Harddrive2000

Decided to touch a few things and see if it made any difference. Basically, i cleaned out the air intake system (filter, air box, MAF, IAT, TCM). I also checked the plugs. Turns out the ignition coil for plug 4 was not properly and firmly seated. Cleared the codes and went for another test drive (actually 2 drives). No luck, speed still limited to 85mph. Engine will rev up to 6000, but once i get to 85mph, it absolutely will not budge above 4000. No blinking MIL or codes generated this time though). So i'm thinking its a speed limiter thing. Will look for another ECU and see it it gives different results.

4Driver4

Why not re-torque the knock sensors? It's never the ECU. Waste of time.

Harddrive2000

Alright, will give it a go.

Harddrive2000

Been driving around for a while now, still maxing out at 85mph, no codes, even when i push her. Still i decided to go ahead and look at the knock sensors afteral, she's got 203k miles on her, anything can happen.

So, i remove the intake manifold to get to the knock sensors. Tedious procedure. Hardest part was detaching the two hoses from the throttle body that connect to the coolant pipes, and the hose that connects to the metal pipe that protudes from the back of the manifold.

Now a curious thing happened as i removed the manifold. I noticed that there were two small yellowish cone shaped pieces of plastic that broke off from the engine block. They are about 3/4" long and are threaded into the block along the same line as the bolts for the manifold, one cone on either row of bolts. They have no structural function as far as i can tell, they are much too soft. They both broke off cleanly leavin their threads embedded and flush with the block. I believe they were designed to do so whenever the manifold is first removed. Some sort of removal indicator. Correct me if i'm wrong on this.

Anyways, i re-torqued the knock sensor on the driver side to spec (it didn't seem to need it though IMO). The one on the passenger side however made me remember that the engineers at VW/Audi can be quite sadistic and for the most part are probably *******s. Why they passed the secondary air system pipe right over the passenger side knock sensor and not simply around it (God knows there was enough room for that) is beyond me. To remove the tube would require removing several bolts in different locations, many of which would be quite tasking. I said F***k it, and F***k Audi! The code i got was for sensor 2 (which i assume is the driver side) not Sensor 1.

Now the discovery. The carbon build up in the manifold and the 6 intake chambers on the block was quite thick. All passages were caked with the black stuff. I could could see the valves and man even those suckers were loaded with the stuff, its a wonder they move at all. Looks like a job for SeaFoam. In the mean time i cleaned up the manifold as best i could and reinstalled everything. Will take her out for a spin tommorow and see what happens. I've ordered the SeaFoam. Will take a while for it to get to me seeing as i dont live in the States.

audinutt

If you have a vagcom cable, download lemmiwinks.
http://www.cardiagnostics.be/now/VAS...Lemmiwinks.htm
This works on DBW (drive by wire cars).

I used it to move my speed limiter on my a8 to 188mph.

I would try this and see what happens.

-Richard

Harddrive2000

Thanks Richard, unfortunately my ECU uses the KW 1281 protocol, hence the lemmiwinks program could not access it.

mtroxel

I feel your pain. I had the exact frustration when I did this job two months ago.

Saw those broken on mine too. Dealer didn't have them in stock, and didn't know what they were for. I assume it's a manufacturing thing to line it up easier. I threw them out.

I don't see any codes for the vehicle speed sensor, but at this point it might be interesting to confirm that it's telling the truth. I believe there are separate sensors for the Speedo in the dash (G22) and the Vehicle Speed Sensor (G68). If your VAG-COM is on a laptop, it might we worth driving the car and fooling with the measuring blocks in the ECU to find how fast it thinks you're going.

Harddrive2000

Excellent idea, i'll give it a shot.

MTykhnenko

Check compression, spark plugs, and fuel pressure. Or in fact your cat may have melted from all the misfiring of fuel into the exhaust, and causes too much backpressure.

Ecu COULD be at fault but its impossible for the limit to be reset on its own to 85mph. Most computers do have a fault with powersupply and if data is being flashed in at that moemnt it could corrupt sectors of it, but corrupting both digits for not aparent reason is unlikely. 135mph = D9 85mph = 88










Sorry, missed the fact that there was a second page. Disregard this.

5v/cyl

More I read about this problem the more it sounds like a limiter or some speed related issue and not the engine. If it will pull hard to redline, but falls on its face at 85mph, then that just doesn't make sense. You have 190+ hp on tap and to run 85mph only requires about a quarter of that power. It would be a turd on acceleration if you only had 50 hp available. If it were me I would concentrate on any sensor that was speed related and maybe ECU problem.

Can you VAG-COM it while your accelerating and watch what the sensors are telling the ECU. Actually have a friend drive and you watch from the passenger seat. Thinking speed sensor telling the ECU that you are at 135mph instead of 85mph causing limiter to kick in.