It's running rich by the long term fuel trims. Could explain the stink. And running rich will have an impact on the cats.
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
What all sensors on a 5.3 effect the way it runs? (Narrowed it down)
- Thread starter shady
- Start date
Both banks have negative fuel trim numbers. So from that perspective it's not isolated to one side.
It really comes out if you graph what the o2 sensors are doing over time. Like it was mentioned before the front sensors b1s1 and b2s1 will have a wave form that has a wide swing in voltage. They will switch high and low pretty quickly when working correctly. They don't have to match, but at least be similar. If one sensor is lagging or slow it take longer for the wavelength gets spread out on the graph.
The post cat o2 sensors should switch up and down too but just not have as wide difference in voltage, as in a shorter waveform than the front sensors.
If you can graph two values at once do both bank 1 sensors and then again on bank 2. Seeing them together should show the difference in the wave forms. Typically if the pre and post cat sensors read a similar waveform the cat itself is not changing the state of the exhaust. Meaning it's not working. It's not plugged since in that example the rear o2 sensors are switching.
You can compare both front sensors on the same graph to see if one is switching slower than the other too.
It looks like your tool should give you good data on it at least.
I didn't know, has it had the intake manifold resealed? Low vacuum could possibly be a leaky intake, correct? The MAP sensor would tell the ECM to give it more fuel.
I say this as I have heard of this being a problem. Even had one parts truck that I could hear the whistle around the intake.
I say this as I have heard of this being a problem. Even had one parts truck that I could hear the whistle around the intake.
The one that I parted out had 171K on it. I snugged the bolts to the low side of the spec, and changed the sound, didn't fix it though.
8 intake manifold bolts, why would that leak 
, fickin bean counters.
, fickin bean counters.
Any intake leak allowing un-metered air at idle will cause the LTFT to go positive to compensate. Likewise, if it starts misfiring or there is an exhaust leak, that will also bring in extra oxygen and read lean. Negative values imply the airflow metering is wrong, there is an air restriction or the literal interpretation of too much fuel.
Has the MAF been cleaned? There is no oiled air filter in play here, right? I would also verify that the PCV hose is actually drawing air.
But first let me ask - has anything been reset since you cleaned the throttle body? Or has it been driven a lot? The LTFT takes a while to change and a bunch of criteria have to be met before they can change at all - like engine temp, closed loop, etc.
Has the MAF been cleaned? There is no oiled air filter in play here, right? I would also verify that the PCV hose is actually drawing air.
But first let me ask - has anything been reset since you cleaned the throttle body? Or has it been driven a lot? The LTFT takes a while to change and a bunch of criteria have to be met before they can change at all - like engine temp, closed loop, etc.
Also want to mention that LTFT within +/-10% is usually considered OK. It's great to have them closer, especially for the times the engine is running open loop or in PE (which on a stock truck engine is virtually never), but with low STFT numbers, the engine has it figured out.
You're also going to see variation seasonally, as they mess with the ethanol content in gas - unless it's a FFV, which has a sensor to compensate.
You're also going to see variation seasonally, as they mess with the ethanol content in gas - unless it's a FFV, which has a sensor to compensate.
After changing the throttle body he's driven it probably at least 1000 mi or more.
At the point when i took them readings it was running smooth.
If he hits a decent bump it all goes to hell. Until he shuts it off.. let's it sit a minute, then starts it back up.
That's why I thought cat. Because the cat makes a sound like light pieces of potato chip bouncing around in there.
But I need it to be in that run bad mode to hook the scanner back up and check it then. Hard to do with him living his own life across town.
I need a free day we both have off to have him drive me around to make it do it. Or,
Once I fix the starter in my burb I'll be able to trade him for a few days.
At the point when i took them readings it was running smooth.
If he hits a decent bump it all goes to hell. Until he shuts it off.. let's it sit a minute, then starts it back up.
That's why I thought cat. Because the cat makes a sound like light pieces of potato chip bouncing around in there.
But I need it to be in that run bad mode to hook the scanner back up and check it then. Hard to do with him living his own life across town.
I need a free day we both have off to have him drive me around to make it do it. Or,
Once I fix the starter in my burb I'll be able to trade him for a few days.
Bad smell, rattling cat. Seems like you already know at least part of the problem. Know anybody with one of those cheap boroscope cams that could be fed in an O2 sensor hole? I can't remember where the joints are in the system to know if the whole Y-pipe can be unbolted, but I will say I've head great luck taking the exhaust apart on these, even ones that have been in salt their whole life. Seeing graphs of the O2s may still help, but if the catalyst material is sometimes not blocking the path, it's possible the readings would be fairly normal then.
We were going to pull out the pipe and shake it out. If prices fall out like we think they will, then we're going to knock the rest out of the cats or eliminate them.
Can't afford to replace em at the moment. Or foreseeable near future.
Had it all ready to go the other night and realized I didn't have welder gas if we needed it. So it got postponed
Can't afford to replace em at the moment. Or foreseeable near future.
Had it all ready to go the other night and realized I didn't have welder gas if we needed it. So it got postponed
Should be able to separate the y pipe from the muffler pipe.
I do it all the time, non rusty California trucks thou.
I do it all the time, non rusty California trucks thou.
All the bolts on his are in really good clean shape. Shouldn't be a hard job.
Both cats have bends infront and behind them. If I knock the rest out I'll probably have to cut on one end of each to get something in there. Then weld em back together
Both cats have bends infront and behind them. If I knock the rest out I'll probably have to cut on one end of each to get something in there. Then weld em back together
If you cut out the cats then you definitely will end up with a check engine light for catalyst efficiency unless you have or know some one who has HP Tuners to turn off the codes for the rear O2s.
AFAIK, O2 emulators still work on these engines. Someone else may have experience. Will be stinky. A pick-n-pull may sell this whole assembly at a price reasonable enough to avoid buying the roll of stainless and pair of emulators. Again, no experience implied.
