On my 2004 TL (6MT), there is subtle surging in cruise at a range of speeds, incl highway speeds, similar to if the a/c kicks on and off, or wind gusts are hitting the car. It is less with the cruise control on. Premium gas used. At WOT, there is no issue, nothing at idle. Mileage is the same. Been noticing past 1 year, car close to 100k. The closest thing I could find to this in the archives is an EGR valve issue. Anyone else have this, and found a fix?

 

Actually, further research in the archives seems to relate to the APP sensor. May try and pull a code on this.

 

I have been trying to hunt down a similar issue with
my 08 Type S 6mt. Your description is the same except my car is perfect smooth at cruise. I only feel the surging during acceleration. Feels same as you describe like a/c clicking on and off but several times during accelerating mainly felt in 2nd and 3rd gear. Full throttle is perfect, fuel economy is excellent, and no check engine light. Car has been to the dealership multiple times with no luck. I have also diagnosed the shit out of the car myself also with no luck. I tried plugs, coils, IAT sensor, EGR valve, APP sensor, tried driving with 02 sensors unplugged, did clutch tests. Absolutely none of these changed my surging acceleration. Dealer also installed the latest ECU software which didn't do anything either. I filled the car with race fuel to see if it was detonation or knock retard. Didn't help.
I test drove an 07 type s 6mt yesterday and it was perfectly smooth during acceleration so I know for sure something goofy is going on with my car.
Only thing I can think of now are fuel injector, fuel pump, defective ECU, or a bad catalytic converter. I'm out of ideas. The car is going back to the dealer one last time for my appointment tomorrow morning.
I will keep you posted.

James

 

Well, problem fixed with replacement of the APP sensor. Thanks to some threads with pics on this this forum, took just 20 min. No more surging holding the throttle in cruise, any speed.

 

Nice job glad you fixed it. Wish I could figure out the surging during normal acceleration issue with my 08 TL-S 6mt. Its weird your issue was during cruise where as mine is perfectly smooth at cruise, and mine is during acceleration. APP sensor is not the issue with my car. Wish it were that easy. Anyway, glad you got it figured out.

James