7MGTE will not idle for more than 30 seconds!

SteelMaverick · 03-27-2021, 07:56 PM

Fresh rebuild. Lexus AFM, 550 injectors, Wahlbro 255 fuel pump with 12v mod and Aeromotive AFPR. . Ok, heres the whole story from when I got the motor in the car and hooked up to everything. Got it started and it idled perfectly. Then after a couple of run ups and shutting it off to check for leaks, loose hoses etc.. then realized although it idled perfectly it wouldn't rev past 2800 rpm. adjusted fuel pump to 40 psi with vacuum line off and then noticed we forgot to plug in the AFM. Got it started and it revved past 2800 like normal but then developed the idle issue. Checked the voltage at the fuel pump (12v mod) and getting 13.85 volts so it seem normal and staying on. Took out the number 1 spark plug and it was fouled. Replaced the plugs. Lots of black soot so assume its getting too much fuel. Checked the Idle control valve and its good. I checked the cam gears and crank set to 0. lines up perfectly. No matter where I set the CPS for timing it doesn't help. Not sure where to go next..... Oh, also replaced the cheap AFPR because it was leaking and thought maybe it was bad but didn't help and removed the PS belt because it sounds like its going bad and thought it might be starting to freeze up and binding the motor but that didn't help either. And swapped the ECU but nothing.

Obviously I'm missing something.. Why did it idle perfectly before I adjusted the fuel pressure and connected the AFM? I tried readjusting the fuel and unplugging the AFM but it dies even faster then. Any suggestions? Thanks.

Oh and also there is a small oil leak under the turbo somewhere (I think where the oil return line is connected to the block) and the turbo gauge isn't working.

yale · 06-02-2021, 01:33 PM

Check the vacuum line connections. There is a wiring diagram in the manual (link on this site) to make sure those routed correctly. I had an idle issue at one time because of a missed vacuum connection.
Can you keep it running with throttle input? If so get it warmed up and see if the idle comes back to you. If so you have an issue somewhere within the cold start circuit.
I had the same issue with horrible idle and throttle response that turned out to be a leak in the intake plenum gaskets (lower plenum to block).
You can also try spraying some carb cleaner around the injectors and intakes to see if that smooths the idle. If so you got a leak.

03-27-2021, 07:56 PM	#1
SteelMaverick Stock Join Date: Mar 2021 Location: Idaho, USA Posts: 1	7MGTE will not idle for more than 30 seconds! Fresh rebuild. Lexus AFM, 550 injectors, Wahlbro 255 fuel pump with 12v mod and Aeromotive AFPR. . Ok, heres the whole story from when I got the motor in the car and hooked up to everything. Got it started and it idled perfectly. Then after a couple of run ups and shutting it off to check for leaks, loose hoses etc.. then realized although it idled perfectly it wouldn't rev past 2800 rpm. adjusted fuel pump to 40 psi with vacuum line off and then noticed we forgot to plug in the AFM. Got it started and it revved past 2800 like normal but then developed the idle issue. Checked the voltage at the fuel pump (12v mod) and getting 13.85 volts so it seem normal and staying on. Took out the number 1 spark plug and it was fouled. Replaced the plugs. Lots of black soot so assume its getting too much fuel. Checked the Idle control valve and its good. I checked the cam gears and crank set to 0. lines up perfectly. No matter where I set the CPS for timing it doesn't help. Not sure where to go next..... Oh, also replaced the cheap AFPR because it was leaking and thought maybe it was bad but didn't help and removed the PS belt because it sounds like its going bad and thought it might be starting to freeze up and binding the motor but that didn't help either. And swapped the ECU but nothing. Obviously I'm missing something.. Why did it idle perfectly before I adjusted the fuel pressure and connected the AFM? I tried readjusting the fuel and unplugging the AFM but it dies even faster then. Any suggestions? Thanks. Oh and also there is a small oil leak under the turbo somewhere (I think where the oil return line is connected to the block) and the turbo gauge isn't working. __________________ 1988 Supra Turbo Targa.

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06-02-2021, 01:33 PM	#2
yale Intake Join Date: Oct 2015 Location: CT Posts: 38	Check the vacuum line connections. There is a wiring diagram in the manual (link on this site) to make sure those routed correctly. I had an idle issue at one time because of a missed vacuum connection. Can you keep it running with throttle input? If so get it warmed up and see if the idle comes back to you. If so you have an issue somewhere within the cold start circuit. I had the same issue with horrible idle and throttle response that turned out to be a leak in the intake plenum gaskets (lower plenum to block). You can also try spraying some carb cleaner around the injectors and intakes to see if that smooths the idle. If so you got a leak.