BOGGING BADLY! - SOLVED

[j91z28d1]

with that much retard you might see some misfires too.

huh, if you can get it to keep doing it, what do the o2 sensors show and fuel trims?

maybe make it do it, then turn it off before it clears up, coast to a parking lot and pull a plug? see if it's fluffy back or super clean? might help know if it's really rich or lean to compare to scanner data.


I once had a evap full of fuel, and when the solenoid opened to return the Vapor, it flooded the engine. sometimes stalled out, others it just ran really bad. but the o2 sensor voltage did go dead rich.

 

[mikez71]

Thanks all. Here is a screenshot of datalog. LT and ST fuel trims seem to fluctuate from -12% to +3%.
Forgot I removed the O2 sensor polling, will do another log soon.. knock retard -13.7 degrees on the cursor.
Not sure if false knock, or something bogging the engine down and it's actual knock.

 

[Doubeleive]

Thanks all. Here is a screenshot of datalog. LT and ST fuel trims seem to fluctuate from -12% to +3%.
Forgot I removed the O2 sensor polling, will do another log soon.. knock retard -13.7 degrees on the cursor.
Not sure if false knock, or something bogging the engine down and it's actual knock.

View attachment 432569

this is mostly foreign to me but am i seeing TPS is reading 93 % at 2000rpm??
*edit I guess that's what it's supposed to be but doesn't seem right

 

[mikez71]

Yep, it's bogging so it's accelerating slow. Hard to imagine bad O2's can make it run so bad. Idle's and revs fine.
Hope I didn't wreck the trans somehow by tweaking the settings...

Pulled out of driveway, accelerated down street, first stop sign major bog. Bog it at 40% throttle, push to 90% throttle. still bog.
O2's seem alright, fluctuate normally. no misfires. engine load at idle 20%, with A/C on 23%.

 

[Fless]

Thanks for the help! Still runs like poop.

8.5 g/sec at hot idle. Driving it spikes up to 130 g/sec, i never went past 71% throttle that run.
Knock retard upto 13.5 degrees.. whenever over 45g/sec in 1st or second gear..
Just doesn't feel right like there is an ebrake on, or worse.

Looking at previous logs, the MAF readings seem to be in similar range. WOT previously had 220g/sec, idle ~6.5 g/sec.

Will take a look at the MAF and plumbing and check for misfires once more..

I'd say that one problem might be that the MAF seems to be over-reporting. How long since it's been cleaned? At hot idle the reading should be closer to the engine displacement (5.3) in g/s. 8.5 is quite a difference.

 

[mikez71]

Will do! (Never cleaned)

While my MAF readings look consistent from ane acceleration to another, with only some accelerations knocking. This video around 11:00 minute marks shows adjusting the knock sensitivity based on MAF and RPM. As you say if my readings are so off, it could be moving into another area of the map.

My logs also look a lot like this video

in which he claims it was a bad motor mount! (Did I **** up installing motor mounts?)

Something special about cylinder 4.. ?? Anyhow will clean MAF and get back on that..

 

[mikez71]

Cleaned MAF, no change! Starting to wonder if my cat's are clogged.. truck really struggles to pull from a stop. Smooth but plugged up feeling.

Another log showing O2 fluctuations and what looks like 6 knock retards ending in 5 knock retard events.

 

[Foggy]

Your fuel trims are well within acceptable ranges...
I think you've found your issue.. Cats are bad.
Classic symptoms of cats that have come apart and clogged
up the exhaust is my guess too

 

[B-train]

I would concur with the bad cats idea. After reading through all of this I remember my 2001 Impala with the 3.8L. All of a sudden after it was hot, I couldn't accelerate, would have engine knock, etc. Very much the same acenario you are experiencing. Ended up being a recall by GM for the catalyst. But, I was such a road warrior that I blew right past that warranty period and just knocked out the inside and put it back in. Gained 3 mpg on the freeway afterwards. Heck yeah!

 

[j91z28d1]

you're definitely in a part of the map that isn't normally at, that's why your at - 10 deg timing and somehow it's retarding 12 more that's kinda crazy.

these days guys look at airmas/g cyl instead of map vs rpm for timing and retard. it's a rabbit hole to go down. not that it makes any difference in this case.


I've never actually had clogged cats. if that's it, I learned something today haha. cause I don't see much wrong in that screen cap that would cause all this.