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Hey all, I need some help.
I have an 84’ Supra that was my first project car. I’m unf*cking everything I f*cked when I didn’t know anything about cars. So here’s the specs and the problem:

Originally automatic 84’ Celica Supra P-type with resealed 85’ Cressida 5MGE, new wiring harness, corresponding ecu. Mk3 Supra W58 manual transmission. Good compression, spark on all 6, fuel and air are good, timing is good, fuel pump/filter is good and injectors have a new seal and filter kit on them. No leaks.

The car is running-ish. It’ll hold a steady idle around 1200 but takes a sec to get there. It’ll jump every 10 secs or so to 4k rpms then settle back down. If I give it any gas, it’ll jump to 4k. I thought it was the TPS but I changed it as well as got the corresponding ECU and no change. I’m at a loss. Please help!
 

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1983 Red Mk2 M/T 7MGTE Swap, Bone stock M/T Black Mk2 1984, 1989 Red Mk3 A/T Turbo
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Hey all, I need some help.
I have an 84’ Supra that was my first project car. I’m unf*cking everything I f*cked when I didn’t know anything about cars. So here’s the specs and the problem:

Originally automatic 84’ Celica Supra P-type with resealed 85’ Cressida 5MGE, new wiring harness, corresponding ecu. Mk3 Supra W58 manual transmission. Good compression, spark on all 6, fuel and air are good, timing is good, fuel pump/filter is good and injectors have a new seal and filter kit on them. No leaks.

The car is running-ish. It’ll hold a steady idle around 1200 but takes a sec to get there. It’ll jump every 10 secs or so to 4k rpms then settle back down. If I give it any gas, it’ll jump to 4k. I thought it was the TPS but I changed it as well as got the corresponding ECU and no change. I’m at a loss. Please help!
sounds like timing
 

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Hey all, I need some help.
I have an 84’ Supra that was my first project car. I’m unf*cking everything I f*cked when I didn’t know anything about cars. So here’s the specs and the problem:

Originally automatic 84’ Celica Supra P-type with resealed 85’ Cressida 5MGE, new wiring harness, corresponding ecu. Mk3 Supra W58 manual transmission. Good compression, spark on all 6, fuel and air are good, timing is good, fuel pump/filter is good and injectors have a new seal and filter kit on them. No leaks.

The car is running-ish. It’ll hold a steady idle around 1200 but takes a sec to get there. It’ll jump every 10 secs or so to 4k rpms then settle back down. If I give it any gas, it’ll jump to 4k. I thought it was the TPS but I changed it as well as got the corresponding ECU and no change. I’m at a loss. Please help!
Wow, 4,000RPM! Are you sure the cruise control servo isn't doing that. I am very surprised the engine will hit 4,000RPM with the throttle body closed, but I've been wrong before and most likely will be again before the day is over. Also, I am fairly sure the ECU are A/T and M/T specific. Auto trans have a speed sensor that feeds info to the ECU and ECT that I am fairly sure is absent on the manual transmission. A lot of talk and no information I know, but maybe this will get the ball rolling.
JR
 

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Discussion Starter · #5 ·
Wow, 4,000RPM! Are you sure the cruise control servo isn't doing that. I am very surprised the engine will hit 4,000RPM with the throttle body closed, but I've been wrong before and most likely will be again before the day is over. Also, I am fairly sure the ECU are A/T and M/T specific. Auto trans have a speed sensor that feeds info to the ECU and ECT that I am fairly sure is absent on the manual transmission. A lot of talk and no information I know, but maybe this will get the ball rolling.
JR
Well I took the cruise control module out a while back it’s possible, but on a Facebook post about it, someone mentioned the cold start valve. I messed around with the injectors and that valve but no change. I’m not sure what it’s problem is. I appreciate it!
 

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I'd suggest you have a massive vacuum leak somewhere post throttle body.
 
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When you're getting these cyclical surges in RPM, it's usually a vac leak. This sounds like a rather large one, surprised you can't hear air rushing in from somewhere

EGR tubes all hooked up?

Check brake booster hose. One time I whacked the brake booster when dropping a new engine in, caused a big leak.
 
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