MosTT

A week after changing plugs my 01 TTQC developed misfire and very poor running suddenly while running aroung 65. I rechecked plugs, wires etc and problem remained. I have several broken connectors because of heat but the plug in portion was good. I took it to a local Independent Mercedes shop no VW or Audi dealer in my location. I do essentially all my own repairs but did not have a code reader. The local person ran codes and decided to order and replace coil pack without telling me what the codes were, said the new iridium plugs were fouled and replaced them. The harness wires show breaks too and I plan to replace wiring harness. Anyway, now it will not start. He says no power to the new coil packs. He says he did a repair of wiring harness, coils and ecu on a vw that had a similar problem. After viewing many posts on this and other forums, I suspect the coil connectors were connected wrong and caused another problem with the ecu or something else. He had taken loose all the vaccum tubings and removed and tossed the heat shield from the wiring and had it hanging over the engine. There were many breaks in the wiring covers. The part that looks like a resistor he says is the radio spark static supressor has the wire broken from it. It had been attached like a ground to the motor. He says it is not important. I refused to let him do anymore work and had my TT towed home. I have taped wires and disconnected battery to reset ecu. No luck no start. Any pointers will be helpful. Any one have a link or picture of proper orientation of plug in connector to coil. There are numnbers 1,2,3,4 on connector at wire connections do they face up or down toward engine when connectecd to coil. How can I test ecu on vehicle, Is there a fuse for the ecu. I dont want to tow vehicle 130 miles to Audi Dealer.

AudiMick

The resistor thing is indeed a spark suppressor for the radio.

You need access to a Bentley and a VAG.com.

There are probably codes stored and disconnecting the battery is usually pointless on OBDII equipped cars.

The wiring manual for the TT is about 80 pages long. 11 diagrams for the motronic alone for the 2000/ 2001.

To start the car you need.

Air, fuel, spark.

MAF ,IAT, CTS, Camshaft position sensor, crankshaft position sensor, ECU, fuel pump, coils.

I believe black/ violet is power to the coils.

MosTT

I checked the old coils and they have numbers for the wiring. I see the connectors were flipped and plugged in wrong. Yeah, I know Japanese makes would not allow this to happen. In this case the connector clips had broken off all so there was only the numbers for orientation (or the dismantler paying better attention to the wires). The #1 pin on the coil and wire connector is on the passenger side and # 4 on the drivers side. Any thoughts, what may have been damaged by the reverse wiring. Basically the hot wire was connected to ground and vice versa. I really hope there is a fuse somewhere that protects the ECU. I corrected the wiring and tried to start again with no better results. Possibly both the new coils and ecu are damaged. I need enlightenment.

MosTT

Problem solved. After re-orienting the connectors with the blue and red wire to #1 (towards passengers side), I decided to go back to the basics. If something electrical does not work look for a fuse or breaker. I found fuse #10 blown. The owners manual lists one of those half sized 10 amp fuses. The "mercedes person" had aparently placed a 15A fuse that was blown. After changing the plug Varoooom, back to the races! Lesson, the coil connector can be pluged in wrong if the other attachment pieces are broken. Even though the passanger side of the coil is square the insides are rounded the same on both sides. The 2001 TTQC manual lists fuses 10,29,34 & 43 as Engine Timing Fuses #29 is 15A and the others are 10A. I returned the Auto lite iridium plugs and the sales person said they should have been gaped. They were set at .040. Maybe they were the problem from the beginning. Oh well, now I have new coils and NGK iridium plugs. Will do onlay VW 1.8T coil wire harness soon.