When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
ive got more research to do - but my gut is shifting to ECM failure/corruption. I reached out to Relentless Motorsports in TX to see what issues they've seen with ISF ECMs as it seems as if they've done at least one ISF ECU already.
but know I have zero evidence that it is the ECM at this moment.
Ray call this a hunch - but with the recent service you listed it sounds like the previous owner / shop was trying to solve a mysterious stall and threw some parts at it and the seller got frustrated and just sold it. Who did this recent service work? Was it done before you bought the car? If the dealer did the work - do you have the paperwork? Does it list the reasons why those parts were installed?
We've been messing with my wife's ISF for over a year now and just recently went through a bunch of service/parts in an effort to get it to stop stalling and we're still scratching our heads.
Hey Sorry for the late response but i thought i have solved the issue by changing out my crankshaft position sensor, which seemed to do the trick drove it for around 20-30 miles no issue what so ever, then it start to fluctuate rpms after my second drive at a stop after about a 25min drive, but nothing happened , then 5min later it stalled at a red light, but started right back up again and nothing happened for the remainder of the 15min drive with countless stoplights, got back in the car around 3 hours later and made the same drive home and nothing happened. So it is definitely not happening at the same time anymore, now it seems like it is completely random once warm, and has only happened once in about 75 miles, (I bought a DENSO crankshaft sensor). I am honestly out of ideas now I have no idea what is happening, I look forward to your update
We're at a point where we are about to throw in the towel. Running through a few more ideas.
As Lobux had suggested (and at one point I suggested) it could be the ECM.
It could be the engine wiring harness (it lives its life in an OEM heat trap at the top of the motor with a stupid plastic cover over it) that also lives inside of a plastic harness guide cover
It also could be one of a number of faulty sensors with an (occasional) internal short that causing the PCM to lose connectivity.
The last idea I may toy with is placing an endoscope inside the intake and watch the throttle body to see if it somehow slams shut right before a stall (indicating that the ecm gave up or a connection weakened with the throttle body) - still that doesnt explain the lean condition leading up to it.
The one thing this entire process has taught me is how incredibly, needlessly over engineered these cars are. When they can fail in such a way that $6800 in expense across a dealer and 2 Toyota/Lexus specialty shops that can't track the problem down then what is the point of making them so complicated?
If I find anything else I'll let you know - but if I tag out this might be on you.
I hear the new Tesla Model 3 Performance is awfully nice this time of year....tax incentives and all.....
I had one of my mechanic friends come over try and diagnose the car for a few hours, he had suggested that it had to be a sensor and it was either the Crankshaft sensor , ECT sensor or both, as I have replaced the crank sensor and have noticed the stalling is random now, not just as soon as it gets warm, i might go ahead and replace the ect sensor to see if that could be the last of my issues, do you think throwing this sensor at it is a waste of time or worth a shot?
If you have checked the wiring carefully and found nothing, it might be a good idea. I have a long troubleshooting story about an intermittent problem I had with my Supra. It took a year to figure it out because ultimately, the pin in the connector to the ECM was not connecting until the cabin temperature got above 50F. I spent a lot of money on parts thinking the parts were at fault, but in the end it was the pin in the connector. I was able to fix the pin by backshelling it, and the problem has never returned, but I was tearing my hair out to find this. The car was a little over 10 years old at the time, and I really started hating to drive it because it was so annoying - dash lit up like a Christmas tree, but a restart made everything go away. Never happened in summer, only when the temperature got below 40F, and once it got even a little warm in the car, no problem to find. I ended up letting the car sit outside, get cold, and didn't start it until I had chased the signal with a meter all the way back to the ECM. I took the cover off the ECM and validated the signal was present inside, but was not present outside, and that's what finally tripped the trigger to the fix. I'll be the first to say I wasn't very happy, but after putting every component in the chain in my freezer and getting nowhere, I was only left with wiring, and even then, it wasn't obvious like a damaged harness or broken connection, and believe me, I tested EVERYTHING in the circuit.
I'm not saying this problem is the same, but it really sounds similar, especially with the initial thermal response, and now with the randomness. When I replaced all my timing chains and their associated tensioners last September, my car was only running on one bank of cylinders on initial startup. I unplugged and replugged all the ECM connectors and everything got better right away. So, if this were mine, that's where I'd be looking - connector pins, especially at the ECM.
So what do you think the best course of action would be next? Should I start testing the ecm connectors after the car is warm (if that is possible) should I take the ecm out and have a specialty shop look at it, or should I just take it to a shop and have them test the ecm and connectors (not sure how much that would even cost). By the way I dont have any of the special tools associated with wiring or any testing probes, all I would be able to do at the moment is check for corrosion and loose connectors.
Also i noticed i didnt mention before the previous owner also put an RR racing tune on the car, but it was not recently, could that have effected the ecm to cause an issue like this?
So what do you think the best course of action would be next? Should I start testing the ecm connectors after the car is warm (if that is possible) should I take the ecm out and have a specialty shop look at it, or should I just take it to a shop and have them test the ecm and connectors (not sure how much that would even cost). By the way I dont have any of the special tools associated with wiring or any testing probes, all I would be able to do at the moment is check for corrosion and loose connectors.
No, just disconnect and reconnect all the ECM connectors. That's where I'd start.
No, just disconnect and reconnect all the ECM connectors. That's where I'd start.
ok I’ll start with that, is there anything special I have to do for this to not permanently mess anything up, should I disconnect the battery? And do you possibly have a diagram of where the ecm is and exactly what connectors I should unplug?
04-13-24, 11:43 PM
