fbody_brian

Guess I'll post this here, as I don't think it's really LT1 specific. I've searched a lot and have found other people with the same issue, but never any solutions.

I get a lot of fluctuations in my rpm at WOT. the logs look really jerky. Like it will go up a few hundred rpm and then drop back down a little then repeat.
Strange thing is I don't feel it at all and the car seems to run strong for what's done to it.

I thought that it was possibly fuel knock as my knock counts were climbing last time I logged at the track when it happened. I removed some timing and installed a 160 stat and got rid of the knock counts. Yesterday I got 0 knock counts but the log is super rough, with the rpms fluctuating the whole WOT run through 2nd and 3rd gears

Things I've done so far.
Changed the plugs, checked fuel pressure, cylinder drop test, tested injectors, logged AFR with wideband.

Haven't done a compression test, it's on the list.

Things that are questionable.
Transmission does strange things sometimes, not wanting to shift from second at moderate part throttle, ALWAYS shifts at full throttle. Also sometimes it will pulsate on decel, like it's grabbing and slipping, but not always. Has never had engine braking when when in manual 1-2-3. Not sure about the torque converter, went with a dacco reman unit because of tight funds.

Rear end, not sure about the condition, has some seeping at the axle tubes, sometimes get a slight clunk when accelerating from a very slow coast. It came from a 02 manual car. don't know the history. I'm not easy on it.

Engine was freshened up by the previous owner. New rings and bearings. Had about 1k miles on it when I purchased.
Found a lot of stuff wrong with the car that was not disclosed by the PO, so everything is questionable.

Anyone know what to look at next?
seen this before?
I'm at a loss here.

Thanks

fbody_brian

Why'd this get moved???
Was hoping to get a wider audience than just people that visit the lt1 section, as this is not a problem specific to the lt1:

https://ls1tech.com/forums/automatic...ation-wot.html
https://ls1tech.com/forums/forced-in...ation-wot.html

steveo_

the stock tach is filtered, so a high rpm misfire might not show up but it might in the logs.

can i see a log?

fbody_brian

Sure

rename the .txt to .eedata

fbody_brian

Here are the files, csv and eedata(txt)
I have just the wot section if it's easier.




Edit:
if you're opening this in $EEhack, my wideband is configured:
Low point 9.00:1
High point 5.000v 19.00:1

it seems to export the WB data to the csv, so all good there

myltwon

iTrader: (1)

How's the vacuum?

fbody_brian

Between 33 and 38 kpa at idle
Between 95 and 101 kpa at WOT, Baro is at 103 kpa

steveo_

log looks like maybe a heavy load misfire or something like that?

your AFR starts pushing towards 14:1 too, which could be further evidence of some extra air in the exhaust from a misfire.

bad coil or plug wires would be my first bet.

fbody_brian

I'll be checking the plug wires and inspecting the plugs this weekend. I also had someone else suggest a misfire, or valve issue. I can hear a lifter sometimes, so it may be that. I was hoping to wait to pull the intake until I put a cam in it, but I may have to do it sooner.

It's just so strange that I don't feel that. I see it in the logs looking like it would be obvious when I'm driving, but it's not.

Thanks for the suggestions

steveo_

a noisy lifter wont cause that kind of thing, but an arcing plug wire can sound like a lifter tick.

the variation in RPM is fairly small in the scheme of things, i doubt you'd feel it.

this entire thing might be a non-problem, but im used to seeing WOT rpm being pretty smooth compared to that..