1JZ issue, helping a friend

[RacerXJ220]

I have a friend who just swapped in a stock twinned 1JZ into his 240, and he's having problem with it running.

It starts up on the first crank when cold, and idles fine.

During cold running the car seems to work great. After it warms up, it's difficult to start and there is a huge drop off of power.

Does anyone know what would cause this? Coolant temp sensor?

We just swapped out the head gasket, it was running hot and kept doing so. Now it doesn't overheat. It had the same symptoms before we swapped HG's. We are going to do a compression test, and I'll update this thread once we know those numbers.

It doesn't overheat anymore, and it doesn't burn any oil at idle or take off.

Thank you for any suggestions you may have.

 

[suprahero]

It could be the sensor Jeff. Do the AFR's stay good during the warmer runs or does it get richer/ leaner?

 

[935motorsports]

Try it with the EFI sensor unplugged.

It will be hard to start cold, but should work acceptable when it's warm.

I ran without the EFI sensor for a month or so until I found the problem.

If the problem still exists, then you know it's not the EFI sensor.

 

[suprahero]

Good suggestion Robert.

 

[RacerXJ220]

Robert, I am actually not familar with the EFI sensor. Which one is this?

His fuel pump is wired to the battery on a fuse + Bosch relay.

Jay, he doesn't have an AFR yet, he's stock and beating 12.8 second cars with a stock auto. It's crazy how much 1000 pounds less makes BPU.

 

[935motorsports]

On the water neck green 2 wire sensor.

Running stock ecu? Are there any piggybacks?

 

[RacerXJ220]

No piggy backs, just gutted from stock weight of 2700 pounds, no front or rear bumper supports, battery relocated, lightweight wheels, and just under fuel cut thresh hold, intake and open down pipe with large FMIC. I guess that's not stock, but I don't consider it really upgraded on factory electronics and injectors. Should be around 2500 pounds right now with him in it. I might be off on that estimate, but he took a lot out of it.

No heat, no AC components.

We'll disconnect that one and report back. I appreciate the help!!!!

 

[RacerXJ220]

If it were the ECU, could that hurt the motor? We're trying to figure out how he got a BHG on a 1J.

It's a Soarer ECU BTW. Not sure if those go bad like the Supra 1J's do. I have an extra, but it's for an manual transmission, not an auto.

If we put the manual ecu on the car, I'm not sure if it would work.

I'll open the ECU tonight also if the EFI trick doesn't help. Thank you Robert.

 

[suprahero]

Jeff, I ran an auto ecu on my manual for over a year with no problems.......but I'm not sure about a manual on an automatic car. Does the ECU tell it when to shift or does it have it's own little computer box for that?

 

[RacerXJ220]

I'm not sure about that Jay. I thought it was all controlled by the ECU but I could be wrong.

 

[JASONA70]

check out the ecu capacitor, open up the ECU and check out the cylinder shaped cap. If you find any leaking ooze or burnt smell then you need to change them out.