Sonic - LONGFT% negative

[Sonic2711]

When I start my sonic at idle is says;

FUEL SYS1 - OL-FAULT
then after a while
LONGFT1 -25.9
SHRTFt1 - 0.0

No Codes except I still get P0304 misfire on Cyl4 after a while.

Cleared and fixed many codes now;
Valve Cover
O2 Sensor
Thermostat and Housing
Fuel Pump
Ignition Coil
Purge Valve

 

[Gobinator98]

Something is making your engine receive too much fuel. Try to have your injectors tested and cleaned especially for cyl 4.


Sent from my iPhone using Tapatalk

 

[Z71]

A faulty O2 sensor (especially the one ahead of the catalytic converter) can cause the engine to run too rich. I had this happen on my 2009 Impala LTZ. changing the pre-cat O2 sensor fixed the problem for good.

Ignition coils on these 1.8 liter engine Sonics are notorious for causing bad misfire and should be the first thing to suspect when a misfire occurs.

 

[Gobinator98]

A faulty O2 sensor (especially the one ahead of the catalytic converter) can cause the engine to run too rich. I had this happen on my 2009 Impala LTZ. changing the pre-cat O2 sensor fixed the problem for good.

Ignition coils on these 1.8 liter engine Sonics are notorious for causing bad misfire and should be the first thing to suspect when a misfire occurs.

Yeah it could possibly be the O2 sensor but not likely. If there was any problem with it, there would be a code. I know that because I had a code for the second O2 sensor but it was not the problem. She definitely should check the ignition coil but since the computer is subtracting that much fuel, it could easily be a leaky injector. But like I told the OP, they need to have someone scan the car and do some testing. Hell, if they don’t have a scan tool already, they could go buy a vci vcx nano for gm cars. It comes with a copy of GDS2(dealership software) which has bidirectional capability. I have one and it takes a little bit to set up but it works wonders for logging data and testing sensors.


Sent from my iPhone using Tapatalk

 

[Sonic2711]

I could really use help here. Dealers just want to keep charging me diagnostic fees and never fix it so I'm trying everything myself.

Dealer initially replaced fuel pump (too hard to do) I suspected they sensed a fuel problem?

I changed the Upstream O2 sensor.
New Coil Pack and Plugs. (this made car run better)
New Purge Valve
New Thermostat and Housing. (was getting a code - now cleared)
New Valve Cover and Gasket (PCV - cleared code)

I'm down to this dreaded P0304 I can't get rid of.

I have done nothing related with fuel but I understand there is a bulletin for carbon cleaning - upper engine. Maybe Cam sensors?

I have a code reader. And other than the code, I am getting super negative LONGFT1% and FUEL SYS1 - OL-FAULT

This forum is all I got. I am stumped.

 

[Gobinator98]

I could really use help here. Dealers just want to keep charging me diagnostic fees and never fix it so I'm trying everything myself.

Dealer initially replaced fuel pump (too hard to do) I suspected they sensed a fuel problem?

I changed the Upstream O2 sensor.
New Coil Pack and Plugs. (this made car run better)
New Purge Valve
New Thermostat and Housing. (was getting a code - now cleared)
New Valve Cover and Gasket (PCV - cleared code)

I'm down to this dreaded P0304 I can't get rid of.

I have done nothing related with fuel but I understand there is a bulletin for carbon cleaning - upper engine. Maybe Cam sensors?

I have a code reader. And other than the code, I am getting super negative LONGFT1% and FUEL SYS1 - OL-FAULT

This forum is all I got. I am stumped.

Since you said it only has the misfire code for the #4 cylinder, it couldn’t be the fuel pump, O2 sensor, anything coolant related or even a bad coil pack.

It would have to be something specific to that cylinder, such as a bad spark plug or bad injector. But since you said you replaced the spark plug, look into the injector.

If you got a flat head screwdriver handy, hold it to the injector and put your ear to the screwdriver. Compare the injector tick between the four cylinders and that should give you a good idea if it is stuck open or closed but I don’t think it will tell you if it is leaking.

Could always replace just that injector and see what happens. You might also want to think about replacing them all soon if the # 4 injector I is the cause of the misfire, they are all the same age and might go out at similar times.

Cam sensors would throw their own code and could cause a non start issue, all cylinder misfire, or both.

Where are you at if you don’t mind me asking? I live in southwest wisconsin and if you are near I could definitely help you diagnose the issue further with my dealer level software/scan tool.


Sent from my iPhone using Tapatalk

 

[Sonic2711]

Thank you for the reply! Car was initially dead. Friend said bad fuel, drained and refilled. Got it started. Still had blinking check engine light and traction light. Changed coil pack and plugs. Changed to Solid Check engine light but ton of codes. Took to dealer - they replaced the fuel pump. I cleared each code out with repairs mentioned. All codes now cleared except for P0304 along with the negative fuel trim (running rich). Car runs very well now - except at idle it does seem to not idle perfect. Have spent a ton of time trying to figure this out. Dealer is no longer an option.

I'm in Detroit area - but thank you. I am eager to figure this out. I appreciate your help!