the car started to emit the dreaded blueish-smoke and began to run hotter. We both knew that these cars had the HG issues, so that was our first project. We started the tear down, carefully removing and labeling everything. We sent the head to get a complete port-and-polish, new seals and valves and check the deck surface for warping. We bought a Toyota OEM gasket and ARP studs and torqued to spec (~80 ft-lbs). While everything was apart we figured we would do a few mods: lex afm, 550s, FPR, Walbro 255, 57 trim ct-26, new cxracing intercooler kit, gauges to monitor afr and boost, revert back to oem intake/bpv and a complete gasket kit. We used the TSRM to carefully install everything properly to it's factory location, even saving all of the original EGR components. We had been searching the forum DIY's for any other process we completed.
SO, on to the reason for posting in Tech. section instead of new member section?
When we had everything back together, the car began stumbling and idling really poorly, and would hesitate under any load. Car began throwing Code 52 for knock sensor.
We replaced the knock sensor and wiring per TSRM and forum's help. Ohm'ed out the sensor and everything is back to spec. Car still runs poorly.
We searched for WEEKS, chasing our tails.
We checked for boost leaks, none
We replaced new one-step colder plugs since the ones removed had a lighter colored electrode indicating high-temps, and the AFM with a new unit.
I read on another forum that using high-impedance injectors on a low-impedance system could cause some of the symptoms of what we were experiencing, so we bought new low-impedance RC 550cc injectors, also checking the resistor to make sure it wasn't blown: it was fine.
Now that the new injectors are on, the car runs VERY lean, idling at ~17.5 and under any throttle going down to maybe ~14.5-15.0
Car still throws Code 52. FPR reads 35 psi to the rail w/out vacuum and ~26 psi with.
Using mechanics stethoscope all plugs and injectors clicking normally, even under added throttle
Unplugged AFM and car ran noticeably worse, plugged back in.
I reset the EFI fuse, no change, checked again for vac. leaks none. The 3 coil packs ohm correctly as well as all 6 plug wires.
When searching, I saw similar threads with similar AFR's on the 550s and the majority of the threads either had an easy-fix like a melted fuse or they just fizzled out with no answer or update.
Hopefully there's something we're missing or simply dorked up, but can you guys please help us, if there is anything you all could think of we would greatly appreciate it :1zhelp:
Also I know that I can/should just purchase an SAFC or a piggyback and try and tune it out, but I know that there's a bigger issue since tons of guys on here run the 550s and lex afm without issues like this, especially lean issues.
Last edited:
