JTS97Z28

iTrader: (4)

I did a search and actually came across a lot of threads regarding something similar but didnt really come up with anything. I dont even know if its a problem but on my recently acquired 08 TL-S 6mt it seems like mainly in 3rd gear the car doesnt accelerate 100% smoothly. Just as a note this has nothing to do with enagaging the clutch, or the 3rd gear shifting issue because that all works fine. Im talking about while in gear with foot off clutch pedal. It seems that during normal acceleration that you can feel the car surge very lightly. This is not excessive infact my wife doesnt even notice what im talking about but I kind of do. I dont think I have felt it in any other gear mainly around 3rd gear. I read someone mention something about the EGR valve. No check engine light or anything.

Thanks for any ideas.

James

JTS97Z28

iTrader: (4)

Wellp for what its worth for the heck of it I tried that ECU "reset" procedure and removed and cleaned the EGR valve. On initial drive the car does seem smoother so we will see how that pans out. Still looking for additional info if anyone has it.

Thanks,
James

justnspace

iTrader: (1)

James, have you checked out the "slave cylinder check valve mod"?

JTS97Z28

iTrader: (4)

I have not any chance you can give me more info on that? And does it have to do with what im explaining? EDIT: I did a search and read about the check valve mod. Sounds interesting but my issue happens even well after you shifted. During accelerating from a light for example while accelerating in 2nd and 3rd gear you feel the car surging a bit.

I drove the car a little today and the shuddering was still there I noticed it in 2nd and 3rd gear. Best way to explain is during a constant acceleration (not during any shifting or anything) you just feel the cars power band interrupted I guess you can say (almost like how you can sometimes feel a slight hickup when your a/c compressor engages and disengages. Its not a shaking vibration but more of a slight surge. Its not bad by any means but I can notice it.
Any additional info would be appreciated.

Thanks,
James

speedytypes

Ive got the same car as you and it does the same thing, at times it feels like its got more power then usual as im just gradually going through 2nd and third gear. I wish it were that powerful all the time. Its by no means slow now but at times it just seems to have extra power for a split second or so. Maybe its got to do with the drive by wire?

I hate cars

Would you say it does it under load and at lower rpms? Will it do it at all when cold? If not you might start with plugs/coils.

What happens if you floor it at 2000 rpms in 3rd?

I assume you're running premium and its not the ECU rapidly pulling and putting in timing.

JTS97Z28

iTrader: (4)

As far as I know it does it no matter what engine temp. I have noticed it well after the motor should have been at full operating temp so its not just a cold thing. I guess you can say it does it under load as I only have noticed it during normal acceleration and while going through 2nd and 3rd gear. I will do more diagnosing today and try different situations. I read other threads where a guy said he used cruise control to accelerate and it was perfectly smooth.

I will try flooring it at 2000rpm in 2nd, and I will also try something similar in 3rd gear.

As far as fuel yes I only use premium however I did just get the car not long ago and the dealership I bought it from filled the tank for me...I can only imagine they would use the cheap shit, and if they didnt I would be VERY surprised. That tank is long gone though as it was a 400 mile trip home when I bought the car and have used nothing but premium obviously since I got it (but have yet to go through one entire tank since I got it home). I would say though that your explanation of rapidly pulling timing and putting in timing is also another good explanation of how acceleration feels.

On other threads I have researched some common things people mentioned were APP sensor, TPS, EGR valve...stuff like that. THe car is still under factory warranty so worst case I can bring it in, but its one of those things that either the dealer is going to say is normal, or maybe I would be surprised and they can fix it.

Thanks for any input.

James

justnspace

iTrader: (1)

if it were the APP sensor, the car would go into limp mode and you would not accelerate past a certain RPM and speed.
I'm ruling that one out.

JTS97Z28

iTrader: (4)

I drove the car today and it does it with VSC on or off (read other threads where guys said to try that). Engine temp for sure makes no difference. If I floor the car in 3rd gear at 2K rpms's you can feel the surging. Does the same in 2nd gear as well and seems to smooth out above 4Krpm's. No check engine light car idles and runs perfectly otherwise and fuel economy has been very good so far. 29mpg highway 23 around town (according to MID).

James

SouthernBoy

Just for kicks, pickup a can of Sea Foam Motor Treatment and follow the directions.

JTS97Z28

iTrader: (4)

Ehhh I would but the only thing that keeps me away from that stuff is that I think it can possibly foul up everything from your spark plugs to your 02 sensors. What I am going to try though just for the heck of it is when my tank gets low I will throw in a bottle of Techron fuel treatment. Im normally not the kind of guy who likes to use fuel treatments or other additives, but on the other forum I visit Corvetteforum.com the guys over there swear by the stuff.

Thanks,
James

JTS97Z28

iTrader: (4)

no other ideas guys? ;-l

speedytypes

Ive done the seafoam a couple months ago, so i doubt that will help. Car did it today as i was flooring it at 2.5k-4k rpm.

JTS97Z28

iTrader: (4)

Alright well I appreciate any help guys but since im not getting many ideas from the forums or searching I guess I have to bring it in. Appointment is set for 9:30am thursday and set up for a tech to go for a ride with me. Hopefully we get somewhere and I can get it fix. Its just super annoying to be driving a car that doesnt accelerate smoothly. Anymore opinions are appreciated otherwise I will just post back when I hear from the dealer.

James

MarcDavidoff

Bringing back another of your old posts
Seems I have some of the similar little nuisances that you have had. You ever figure this issue out? I notice the same as you have described. Mainly 3rd gear lower rpm if you take off pretty spirited it almost seems to bog some then as rpms increase to say closer to 4k it smooths out and takes off faster as if it overcame a small dead spot in the throttle..