Help! Supra doesn't run right

[Abe's 1987]

Here is my situation. My 1987 turbo idles erratically between 1000 to 2000 rpm. When i try to rev up its like it hits fuel cut at 3000 rpm and won't rev past 3000 rpm. So far I've tested tps, iacv, vacuum system, timing, and afm. All seems to be within specs. Ive checked to make sure my spark plug wires were on right and torqued the plugs to spec. Compression of all cylinders were within 118 to 122 psi dry test. Oil pressure is within specs. I changed fuel filter. I checked for boost leaks and fixed a few leaks. If I pinch the hose going from the iacv to the intake the idle stops fluctuating but still won't rev past 3000 rpm. I had to fix a couple vacuum mishaps. I even turned the throttle idle screw clockwise and counterclockwise but didn't help. But still having the problem. Tsrm doesn't seem to have any troubleshooting for my situation. Any pointers, tips, or similar problem repairs would be great help. Ive been using the tsrm and just can't pin point my problem.

 

[suprahero]

Have you tried another ecu just to eliminate that as a problem?

 

[plaaya69]

Are your grounds good coming from the engine wiring harness going under the intake manifold and also the main grounds that go on the block and cylinder head?

 

[suprarx7nut]

You mention a lot of checks, but have you pulled codes?

 

[Abe's 1987]

No have not tried another ECU. Might have to see if I could get a loaner.

 

[Abe's 1987]

Haven't check grounds yet. Will do it tonight.

 

[Abe's 1987]

Yes I checked for codes and there are no codes.

 

[Abe's 1987]

Ok checked grounds all good. Had to order a cold start ignition timing switch as mine was broken. Installed it and it didn't make a difference. Only last thing i can think of is ecu. If anyone has one at a good price let me know. It is a 89+ turbo 5 speed manual, I'm guessing the year as the engine had been changed. I will get the part number by tomorrow night off the ecu.

 

[Abe's 1987]

So far tsrm has been a great guide compared to most repair manuals I've used in the past. To bad it can't diagnose my car for me. Lol. I'm pretty sure that is called a mechanic. But yeah still looking for a ecu. I'm pretty sure that is my problem. Or even I could borrow one just to see if that's the problem from anyone I'd appreciate it.

 

[3p141592654]

3000 rpm fuel cut usually means the AFM signal is bad and its running in limp mode. You sure there is no code set?

 

[Abe's 1987]

I check the afm as the tsrm says to with a multi meter and I got the ohms reading within specs. I also opened the ecu and everything looks to be good. When i get the supra started no check engine light. I jumped E1 with TE1 and the check engine light just blinks continuously none stop so i guessed that means no codes. At this point im stumped. I've have come to a point where I guess I just have to keep swapping parts out to find the issue. Problem is that is going to cost a pretty pennie.

 

[Abe's 1987]

Only thing I haven't tested was fuel pressure but I don't think it would cause these issues would it? But yeah if anyone has some extra parts I could use to eliminate possible suspects aka (tps, iacv, afm, ecu, ect.....) to loan I'd be willing to pay shipping and ship it back as soon as I test it I'd appreciate it.

 

[plaaya69]

When my AFM got destroyed along time ago (Because I used crc mass air flow sensor cleaner when it first came out and it had no warnings on the label like it does now "not to use in Toyota Supra Turbo") it would not go past 3k rpms. Usually also when the ISCV goes bad it will make the Supra idle at 3k rpms. I made a quick video of my turbo Supra running with the AFM unplugged and the symptoms it shows. Is this how yours is running?

https://youtu.be/MQHoO1Pz3MI

 

[Abe's 1987]

Here is two vids of the supra running. Hopefully this helps.
https://m.youtube.com/watch?v=2Zf-RpcMDN8
https://m.youtube.com/watch?v=itpl96_7WAg

 

[Abe's 1987]

The things I do notice now since fixing a few of the problems the idle does now fluctuates between 1500 and 2000 rpms and now it wont rev past 2500 rpms. The starter was tested good as its a new starter but as you can hear in the videos it has problems starting, not sure why it does that.

 

[3p141592654]

Has it ever run properly with the setup you have there? One thing I notice is the lack of a fan shroud right next to the AFM with an exposed filter which could be causing turbulence at the AFM. Try shielding the air filter from the fan with a piece of cardboard or sheet metal. Also make sure the honeycomb is still on the front of the AFM.

 

[3p141592654]

The other thing I would check is the IDL signal, since it seemed to smooth out when you unplugged the TPS. Could be the trailing throttle fuel cut being acitvated because your IDL signal is not set correctly or the TPS is broken.

This is the symptom of a maladjusted TPS.
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=125

and this is how you check the IDL signal.
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=101

 

[Abe's 1987]

So it has been running like this since i bought the supra. Ive had it for coming up to two months. I will check all these in the morning.

 

[Abe's 1987]

Ok so the honeycomb is on. I also decided to double check the ohms reading of the tps, iacv, and afm. So now the afm has no readings even though prior it was reading within specs. And I think based on my readings I has to also adjust the tps or it is bad as well . Iacv is still reading good.

 

[Piratetip]

Try a new or known working AFM.