McQue
NAXJA Forum User
- Location
- Plainville, Connecticut
sending the fuel trim article to your gmail address as a pdf document
For some reason I feel a leaking injector would show up on its respective spark plug.
Have you probed the manifold flange with carb cleaner?
Thanks, it's a good read.
I'll have to disconnect some of my injectors while idling, and pressurize when pulled out and still connected to the rail to see if it confirms my suspicion of a leaking injector (s).
Injectors, O2 sensors, radiator. I feel it has to be one of these 3 components causing the problem. Likely first two, but I'll keep the radiator in mind.
I'll also check my IAT/MAP/IAC/TPS to make sure all are responding correctly and aren't dirty/malfunctioning. Worth a check.
Are you sure it is not a wiring/connector/ or O2 heater issue?
I pulled the injector assy tonight. Was able to find as well with all of that out of the way that two of the exhaust manifold bolts weren't even finger tight (one between cylinder 3 and 4, exhaust manifold only bolt and other exhaust manifold only bolt, by cylinder 6). Tightened everything back up after a thorough visual inspection and then re-installed 6 new bosch injectors.
After install I reset KAM and then took her for a ride. LTFT's have gotten better, but still at -7%. Something at idle still isn't right.
So I believe I can rule out any issues with the injector assy, and any exhaust leak at the manifold/head/Gasket area.
I'll have to check for hairline cracks in the exhaust system this weekend, including where the two pre cats merge together. Didn't get a chance to test for exhaust leak there tonight.
O2's are still on the list for the weekend too, either re-test and verify or just flat out replace all 4.
Sent from my SM-G900V using Tapatalk
...The two O2 sensors after the final Cat converters are just EPA verification devices that the engine and Cats are performing as designed to not emit excess HCs and NOx gasses by measuring for too little or too much O2...
FYI - here is a cut and paste from my 01 FSM...
Downstream Sensors:Two downstream sensors
are used (1/2 and 2/2). The downstream sensors are
located in the exhaust downpipes just after the minicatalytic
convertors. The downstream is also used to
determine the correct air fuel ratio. As the oxygen
content changes at the downstream the PCM calculates
how much air fuel ratio change is required. The
PCM then looks at the upstream oxygen sensor voltage
and changes fuel delivery until the upstream
sensor voltage changes enough to correct the downstream
sensor voltage (oxygen content).
The downstream oxygen sensors also provide an
input to determine mini-catalyst efficiency.
My point in posting this is that some people will tell you that the downstream sensors are only there to check if the cat is working... but I tend to believe what is written in the Factory Service Manual. PCM technology improves all the time. Believe it.
Mike your are confused...there are no sensors after the big cat on a 2001. Read it again. it refers to the upstream sensors, but does not call the downstream sensors , upstream or vice versa. It explains how the pcm uses both up and down to adjust fuel ratio.There are errors in that text, in that they refer to the first 2 inline sensors as downstream one minute and then call them upstream in the later description. The first 2 sensors, let's call them "upstream" between the large cats and the mini cats, they are the ones the computer uses for fuel trim adjustment. The down stream sensors, located after the big cats, down stream of both cats is used to measure Cat efficiency, as I said before. From that FSM detail you just posted, it seems that the newer OBD-II rigs do have the computer using the last two O2 sensors not just for EPA clean air testing, but to fine tune the fuel rate if the engine is too rich or two lean based on the final O2 sensor data to get the final exhaust after the large cats into EPA complaince, and perhaps to confirm that the first 2 sensors are working, using a more complex algorithm than older rigs. The O2 concentration does change from the inlet to the large cats to the exit of the large cats. So testing the final O2 sensors should show them running leaner than the first two
Mike your are confused...there are no sensors after the big cat on a 2001. Read it again. it refers to the upstream sensors, but does not call the downstream sensors , upstream or vice versa. It explains how the pcm uses both up and down to adjust fuel ratio.