i have a 92 1.6 my car loads up like it getting way too much fuel at low rpm and once it hit higher rpm clears out. it would do this when it was cold but since i put the header on it now only does it when heated up and idles perfect, ive already lost my mind over this. things ive replaced coil pack, plugs an wires, mass air flow sensor, o2 sensor,temp sensor, idle control valve, ignition chip, fuel injectors, fuel pressure regulater, fuel filter, fuel pump and also the ecu. someone has told me since i have an after market header the o2 sits to far back from the collector to heat up properly, is this true? and also ive read about a 4 wire conversion instead of getting a new bung welded closer to the output of the head. any ideas or suggestions? sorry for the long post thanks for any in put or feed back.

 

I suppose you could try the 4 wire 02 sensor but mainly it just heats up faster allowing car to get into closed loop faster although if your stock sensor isn't getting up to temp then it could be the ticket, about how much farther down your exhaust is the o2 sensor compared to factory. mind saying what other mods you may have how many miles etc... Have you checked for vacuum leaks and have you checked compression?
When you say higher rpms do mean like 3500 or like 6000? more specific please

 

its about 18 to 20 '' further back than stock. just the header, exhaust, and air filter. i have about 110,xxx on the motor the, car itself has about 155,xxx. it clears out at about 3200 rpm. it only really does at pretty low rpm, 1500 - 3000 rpm. i did do the 4 wire o2 last night and it help a lot but did not solve the problem.

 

pull your plugs and check color(grey black white)... check ignition timing also.. most people seem to be pretty happy around 12*btdc after that there isnt much else... check for vacuum leaks(if you dont know how click here http://tinyurl.com/3d25pnu)

 

Get header wrap and wrap that thing. I had to do this to my Nissan for the exact same reason. That way the heat will stay in the pipes and get back to the O2 rather than dissipating into your engine bay.

 

so i took it a shop finally to get it check out cause i have tried everything i can do. i guess i will find out soon . i will post the results as soon as soon as they come in, thanks for the support!

 

so some how there was air getting in to my fuel system in some impossible place to find. it wasn't leaking or anything like that. it took 4 days to find this problem, but now its good to go,up and running again. car runs perfect now!

 

could you specify where exactly the air was getting in? I have the same year car and the same problem but i have more or less fixed it with still a very slight hesitation when cold at low rpms and better when hot but still hesitates at low rpms. Maybe you can take me to your mechanic and he can do a quick check for me since he just did yours.

 

It was in the fuel tank it self. who ever i got the car from lost the bracket for the pump and just zip tied it in. Right before my friend sold it to that guy he had put a walbro 255 in the car. But when i got car there was no walbro 255. It really kinda burned out the pump, but not all the the way it was still semi working, i had to replace it. The pump wasn't building up enough psi. I believe oem spec psi is 31. Mine was at 24 psi. When you would pinch off the return line the psi would stay at the same pressure. It wouldn't build up any pressure. Hope this helps some. The name of the place was PAW it in la mesa. CA.