Reving problem when 4EFTE it's cold

[chrismgnsGT]

Hello to all starleteers, so i have a very strange issue on my GT that really makes
me crazy. When i start the engine and the car it's still cold, i rev up but the engine
works like -1 cylinder. So, after 5 minutes when it's a little bit warm magic happens,
the engine runs perfect without problem ! So, i take every part that could be
responsible for this and still i'm not found anything, problem is on. Here is a list
with my moves..

New Oxygen Lamda Sensor
New Cold start valve (Green)
New Temp valve
New spark wires
New sparks
New fuel filter
New fuel pump
Cleaning throttle body and throttle sensor
New Water fluid/Oil

Also, i give a check on my compression and it's superb and my camshafts it's on the right
place. I don't get any fault codes. I don't know if i miss something else ! If someone knows something about
this, i would really appreciate to help me with this strange issue.

Thanks,

Chris

 

[Jay]

It's a bit of a long shot but seeing as you have ticked so many of the normal boxes..

The waxstat could be dead or dying. It's part of the throttle body which controls cold idle air feed. As it heats up the additional airflow that the vehicle needs when cold is decreased. My guess is that it could be stuck closed meaning your cold idle isn't 100%. Soon as the vehicle warms up everything is fine.

Might be worth checking.

Jay

 

[chrismgnsGT]

Dear Jay,

thank you very much for your response. When you said waxstat do you mean the choke or no? Sorry but i heard it for the first time and i don't understand where is this part. My throttle body have only the throttle sensor
wich comes with a fuse on it and nothing else so if you can please help me understand where this part is to give it a check (maybe a picture from google). I forgot to tell that i've changed idle control valve too. I have pretty normal idle and the problem appears only when i push the throttle violently, when i do that it starts to hesitate and then revving
up normally and after few minutes when choke is gone and engine is a little bit warm everything works fine.

Thanks,

Chris

 

[gorganl2000]

hard to tell as you seem to have covered a lot already
but how's your distributor/cap? maybe igniter and coil?
any moisture getting into/onto these?

 

[Rev]

A similar issue arises when I lean out the safc2 'high' map at idle, the engine dies for about 5 secs in colder weather on cold start as fueling is too lean.
I have a 2 wire o2 sensor this does not function till heated up so is very effected by my the fuel map tweaks and well because open loop applies on start up. If you have a 3 wire o2 maybe check the heater wiring?

Map sensor tubing and inlet vacuum hole being very clean so the map reads properly is another suggestion there maybe a map line filter to consider.

 

[chrismgnsGT]

Happy news for my starbo guys. I think something from all of these things that i've changed on my engine solve this stupid issue. After all, my mind goes to injectors (that was the only thing that i'm not checked), maybe something stuck over there on one of my injectors and now with the new fuel pump and fuel filter, the fuel and all the circuit works better and more powerful so finally dissapear this possibly junk. I wanna thank all of you for your answers and help about my baby's issue.

Cheers,