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Fuel map randomly goes extremely rich causing car to shut down.

Off Topic Discussion

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Hi guys I need some brains. I'm having a strange issue with my 88 Rx7 t2. It has a adaptronic ecu, Id750, Id1000 injectors aem smart coils. Upgraded fuel system. Just naming some mods for an idea what I'm working with.

Anyways, iv been dealing with This issue randomly for a while. When it used to run, it would randomly shut down out of nowhere without restarting. Could never figure out what the problem was. But just recently figured out what the issue is. I just don't know what is causing it.

The only way I could get the car to start and run properly was to decrease the whole fuel map percentage by about 40% which brings the afrs to a normal reading as it should be .

But i don't understand how because when the car used to run on the same map before decreasing the fuel map. The afrs and fuel was fine. But now seems to be extremely rich, causing my car to flood I guess and shut down/not start.

I havnt been able to figure out why it becomes so rich on the same fuel map that I used to drive all the time.

I could easily just retune the fuel map so the car runs again but I'm scared to decrease the fuel map and then all of a sudden the car snaps back to how it used to be and the car would lean out and destroy my motor.

If anyone has any idea what's going on please help me out!! Thanks guys. also I just replaced the injectors and it didn't do anything to help the issue.

At the risk of suggesting the obvious, has the base fuel pressure changed at all? Or any possibility there's a blockage in the return line or a failed fuel pressure regulator?

I have a gauge on my FPR and the pressure is normal and it hasn't changed from when it was running normal. If the fpr was failing or line was restricted wouldn't it show on the gauge?

Which Adaptronic ECU have you got in there? Can you log some parameters? In particular, have a look to see if any huge fuel trim values are active. a faulty coolant or intake air temp sensor, or wiring, might cause some really odd fuel trims to become active.

It's the adaptronic select e420d. And the temps are reading normal also tps seems to be working properly. And iv been going over the wiring and haven't found any issues.

I've had issues with a couple of odd-ball ECUs where a table would get corrupted and mess up the fueling. In one example, it was a learned-fuel table (essentially a long-term trim derived from closed loop operation). The other was when the calibration table for the Lambda sensor was corrupt and closed loop just kepts adding fuel.

The advice to log fuel trims is the right approach -- you are fixing the symptom. Could be injector dead-times, battery voltage, some compensation which had bad data from a failed sensor (I've seen a bad TPS look like full-throttle -- which could cause too much fuel).

Make sure every sensor has a reasonable value and visit every table or calibration to make sure they look OK.

Good Luck!

Have you checked the coolant temp (or air temp) fuel enrichment tables?

Temperature based fuel trim tables.

I have a client for which we made a PnP harness for his Lotus Elise that encounter this exact, same issue with his M1200.

What I was able to gather was that the MAP, for one reason or another, might read ~2psi on key on, and it stays this way for some time, then it just randomly reads correctly. I tried to contact Adaptronic but they didn't really understand my issue and my client deals with this by pretty much not using the car.

If you can log this condition I'm sure they would be interested to look into it for you.