Low RPM <1600 bucking, any gear

[Ravs]

Hi everyone!

This is my first post and I'm happy to be a part of the community.

English is not my native language so please forgive me.

About year and a half ago I've bought a 2010 Camaro SS with a LS3 engine, so it is equipped with manual transmission. A bit of the my ownership history: the car was already modified with long tube headers, ROTO-FAB cold air intake and a tune (probably) when I bought it. Since day one I have it would be running rich on cold starts (you could smell the gasoline odour, but no anymore when engine warmed up). So after a week or two I took it to reputable repair shop in my part of the country (Poland) to fix little gremlins it had (trans input shaft bearing and the drive shaft had to be replaced) plus I've asked to clean/oil the air filter. Since I've collected the car it has developed a strange bucking, that only appears off throttle (or with super minimal throttle) below more-or-less 1600 RPM, in any gear, you can see it in the video here: https://www.youtube.com/shorts/5dTGUvTxRUQ - please keep in mind the video was recorded while driving in 2nd gear and speedo is set to kilometers per hour. With slightly more throttle input it goes away and the car flies up to the red-line. Pushing the clutch in obviously cancels the bucking away.

Couple weeks later unfortunately a valve has dropped and kissed the piston. The engine was rebuild alongside BTR Stage 2 cam with all supporting mods (pushrods, valve springs, timing chain, timing gears, etc...), new plugs, plug cables and bunch of other things and a new custom tune of course. And guess what? The below 1600 RPM still remains and drives me crazy plus the smell of gasoline still persists on cold starts. Due to the modifications I cannot de-tune to stock map of course to check if it helps anyhow. I have a feeling it is ignition related (and not driveline related because it seems to just start bucking below 1600 RPM regardles of actual RPM - it "feels" the same at 1200 RPM as well as at 1500 RPM), the "only" old pre-build parts are ignition coils, injectors, MAF sensor, fuel filter/pump... Any ideas where to start looking at things?

TL;DR - the car bucks forward/backward off throttle during engine breaking/deceleration (or VERY slight throttle) - under 1600 RPM, in any gear. Runs fine with a bit more throttle or under WOT.

[1JEWLDSSRS]

Hello there, welcome! For starters on the fuel smell on cold starts, that is normal for a car with long tube headers that don't have cats, mine is like that, as it warms up it does go away a bit.You didn't say if the exhaust had HFC's, or no cats at all. As for the "bucking" issue you have at or below 1600 rpm, that is normal for a manual car with a cam such as what you have, you just need to go a lower gear when driving slow, or when cruising drop down a gear so the rpms will be higher past the point where it lugs down the engine. Hope this helps..

[SS_Dave]

You need a better tune done.

[1JEWLDSSRS]

Originally Posted by SS_Dave

You need a better tune done.

Yes, forgot to mention that as well. The tuning does mean a lot for good driveability.

[Ravs]

Thank you for your answers guys. I'll ask my tuner to check it once again (he'd need to look for the issue for the 5th already)...

On the other hand as I said, it was bucking exactly like this BEFORE the engine re-build and installing the cam. It started doing this after it was in the repair shop to replace input shaft bearing, drive shaft and the air filter was cleaned and re-oiled. Could the MAF be dirty and/or fouled in filter oil?

I really don't think the tune is the issue. It had/has two different tunes sourced from two independent tuners and it behave exactly the same on both of them. Plus, after rebuild I had to buy a new ECM, because the old one was locked and couldn't be tuned. Still I will ask for another revision of the current tune...

[SS_Dave]

I just looked at the video. Honestly, I'd say a lot of that is your driving style. You're lugging it. Stick doesn't like that low of RPM. Lower gears and wind them out as Jewel mentioned.

[MSgt O]

like Dave said...your RPMs are too low for that gear. I have same manual/LS3, same cam, headers etc...same fuel smell when cold and bucks if youre not winding out the RPM in lower gears. Not the car, but the driver Youre at like 18mph in second!! And welcome all the way from Poland! Must be great racing around in that car over there!!

[Ravs]

You might be right, I don't disagree. Maybe I just need to adjust, because over 15 years of owning multiple performance-kinda oriented cars (I've owned 2004 Mustang GT, 2009 WRX STI, 2011 Mustang GT, Focus RS MK3 and now this Camaro, all equiped with manual trans) none of them behaved like that. I really didn't think ~1500 RPM would lead to engine lugging... But is it really lugging? Apply a bit more throttle and it goes without any hesitation. At the end of the video I've allowed RPM to drop a lot, yes, I did it on purpose. But around 00:15 it started to buck when RPM dropped to more or less 1500. Is it really that low? Again, it does it in EVERY gear around that RPM level (with higher speed for higher gears of course).

I know you guys are trying to help and I really appreciate that!

[MSgt O]

If it stops raining Ill take my car out and do exactly what you did and the car will do exactly the same. Remember you have a bigger cam in it, so thats where the rpm and cam cause the lugging regardless of what gear

[Ravs]

Originally Posted by MSgt O

If it stops raining Ill take my car out and do exactly what you did and the car will do exactly the same. Remember you have a bigger cam in it, so thats where the rpm and cam cause the lugging regardless of what gear

Thank you very much, please let me know! Although as I said in the initial post, the car did that BEFORE the cam was installed.

[SS_Dave]

Originally Posted by Ravs

You might be right, I don't disagree. Maybe I just need to adjust, because over 15 years of owning multiple performance-kinda oriented cars (I've owned 2004 Mustang GT, 2009 WRX STI, 2011 Mustang GT, Focus RS MK3 and now this Camaro, all equiped with manual trans) none of them behaved like that. I really didn't think ~1500 RPM would lead to engine lugging... But is it really lugging? Apply a bit more throttle and it goes without any hesitation. At the end of the video I've allowed RPM to drop a lot, yes, I did it on purpose. But around 00:15 it started to buck when RPM dropped to more or less 1500. Is it really that low? Again, it does it in EVERY gear around that RPM level (with higher speed for higher gears of course).

I know you guys are trying to help and I really appreciate that!

Tell ya what. I'll putt around in mine later today and see how it acts. In my case, though, I've got a stock motor with headers, intake, tune, and 3.91 gears.

[Ravs]

Originally Posted by SS_Dave

Tell ya what. I'll putt around in mine later today and see how it acts. In my case, though, I've got a stock motor with headers, intake, tune, and 3.91 gears.

Thanks! Looking forward to the results!

[1JEWLDSSRS]

Originally Posted by MSgt O

like Dave said...your RPMs are too low for that gear. I have same manual/LS3, same cam, headers etc...same fuel smell when cold and bucks if youre not winding out the RPM in lower gears. Not the car, but the driver Youre at like 18mph in second!! And welcome all the way from Poland! Must be great racing around in that car over there!!

This^^^ even though you owned "other" cars with a manual trans, and they didn't act like that, every car has a different personality, and our Camaros have really different ones. So yeah, you are driving in the incorrect gear for the rpm's you are turning, especially now that you have a bigger cam. Next time you go out and it does that, at what ever speed you are going, slow, cruising, just drop down a gear and it should all go away. I just believe you need to adjust your driving habits with the car. And also dropping down a gear your acceleration will also get better when you push the throttle...

[SS_Dave]

Originally Posted by Ravs

Thanks! Looking forward to the results!

Ok. So I tried it. Yes, I can get that low and be mostly smooth, but it's a pain. Super senstive in moving the accelerator at all. So while I think your converter may need to be sized differently to be best, it just doesn't appreciate being driven at such low RPM.