impala 2000

[specialist]

Hi you all,

I have an impala 2000 3.8 L 75 k on it.This car when it is started for the first time after sitting for a moment it starts misfiring like it is not getting enough fuel and then cuts off.It start ok again and if i hold the gas pedal the engine keepson running but very bad.After a while holding gas pedal steady it start running fine untill it sets for a moment again.There is no smell off fuel,fuel filter has been change,fuel pressure regulator valve,map sensor,coolant sensor and air filter.Fuel pressure read 45 psi,i don't know if it is the correct reading.

any help please.

thanks,

[57chevyragtop]

Check for vacuum leak(s) then go to plugs and wires and check those for crossed or broken wire(s). You didn't mention if your throttle body was cleaned or not so be sure of that as well.

[specialist]

Originally Posted by 57chevyragtop

Check for vacuum leak(s) then go to plugs and wires and check those for crossed or broken wire(s). You didn't mention if your throttle body was cleaned or not so be sure of that as well.

Hi,wires and plugs are new.No, i didn't clean the trotle body,tomorrow i will do it and see what the result are.I will keep post.
thanks,

[57chevyragtop]

I like to use WD-40 and paper towels for throttlebody and both sides of butterfly. These can be quite dirty so be careful not to let dirt migrate inward. MAP sensor screen can get pretty dirty as well but you mentioned yours was new...new wires and plugs...ok, still would be good idea to double check for crossed wire(s) I've done it (my 3400) and I think everyone I know has. It's soooo easy to do and you swear you got it right the first time then oops!

[specialist]

Originally Posted by 57chevyragtop

I like to use WD-40 and paper towels for throttlebody and both sides of butterfly. These can be quite dirty so be careful not to let dirt migrate inward. MAP sensor screen can get pretty dirty as well but you mentioned yours was new...new wires and plugs...ok, still would be good idea to double check for crossed wire(s) I've done it (my 3400) and I think everyone I know has. It's soooo easy to do and you swear you got it right the first time then oops!

I cleaned this morning the trottle body.I took it off to do a better cleaning.Putit on again,start engine and after a few minutes at idle it start doing the same thing again.When itstart doing it,you can hear a very heavy air suction and then it cuts off.I unplug the oxygen sensor ans start again and untill now no more cuts of or miss idle behavior but the check engine light is on due to the disconnect o2 sensor.

thanks,

[57chevyragtop]

really didn't need to take off the throttlebody to clean but that's ok. unplugging the O2 sensor has me a bit miffed as to why it would run better in doing so? could be a bad O2 sensor I suppose but seems unlikely if light was not on when connected...have you tried unplugging the MAP? with the O2 pugged in.

[specialist]

Originally Posted by 57chevyragtop

really didn't need to take off the throttlebody to clean but that's ok. unplugging the O2 sensor has me a bit miffed as to why it would run better in doing so? could be a bad O2 sensor I suppose but seems unlikely if light was not on when connected...have you tried unplugging the MAP? with the O2 pugged in.

Hi good morning,
I have a new o2 sensor on and a new map sensor to.I have not unplug the map sensor, but i can try it i have nothing to loose.

thanks

[wafrederick]

It could be bad coil also.You can replace one coil one at a time.Be carefull,pull one plugwire off at a time at the coil with plugwire pliers.

[specialist]

Originally Posted by wafrederick

It could be bad coil also.You can replace one coil one at a time.Be carefull,pull one plugwire off at a time at the coil with plugwire pliers.

The coils were replace by the owner,so they are new.Today the owner took his car and will drive it for a few days.

thanks,