Help: Having problems after resetting ECU

[suprajjang]

I have a 91 5spd supra. Current mods are bic ddp, blitz catback, hks ssq bov, apexi intake, and cooleeze IC hardpipes. After installing the hardpipes i went ahead and reset the ecu by pulling the efi fuse for about a minute. When i first start the car, it idles around 600-700rpm which is normal. Now when i go to drive the car is when problems occur. The car is fine until i start to slow down. When i come to a stop the car wants to die. the rpm drops to like 200 and then comes up to 400 which is still too low. Now i know this is low but i have no idea why its doing this. When the rpm gets low the check engine light comes on but once the rpms go back up to 400rpm the check engine light goes away. After resetting the ecu i drove the car for about a hour and half for the ecu to learn the new setting. Now the last time i reset the ecu i only drove the car for about 30 minutes and the car seemed fine after that so whats causing my car to almost die when i come to a stop? Also before i reset the ecu the car was normal idling cold around 1200 and then dropping down to 600-700 when warm. also before resetting the ecu the rpms never got below 500 coming to a stop.

 

[robbo185]

is your bov recirculated? if not there is your problem most likely

 

[suprajjang]

its not recirculated but i was not having problems before i reset the ecu. The car was running great until i pulled the efi fuse so there has to be another reason why the car wants to stall

 

[mkiiSupraMan18]

Clutch pedal feel a little "limp"?

If you don't think it's the BOV, make sure your clutch is fully engaging/disengaging I know you didn't mess with it, but it could just be a coincidence. Just throwing it out there.

Also, I'd give it a bit more drive time. Just give 'er a little gas when ya come to a stop. Also is this from a gradual stop (downshifting letting off the clutch) or a sudden (3500 rpm push the clutch in and roll to a stop, put in first and drive off) ?

 

[Supracentral]

Some MKIII's are more 'stubborn' than others when it comes to learning the base. And with some cars, the farther you are from stock, the longer it takes for it to learn.

Be sure to vary the driving while you are trying to get it to learn. Some highway time, some stop & go traffic light time, and if you can find a place, some curvy road on and off the throttle driving as well.

My old 90T used to be a real bastard about this, it always took it a couple fo days to get itself straight after an ECU reset.

 

[MDCmotorsports]

You know I have the same problem, and I've put 500 miles on the car since pulling the efi.

Ive also tried other bovs including recirc.

Nothing has helped.

Sometimes the car wants to behave and idle right at 750-800, other times it struggles after a long highway cruize and wants to idle at 400.

 

[Nick M]

After installing the hardpipes i went ahead and reset the ecu by pulling the efi fuse for about a minute.

Pulling the EFI fuse only clears DTC's and erases short term fuel trim. Shutting your car off also clears short term fuel trim.

If you don't pull the EFI fuse, the car should still react and relearn.

 

[mkiiSupraMan18]

^ so you have to unhook the neg battery terminal to reset the computer like a hard reboot, pulling the fuse is more like just logging out of windows?

* edit*
I would have thought both done the same.

 

[Nick M]

Pulling the EFI fuse and pulling the negative do the same thing to the ECU.

 

[mkiiSupraMan18]

Cool beans, I thought right then... I'm writing this down. :icon_bigg

 

[suprajjang]

Clutch pedal feel a little "limp"?

If you don't think it's the BOV, make sure your clutch is fully engaging/disengaging I know you didn't mess with it, but it could just be a coincidence. Just throwing it out there.

Also, I'd give it a bit more drive time. Just give 'er a little gas when ya come to a stop. Also is this from a gradual stop (downshifting letting off the clutch) or a sudden (3500 rpm push the clutch in and roll to a stop, put in first and drive off) ?

i dont think its the clutch pedal. Also even if i give it little gas the rpms drop to like 200 and come back up to 400 so that hasnt helped yet. it does it no matter how i stop, i can use engine braking and once my rpms is about 1000 i press the clutch pedal and the rpms drop down too low and when i push the clutch in at around 2500 rpm the cars rpm drops down way to low. wierd thing is that sometimes it idles at 600-700 which is normal and sometimes it fights to keep the engine running but it dies so im just confused at the moment

Be sure to vary the driving while you are trying to get it to learn. Some highway time, some stop & go traffic light time, and if you can find a place, some curvy road on and off the throttle driving as well.

I drove on the highway for about 45 minutes and then did city driving for and then another 45 minutes in the city so i wonder how long it might take but i guess ill do another round of driving tommorrow



Only reason i pulled the efi fuse is because some of my old IC hoses had big cracks and holes so i thought that was making my car run really rich and i was getting 12mpg so i pulled the efi fuse and now im having idling problems

 

[mkiiSupraMan18]

check all your Vac lines ?

 

[suprajjang]

just drove another 2 hours today. died only once and its running lot better then yesterday but not good enough. it doesnt drop down to 200 anymore but now it drops to 400 so its getting better.

 

[suprajjang]

I found a solution. Drive with your AC on and the car will never die:biglaugh: and the RPMS never go below 600