So I have this problem that happens only on the highway & it doesnt always happen.

Ill be doing bout 55 on the highway and when I want to move a lil faster I accelrate just a bit and the car just doesnt want to move. The car just shakes, hesitates. I ease off the gas..wait 3 or 4 seconds later and accelerate again and there is no problem. I noticed while the car was shaking that all gauges seemed to read ok and no check engine light. Its sooo annoying. When the car shakes like that it freaks me out. But this problem isnt consistent. it doesnt always occur.

any ideas?

 

My guess would be EGR since its only happening on the highway.

 

Just got a new EGR year ago.

 

Id suspect a burnt spark plug wire or 2. Simply inspecting them sometimes doesnt work unless its really obvious. Instead go out in the dark and with the motor running just pop the hood to see if any of the wires are arching or flashing. A small glow around the inside of the boot, around the plug isnt anything to get alarmed about. What you really need to check is any place a wire is laying on something metalic like the valve covers or alternator, header!... ect.

 

Wouldnt the problem be happening all the time if it was a bad plug?

 

You ought to get a scan of it so you can see whats going on.

 

No and I really dont know why either. Way back when I first installed headers I had the same problem(car would violently shake in 6th gear under 2k rpm trying to accelerate) but my wires were brand new and clearly not touching the headers. After a lot of investigating I ended up finding a couple of small cuts in the boots from those stock metal shields I mistakingly reused. I removed the metal shields and patched the cuts with some RTV and the problem went away.

 

Something will show up in the scan even if the check engine light doesnt go on?

 

Scan the car while running and check the knock sensor to see if it's pulling timing. Also check your fuel pressure under load.

 

I have almost your exact same problem with my A4 and 3.23 Gears. I have never solved it either.
The only difference in your description is that it only happens sometimes, could you clarify a bit more. Did you mean it ALWAYS happen at that speed when giving it a little gas? I can replicate it every time i drive in my car. If its not in that speed area and the right RPM then it doesn't do it any more and runs great...

I've almost replaced every darn thing on my car, plugs, wires, coil, block and bottom end, egr, fuel pump, Intake elbow, IAT, Thermostat, cleaned the TB, cleaned the Intake, MAP, fuel filter, Air filter, opti, transmission. Etc etc.



It's STILL there!
I have also freescanned it and it doesnt look anything too noticable. The car runs a bit rich when it happens and the MAP pressure drops almost to BAR pressure.

The plugs/wires solve most peoples low RPM stumbles, coil fixes some HIGH rpm misses, opti fixes everything in between . But what we have is something that only happens around 55-60mph, while crusing on the hwy and giving the car a bit of gas just to accellerate. The pedal moves maybe 20-30% with little or no change in power.

If you ever fix this please let me know

I'm replacing the fuel pressure regulator hopefully this weekend.... I'll cross my fingers again for the 20'th time

 

That doesnt make me feel any better that you replaced lots of parts and still have the problem!! It would be easier to figure out if the problem happened all the time. But it doesnt!!!

 

Well if yours isnt happening always when cruising at 55mph and accellerating lightly, perhaps you dont have the same problem as me then

Check your wires and plugs, look for arching as posted above. Check your fuel pressure, scan the car and look for knock. Theres hope yet!

 

Thanx!!