Dies once hot, will not restart until cold

[Raven97990]

1989 Toyota Supra 5 speed, has JDM engine swapped using US intake manifolds and other US related electronics and emissions components. The vehicle is otherwise completely stock(even running a OEM paper filter! and OEM exhaust)

When driving, or idling, after 20-25 minutes, the vehicle looses injector pulse, and vehicle dies. It will not restart without a substantial cooldown. The vehicle has great spark while it will not restart. Also has correct fuel pressure.

Injectors are OEM and within spec.
Injector resistor pack is OEM and within spec
Injectors have battery voltage.
CPS is measured at 186 ohms for each pick-up before, during, and after stalling condition.
TPS is measured within OEM spec, and IDL is correctly adjusted
ECT sensor is measured with OEM spec.
Fuel pump is measured at .8-1.2 ohm

I have installed a rheostat in place of ECT to simulate a warmup, without the engine bay heat soak, vehicle does not stall.
All sensors measure the same at the point of stall, not catching a variance.

Engine does not show any DCT.

I've got the big huge Toyota TCCS checker, but it is missing the harness required to plug into this car and use it, anyone happen to have the TCCS harness around?

Any ideas of what I might be missing? Or suggestions of what to check?

 

[Raven97990]

Some additional information I just received from the owner of the vehicle, in summer when temperatures are over 90 degrees, it will not start at all. And he also states he tested for injector pulse then and had not shown any.

 

[MDCmotorsports]

Id say the ecu is junk but im not an electrical expert....

 

[Raven97990]

Id say the ecu is junk but im not an electrical expert....

That is where I am thinking, but it is not common for a Toyota ECU to fail, let alone on a virgin car.

I've added the ignitor ground improvement because i could, still dies once hot.


The only IAT sensor is in the MAF, but it shows normal, nothing out of the ordinary. Besides, a off reading wouldn't kill injector pulse width. Next time it stalls Im going to open the ECU, and trace the injector circuits, to see if it is possible the printed board is lifting the circuit slightly.

 

[Raven97990]

To further add to my confusion, after adding an additional ground to the ignitor... (never mind!)

After adding the ignitor ground the car idled for 1 hour this time before stalling, but just as I was posting she stalled.

So my thought process now is there may be a poor ground, that is over heating the injector drivers.. maybe? Does this thought make sense to anyone else.

Other observations I was able to attain with this stall- The vehicle shows code 14 after stalling, but on cranking shows strong spark. The ignitor is also warm to the touch.

Inspecting the ECU for cold solder breaks, or any deformation of the printed circuit show none, no components are hot inside ECU, no burn smell.

 

[hvyman]

Igniters get really hot normally.

How are the ecu grounds on the intake manifold?

 

[Raven97990]

Igniters get really hot normally.

How are the ecu grounds on the intake manifold?

Just wanted to confirm there are only one set of grounds on the intake. Reviewing the EWD I can only find ground point "b" that goes to the intake. I've done too many 2j's since my last 7m, which have 2 intake grounding points. If it is supposed to have 2, 1 is missing, otherwise, the ground is in great condition, clean, no corrosion and making good contact.

 

[bioskyline]

injector resistor getting warm to??

 

[Raven97990]

Luke warm at best for the injector resistor back, but I show voltage at the injectors during cranking/no start, just lacking the ECU pulsing ground.

 

[Supracentral]

If you have a heat gun, try applying a judicious amount of heat (Within reason, don't melt things...) to the injector resistor pack -- try the same with the ECU.

 

[MDCmotorsports]

If you have a heat gun, try applying a judicious amount of heat (Within reason, don't melt things...) to the injector resistor pack -- try the same with the ECU.

Agreed. Im thinking injector driver part of the ECU, almost the same as a 1j ecu failing with its capacitors.

 

[Raven97990]

Ok then, this car is apparently possessed.

Came in, fired her up and took the heat gun to her. Removed the ECU cover that exposed the component side of things. Got it so hot the back side cover (not getting direct heat) bowwed away from the carriage, and I could no longer hold the ECU. Not a hiccup.

Heat gun to the Ignitor till I couldnt touch, injector resistor until I couldn't stand to touch it, CPS, TPS, MAF until the silicone was almost fluid, nothing.

Direct shot to the ECU temperature sensor and I could hear the engine tone change with the changing mixture.

No stalling at all.

I started wiggling known wire areas despite the harness being in great condition, nothing at all. (CPS connector, harness through firewall, harness over down pipe)

One she hits 30 or so minutes, it dies, loosing only injector pulse. I forgot to bring the spare 7mGte ecu to the shop that I have at the old one, but I really don't suspect it after the heat bath it got without stalling.

Does the ECU have a fail safe if temperature gets too high it will shut off? My gut keeps pointing me at the ECT for the ECU, despite it showing good full range, and simulated with a rheostat the car doesn't stall, so my gut feel is unfounded on any logic, which tends to keep me from putting a new one in.

 

[MDCmotorsports]

Check the grounds for the ECU that should be bolted to the underside of the intake manifold....

If any thing. Put a few more grounds in and around the engine. Entertain me.

 

[whitemike]

This is interesting!

I vote ECU. To me it's the only thing that makes sense due to the consistency of the problem. Just because you couldn't replicate it with a heat gun to the case doesn't necessarily rule out the ECU (does it?)

You say you have a spare? Try it out, let's see what happens..

 

[jdub]

Check for a valid IGf signal from the igniter to the ECU. Do the same for G1, G2, and NE from the CPS.

 

[Raven97990]

At this point I think the weather has gotten too cold, or I have somehow fixed the problem.

After extensive heat soaking of all compensates, it now takes longer for it to stall, but it is also much colder then it has been. After the vehicle stalled last, I confirmed IGF, G1 G2 and NE pulse at ECU, but I do not have a oscilloscope to monitor a signal wave. I cranked once more and confirmed the vehicle would not start, I swapped to a known good ECU and the vehicle fired right up, and ran for 1 minute. I shut the vehicle off, and installed the old ECU and the vehicle also fired right up, and has not stalled since.

Again, this may just be the cold weather, but I'm further baffled. I don't believe a loose wire would be culprit as I had have the original ECU in and out several times, and performed a extensive wiggle test of the wires...

 

[Raven97990]

New information from car owner, when ambient is under 50 degrees, it won't stall and runs perfectly, and only very very rarely after a long drive it might stall.

Could the Barometric sensor be acting up? But that doesn't make much sense, because you'll have heat on of some sorts that would affect the temperature.

Car is inside in the heated garage, with the windows closed blasting full heat.

 

[Flateric]

You say the spark is good, but just double check your CPS and the wiring and connector plug. My car used to totally die when hot and not restart till cool again and it took me months to track it down to crispy CPS plug and wires. Let us know what it eventually is though.

 

[Raven97990]

You say the spark is good, but just double check your CPS and the wiring and connector plug. My car used to totally die when hot and not restart till cool again and it took me months to track it down to crispy CPS plug and wires. Let us know what it eventually is though.

Violently shook then, they are in amazing condition with flexible insulation. The fact I see pulse during no start condition leads me to believe it is not a wire opening when hot.

Can't get the car to stall anymore with the cooler temperatures, this may be something that has to wait until spring to figure out =(

 

[Flateric]

Well I'm both glad for you and also not at all happy. Which is how I'm sure you feel about the situation also, unfortunately.

It sucks because without a clear cut action that lead to this it leaves doubt and uncertainty every time you drive it. It would for me anyways.