stumbling issues

[buzzbomber]

ok guys i have an 89 n/a 5spd only mods is exhaust and intake.
problem arrizes only when the engine is warmed to temp after driving for a while and when it reaches that no matter what speed i'm at or gear it starts to surge and buck like its throwing the tps into a wierd loop with a/f mixture and making it flood. not sure whats up. no matter what i do with the throttle it still does it. i can shut the key all the way off while coasting or stopped and start the car and put it in gear and it runs fine for a few min. and then does it again. car runs great until it warms up. my thoughts are that its the o2 sensor but what do you guys think?

 

[AJ'S 88NA]

ok guys i have an 89 n/a 5spd only mods is exhaust and intake.
problem arrizes only when the engine is warmed to temp after driving for a while and when it reaches that no matter what speed i'm at or gear it starts to surge and buck like its throwing the tps into a wierd loop with a/f mixture and making it flood. not sure whats up. no matter what i do with the throttle it still does it. i can shut the key all the way off while coasting or stopped and start the car and put it in gear and it runs fine for a few min. and then does it again. car runs great until it warms up. my thoughts are that its the o2 sensor but what do you guys think?

Sounds like maybe the ISC. Have you checked for codes? Or CSI stuck.

 

[buzzbomber]

well csi i dont think would cause it since it goes out of loop after like 2min. and it runs fine if its shut off and started back up. my other guess is it may be the coolant temp sensor

 

[cuel]

Check for codes?

http://cygnusx1.net/Supra/TechTips/engine_error_codes.aspx

 

[AJ'S 88NA]

I think if the CSI isn't working right it could keep adding extra fuel after warm up causing it to run rich and stumble. And like I said and cuel said check for codes.

 

[CRE]

The Cold Start Injector is ONLY powered when the key is at ST1 (while you're actively cranking the engine). After that, if it's adding fuel, it's outright leaking. http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=038

What you're describing sounds like what my AFM was doing when it died. There was a break in a circuit which didn't sever the trace until the AFM heated and parts expanded. I only managed to find it without a doubt by testing the pins while constantly heating the AFM with a hair dryer... after a certain temp, nada. Heh, I got a lot of funny looks on here and SF about that... but it worked.

Other possibilities are:
the ECU's coolant temp sensor
knock sensor or wiring
TPS
AFM or harness wiring specifically to the FC switch


You have any error codes?

 

[buzzbomber]

well the check engne light hasnt came on so i havent chcked for codes but i can do that. is there any way it could be a bubble in the coolant system?

 

[AJ'S 88NA]

You could still have a code without the light on.