My 2001 SS A4 Convertible is great, except when I cruise around. Little jerks or hitches every 3-5 seconds mostly felt between 35-70 mph. It doesn't always do it but it is persistent. The tach does not move when the car jerks. Light acceleration is fine. Jerks happen when maintaining speed with or without cruise.
WOT acceleration is fine and the idle bounces occasionally in park, but then can be normal.

Car has 220 heads, 232/232 0.595/595 114 LSA, 95 mm Fast intake and throttle body, 100 mm Lingenfelter MAF, Fast Toys lid, 255 lph Racetronix fuel kit, Ford 42 lb green top injectors, Vigilante 3200 stall, 3.73 gears, NGK Tr6 plugs, Kooks 1 3/4" headers, EFI Live dyno tune

I have replaced numerous things trying to fix it. I had MSD coil packs and 3 different shops said they were the problem and were junk. I liked them, anyway I put the stock coil packs back on and the problem seems slightly worse. I guess it wasn't the MSD's.

I have replaced the plugs, MAF, transmission, torque converter, ring and pinion, limited slip, fuel filter, fuel pump, O2 sensors, and the computer has been retuned by 2 different shops.

No codes.

I drove around with a transmission pressure gauge, with no change in pressure when the jerking occurs.

I have driven with a GM tech tool and a laptop running EFI Live. No misfires were ever detected and race shops along with GM dealerships have been unable to find anything wrong.

It feels like it is going in and out of lockup but the computer says it is staying in lockup when the jerking occurs and the tach does not move.

The car is no longer fun to drive and is driving me crazy.

Any help would be appreciated.

 

Did you do compression and leakdown? Also, how is the idle tuned? I have seen that little hicup before and it happened because the idle tune was open loop but the part throttle was closed loop. It would blip when it made the transition.

-Geoff

 

I have not had a compression leakdown test done. I will have to call my tuner to ask about the idle.

 

Try recording a sample cruise rather than watching it live. Then go thru the file slowly. It could be doing something fast enough that you won't see it live but might see it on a slow perusal.

 

Thats a good idea. My tuner is 3 hours away though, the next time I get up there I will ask for that.

 

More than likely tune related.

Good luck