hllnwlz

I changed the spark plugs on my wife's A4 over the weekend trying to eliminate variables when diagnosing an intermittent hesitation that was occurring during acceleration. After changing the plugs I took the car for a short drive to make sure everything was ok and the car drove just fine. On Monday morning the car wouldn't start again for my wife.

I tried putting the old spark plugs back in and changing the coil packs (which I knew was likely the culprit of the hesitation anyway) with no success. I have checked all the fuses and I know some level of current is making it to the end of the spark plug wires although I don't know how to use my voltmeter well enough to use it for diagnosis other than there is current reaching the coil packs when the car is turned over. I tried grounding a spark plug in the coil on the valve cover and turning the engine over and there is no spark.

Anybody have any ideas as to what could be going on?

Thanks in advance,
Kyle

One

So power is getting to the coil packs but no spark when cranking?

jseklund

CTS is my first guess.

lyleswk

CTS? Coolant Temp Sensor?

jseklund

Yes - but just a guess. You should pull the spark plug and the coil and then ground the electrode to the cover while it is in the coil. Be careful not to zap yourself- it will hurt. Have someone crank the engine and look for sparks.

jseklund

Sorry - just saw that is what you tried and got no spark.

Is this happening for all 6 spark plugs?

I'm not sure - but the things I would look for if you're not getting any spark and you have new packs and plugs are the power output stage, the wiring to the packs.

I did a quick search and it looks like the "hall sender" may also cause a no spark issue.

lyleswk

Failed CTS will not prohibit the car from starting, just will not allow the ECU to control the thermostat for optimum engine temp / performance.

Hall effect sensor is know as an ESS (engine speed sensor) on our cars and yes, it will inhibit the car from starting.

ECS Tuning-Audi

Do you have access to vag com?

If you do I would scan the car for codes. This will give you a good starting point.

Jason

Trase103

this ESS is only on the B6? do B8s have them too?

lyleswk

Should post this on the B8 area, but given that crank position is one of the key signals to the ECU, I would assume the 2.0 has one, but don't have any direct knowledge. Did you post over there?

Also, do you have a code reader?