Injuneer

It's probably running so badly that any issues with the motor mounts, tranny mount, torque arm mount, u-joints, etc. may be emphasizing the engine shake. The data log only shows how the engine is running. “Shake”, or “wasn't all there”, or “wobble” are difficult to define without actually feeling it, and sensing which part of the car the symptom is coming from. These things need to be physically examined to look for damage. Hard to help without actually feeling what you are feeling. Any chance a wheel is loose or bent or lost the balance weights? Maybe one of those bunch of suspension mods broke or loosened up. Can the shake be felt in the steering wheel? …..at the shift lever?

Prospect62

Both. But only under power.

At idle, if you goose the throttle it doesn’t feel as responsive. Kinda lazy if that makes sense. Before, any throttle input was met with an instant, smooth response. Now…it’s “meh, ok”.

Out on the road, it’s not 100% power wise. Shifting through the gears it runs fine, in that I don’t ever fear it’s going to stall. But it’s not 100%. Luckily I have about 100 miles of seat time in this car to know how it “should” feel.

In 6th gear, at or around 2000 RPM and 40-60 MPH, if you lay into it, it will shake so violently I’m genuinely afraid something in the driveline will break if I stay in it. Shift it into 4th and off she goes up past 4000 rpm and beyond pulling hard but not like it used to. No high-RPM miss or skip detected and power seems closer to normal when she’s screaming like that.

Coasting at any speed, no vibes. Cruising at a sweet spot (say 3500 rpm in 4th gear at 50-60 MPH) it feels normal.

It’s an odd thing and what’s so odd is that it just came on suddenly one day. Like I’ve said before, I’ve always suspected the car was running rich but it never ran poorly at all. Just extended crank times and rich exhaust.

shoebox

How does the spark look? Could be a weak coil.

Prospect62

The coil is a year old, it’s an MSD installed by the previous owner. I haven’t tested spark, I’m making an assumption that the coil is ok but who knows. I have a replacement ignition control module on order though, just in case. If the FPR doesn’t rectify the issue I’ll start getting into spark, I guess.

Injuneer

Your data log does not indicate significant misfires.

A misfire dumps unburned fuel and unused air into the exhaust. The O2 sensor can only “see” oxygen. As a result, the O2 sensor picks up the unused air, see the increased oxygen portion, tells the PCM “lean”, and the PCM starts INCREASING the fuel flow, dumping in extra fuel the engine doesn’t need. That means the LTFT’s would rise above 128. But your LTFT’s have dropped like rocks to the lowest value that stock programming (and most aftermarket programming) permits = 108, and then it's using the STFT’s to pull out even more fuel. The problem exists on both banks of the engine, but slightly worse on the driver side.

If you had a single cylinder misfiring, it would be hidden as far as the data log goes by the fuel problem.

You do have continuous periods of knock retard. A small amount in most cases, but in a healthy engine, properly tuned, knock retard should be “0”. You also have excursions of up to 10° of knock retard. That will cause you to sense a loss of power. I need to check to see if the extreme knock retard corresponds with you description of giving it throttle at 2,000 RPM. Generally not a good thing to do because it raises cylinder pressure and temperature to the point it will cause knock. No point in using 6th gear to accelerate, unless you ran into redline in 5th gear, and that's unlikely. Great for cruising the freeway at 70 MPH, but if you want to accelerate, drop it down to a lower gear before you hammer it.

The great unknowns at this point seem to be related to fuel. You have an unknown tune, maybe different injectors than it’s tuned for, a seriously failed FPR. The “shake” may be totally unrelated to the problems picked up in the data log. But I wouldn’t continue to drive the car until you at least replace the FPR and verify the correct pressures. In the meantime, if you can, start looking at things like the tranny mount, u-joints, etc., any of the things mentioned above.

Prospect62

Thank you, Injuneer. Your insights have been priceless for a guy brand new to this platform and engine.

Hopefully the new FPR will do the trick. Meantime, I’ll crawl under and check mounts and joints out.

Prospect62

The new FPR cured the extended crank time issue. The “shake” is much improved but still somewhat perceptible under certain conditions. I sincerely cannot remember now if it always had a little of the shake. Either way, it’s improved. Power seems to have been restored.

I think my driver side motor mount is failing based on a quick inspection, but really I’m just being picky. Overall the FPR improved things…a lot.

I haven’t taken pressure readings and my laptop took a crap (I think I got a virus) so no data logs today. I’ll follow up.

Thanks Injuneer for your sage insights.

Prospect62

Got the computer running and took a nice long drive, logging the whole way.

There's definitely a shake or vibration that seems more pronounced than when I first bought the car, yet still WAY better than it was over the last week or so. It's only noticable when under power, seems to fade between 3000-5000 RPM. If you put the car in neutral and coast at any speed, the shake/vibration goes completely away. It's mainly felt in the shifter ****. A passenger probably wouldn't even feel it. I saw a small crack in the rubber on the driver side motor mount, I'm betting dollars to donuts that's what I'm dealing with. The rough running from the bad FPR bust have just really exacerbated the issue.

I don't feel it's a u-joint (though I have not checked that yet). I suppose it could be a trans mount and I really hope it is, because I'll sell this car before I do motor mounts. Did them last year on a K5 Blazer and swore I'd never do it again. These look even stupider based on the complete lack of room to work.

Anyway, feel free to peek at my newest datalog Injuneer. Overall, the car starts and runs and drives worlds better than it ever has and chances are I'll forget about the shake/vibe unless it gets worse, in which case the car goes. Thanks everyone for the help!

Injuneer

Did you check the fuel pressure after installing the new FPR? Still a problem. Quick look at the log, focusing on the end, where it's idling. The Bank 1 LTFT in the idle cell (16) is still bottomed out at 108. But it's no longer using the STFT to pull out additional fuel. Bank 2 appears better at 132. Still that continuous small amount of knock retard at idle. Could be something mechanical.... e.g. broken motor mount, exhaust hitting something, etc.. When you get aggressive on the throttle, more knock retard, up to 7 degrees.

It's not a stock tune.... target idle speed fully warmed up is 950 RPM. Looks like a bit more ignition timing at idle.... high 20's where stock is usually around 20-deg. First fan came on at 162-deg, second at 176-deg. seems a bit too low. Typically you want the fans to run after the t'stat is 100% open, and that would be ~180-deg running a 160-deg t'stat.

Again, just a quick look.... this is a HUGE file, (1.2 million cells), probably one of the largest I've ever seen. Might wnat to read my guidelines for data logging:

https://www.camaroz28.com/forums/com...-guide-886891/

Actually, I'm violating my own policy of not reviewing these logs any more.

Prospect62

I appreciate you looking at the log, I know it's a big file. Honestly I had no idea you had guidelines and I understand you're volunteering your time so please don't feel obligated - you've already helped enough.

No, I have not checked fuel pressure readings with the new FPR yet. I noticed that fuel trim of 108 at idle towards the middle and end of the ride and I remembered how you pointed that out before. That was after a long hard drive on a hot day and to be honest I was so happy to see the marked improvement in the fuel trims for the other 95% of the log that I kind of glanced over that brief period of 108's. What's odd is that Bank 1 LTFT being at 128 or so for the first 20 minutes of the ride then departing from that reading and going back lower for most of the rest of the ride.

The knock retard at idle is being cause by something hitting something under there at idle, I can physically hear it and the car has always done it since I've owned it. But I also noticed that the knock retard was ALSO significantly reduced over the original runs. Yes, I need to see what's hitting what.

As you can see, the car runs in the 180's, climbing up to 198 after a run into the triple digits. I have no idea what T-stat is in it but yes, it appears the tune was changed to turn on the fans sooner.

The last question I'll ask is what would cause one bank to be at that 108 fuel trim (even if it was briefly) while the other one seems normal? What would cause it to be normal for 20 minutes then going wonky after the car got good and heat soaked? The car has a stock throttle body on it with an airfoil. I did remove a BBK 52mm that came on the car that was sticking which I didn't feel like messing with. Could there be an injector issue? Oxygen sensor?

Craymaro

Did you ever figure out the shaking under load issue? I’m having fuel issues like you but I’m lean not rich. I just ordered a fuel pump which I’ll install soon. But my cars doing that terrible shaking underneath the car around 2k-3.5k rpms in 5th and 6th gear. It drives fairly normal besides some occasional choppy throttle response.

Injuneer

Hasn’t returned to this site in almost 2 months. Guess his problem went away……..