2G 6Bolt swap idle goes rough a few seconds after start.

[mihai clotan]

This is a problem that has been stoping me from finishing this project. The motor has been re-done, but i cant get the car to run good. It starts on the dime, idles good for few seconds, than goes rich..than lean ..than rich again, i get unburned fuel coming out of the exhaust, idle turns rough.
- I checked vacum's, gas, wiring of cas, its all good.
- I had guy's who swear they can fix it in a minute, and end up scratching their heads.
- Everything that is available here, on the forums, i have or someone else has tried ....we replaced injectors, we replace fuel pump, pressure regulator , firing order , injector oder.....

This is the problem i think i have : the motor is a 92 6 bolt, the ECU 96, the car 99 GSX....cams are GSC S2....between the timing, the injectors and spark there is no good communication.
If anyone here know's how to set this things for my specific set up , will be a sooo helpful.
Thank you.

 

[1davho]

I would start by checking your o2 sensor. Do you have a way to log it and make sure it is switching like it is supposed to?

 

[954g63gst]

My car did that. I ran a boost leak test and found my throttle body shaft seals were leaking. Have you done a boost leak test?

 

[mihai clotan]

I am not sure what u mean by logging the O2, but on a scanner tool it did pull a O2 code ....
boost leak's, i did have a guy with a weird machine with ear muffs and a microphone , go around the motor and listen for air leaks....he found some , one was at throttle body. I did fix them , however i never replaces seals on throttle body.
There is one more issue that bugs my mind, at idle things go a little rough but if i apply throttle, motor gets flooded and dies..... i'm thinking CAS is malfunctioning!!!!!?

 

[WES_393]

I am not sure what u mean by logging the O2, but on a scanner tool it did pull a O2 code ....

Was the code for the Upstream O2 sensor? That could easily be the problem. The ECU adjusts fuel delivery based on the front O2 sensor readings. It's normal for the A/F ratio to oscillate since the O2 voltage cycles around stoich (14.7:1).

But if the AFR is swinging drastically, the exhaust smells like fuel, the engine runs poorly, and the ECU is throwing an Upstream O2 sensor code... Then I'd replace the front O2 sensor.

 

[1davho]

Yeah, if it is throwing a code for the o2 sensor, change it. Make sure the code says bank 1 sensor 1. That is how you know it is your upstream sensor.

 

[mihai clotan]

the codes are bank1 bank 2 and something related to thermostat if i remember correct ..i kept checking wiring and vacuum , and i found some vacuum leaks ..i fixed them an i replaced the 780 inj for stock ones ....the results are : the car starts perfect , idles perfect for about 20 seconds ...than starts getting rich and looses its idle
i realize the water neck connections do not match the harness wiring , therefore are not connected , hence the fans do not work ( i have a big shop fan in front of the car)
also i read somewere the temp sensor may influence the ecu to run rich.
my concern is the water neck pipe that comes from radiator , i dont think is the one this car should have , or i need to make some mods that i am not aware of

 

[mihai clotan]

The problem was a shorted knock sensor wire. Not having the right scanner tool or tuning solution made it imposible to detect.