Stalling problems, rough idle & Fuel trim problems

[config]

I'm no mechanic and am having problems understanding this. Vehicle has been running rough. Changed the plugs, wires, O2 sensors and it helped a bit but still has stalling, rough idle (when cold) and bad gas mileage. Purchased a scanner and here is what I got. I don't understand what would cause Banks 3&4 to have -100% fuel trim readings. Again, there are no codes stored. Am I reading this right? Please see attached document for more sensor data.

Requesting MIL Status & DTC Count
TX: 0101
RX: 41010007E505
MIL: Off
Stored DTCs: 0
Requesting List of Stored DTCs
TX: 03
RX: NODATA
No stored trouble codes found.
Requesting List of Pending DTCs
TX: 07
RX: NODATA
No pending trouble codes found.
Checking for Freeze Frame Data
TX: 020200
RX: 4202004C51
Freeze freeze data found for C0C51
Freeze Frame: Reading Fuel System Status
TX: 020300
RX: 4203001900
Fuel System 1: OL
Fuel System 2:
Freeze Frame: Reading Calculated Load
TX: 020400
RX: 42040000
Calculated Load: 0
Freeze Frame: Reading Engine Coolant Temp
TX: 020500
RX: 42050016
Engine Coolant Temp (F): -0.399999999999999
Freeze Frame: Short Term Fuel Trim (Banks 1,3)
TX: 020600
RX: 4206007F
STFT Bank 1 (%): -0.78125
STFT Bank 3 (%): -100.78125
Freeze Frame: Long Term Fuel Trim (Banks 1,3)
TX: 020700
RX: 420700B2
LTFT Bank 1 (%): 39.0625
LTFT Bank 3 (%): -100.78125
Freeze Frame: Short Term Fuel Trim (Banks 2,4)
TX: 020800
RX: 42080080
STFT Bank 2 (%): 0
STFT Bank 4 (%): -100.78125
Freeze Frame: Long Term Fuel Trim (Banks 2,4)
TX: 020900
RX: 42090080
LTFT Bank 2 (%): 0
LTFT Bank 4 (%): -100.78125
Freeze Frame: Intake Manifold Pressure
TX: 020B00
RX: NODATA
Freeze Frame: Engine RPM
TX: 020C00
RX: 420C000000
Engine RPM (rev/min): 0
Freeze Frame: Vehicle Speed
TX: 020D00
RX: 420D0000
Vehicle Speed (mph): 0
Freeze Frame: Ignition Timing Advance
TX: 020E00
RX: NODATA
Freeze Frame: Reading Monitor Test Results
TX: 0101
RX: 41010007E505
Misfire Monitoring Supported?: Yes
Misfire Monitoring Completed?: Yes
Fuel System Monitoring Supported?: Yes
Fuel System Monitoring Completed?: Yes
Comprehensive Component Monitoring Supported?: Yes
Comprehensive Component Monitoring Completed?: Yes
Catalyst Monitoring Supported?: Yes
Catalyst Monitoring Completed?: No
Heated Catalyst Monitoring Supported?: No
Heated Catalyst Monitoring Completed?: Yes
Evaporative System Monitoring Supported?: Yes
Evaporative System Monitoring Completed?: No
Secondary Air System Monitoring Supported?: No
Secondary Air System Monitoring Completed?: Yes
A/C System Refrigerant Monitoring Supported?: No
A/C System Refrigerant Monitoring Completed?: Yes
Oxygen Sensor Monitoring Supported?: Yes
Oxygen Sensor Monitoring Completed?: Yes
Oxygen Sensor Heater Monitoring Supported?: Yes
Oxygen Sensor Heater Monitoring Completed?: Yes
EGR System Monitoring Supported?: Yes
EGR System Monitoring Completed?: Yes

 

[dogfriend]

I don't understand what would cause Banks 3&4 to have -100% fuel trim readings

If you have a leaking intake manifold. It will make the engine idle rough when cold. The fuel trim will be thrown off because the PCM is trying to compensate for the extra air leaking in.

 

[Phredawgy]

If you have a leaking intake manifold. It will make the engine idle rough when cold. The fuel trim will be thrown off because the PCM is trying to compensate for the extra air leaking in.

Or a vacuum leak in one of the hoses.....check the underside of the PCV elbow that goes into the intake manifold (not a bad idea to check all the hoses) Could be the beginnings of your IAC Valve taking a poop on you as well.....or all of the above

 

[config]

If you have a leaking intake manifold. It will make the engine idle rough when cold. The fuel trim will be thrown off because the PCM is trying to compensate for the extra air leaking in.

What's the simplest way to check/test this? How complicated is it? I've searched and seen the pics & instructions on a SOHC but how about a OHV?

 

[dogfriend]

Two ways that I know of to test:

Some shops may have an ultrasonic vacuum leak detector. Basically, this device can "hear" the hissing noise caused by a vacuum leak and can help you pinpoint the location. I have seen these for sale, but they are too expensive for the home mechanic.

http://www.reliabilitydirect.com/ultrasoundproducts/leakdetectorindex.htm

Another method is to use an unlit propane torch. With the engine idling, you direct the propane to the locations where you suspect a leak. If the propane gets sucked into the engine, it will momentarily raise the idle speed confirming the existence of a leak.

 

[NHale623]

Unless it's huge, a vacuum leak typically will not cause rough running. You'd also have DTC's set.

When was this data captured? Was the engine even running?

These two pieces of data jump out at me:

Engine Coolant Temp (F): -0.399999999999999
Engine RPM (rev/min): 0

 

[config]

Unless it's huge, a vacuum leak typically will not cause rough running. You'd also have DTC's set.

When was this data captured? Was the engine even running?

These two pieces of data jump out at me:

Engine Coolant Temp (F): -0.399999999999999
Engine RPM (rev/min): 0

I think that capture was all bad. The engine was running. The attached file has better data.

Anyhow, I just read a post where the individual was having similar problems and it appeared to be his Apten chip was causing it. Well, I had a Superchip installed so I inspected it and it did have some corrosion on the connections. I took it off for the meantime so I can see how it runs tomorrow morning while it's cold and been sitting there. I'm keeping my fingers crossed...