2001 2.7TTmisfire. Codes attched... help please!

[K9COP]

hey guys, my GF has a 2001 2.7 6speed A6. When under load in a high gear, partial throttle, it hesitates epically! I'm thinking one of the coils is breaking down. You used to be able to 'drive around it' as VCDS only showed misfire on #2, but now shows on #2 and #4. I think the cat codes are a bad O2 sensor connector as they sometimes come on as you go over a bump. Do I just replace the coils? Thank you, K9 Here's the codes: Address 01: Engine Labels: 078-907-551-AZA.lbl Part No: 4B0 907 551 AK Component: 2.7l V6/5VT G 0001 Coding: 06712 Shop #: WSC 02325 VCID: 6DDBF8D7278ADF1 WAULD64B82N015963 AUZ7Z0A1881780 5 Faults Found: 16815 - Warm Up Catalyst; Bank 2 P0431 - 35-00 - Efficiency Below Threshold 16805 - Warm Up Catalyst; Bank 1 P0421 - 35-00 - Efficiency Below Threshold 16684 - Random/Multiple Cylinder Misfire Detected P0300 - 35-00 - 16688 - Cylinder 4 P0304 - 35-00 - Misfire Detected 16686 - Cylinder 2 P0302 - 35-00 - Misfire Detected Readiness: 0000 0000

[RMsALFA]

While it's possibly the coil packs for 2 and 4, those codes are not a "for sure" indication. Swap them to other cylinders and see if the misfire detection follows - that would be sufficient data for me to replace them.

She wouldn't possibly have a aftermarket ECU tune on the car, would she ?

[K9COP]

I'll try that and update. And no, no upgrades yet It's done a squillion miles so I'll just keep it stock for now I think...

K9

Originally Posted by RMsALFA

While it's possibly the coil packs for 2 and 4, those codes are not a "for sure" indication. Swap them to other cylinders and see if the misfire detection follows - that would be sufficient data for me to replace them.

She wouldn't possibly have a aftermarket ECU tune on the car, would she ?

[RMsALFA]

Originally Posted by K9COP

I'll try that and update. And no, no upgrades yet It's done a squillion miles so I'll just keep it stock for now I think...

K9

Reason I ask is that my APR chip has some annoying hesitations at certain engine temps and RPM that one might mistake for misfires.

[jseklund]

I agree- I would swap coil packs, but I would swap one at a time. I've seen one coil pack throw timing off on another cylinder. You may only have to replace one, plus moving two at a time introduces more chance of mis-diagnosis.

Do you have a green-top coolant temp sensor?

Coils will cost $30-40 on your car, as I believe they are the screw-down type, but my mom has the same year/engine and I think I've only ever replaced one coil on her car - much more reliable.

[K9COP]

I'll try the 'one coil swap' and see what VCDS gives me. $30-$40? where from? The only ones I could find on Ebay were $90, and that's USED! Will check coolant temp sensor too, but why the question?

K9

[GTA_Driver]

An interesting fact: coils on my C5 4.2 are cheaper than on my Mazda 3. Both from their respective dealers.

[jseklund]

Wow - looks like these units have gone up in price a little. They are $50 on ECSTuning.com - but they'll take a while to get to you. The dealership should have them around the same price....$40-60 each.

*edit* - I ask on the coolant temperature sensor, just because it is a cause for all sorts of strange ghosts in this car. My first thought is always the coils for the cylinders, but just something about the situation makes me think CTS as a second thought ...not sure why...it's good to have the green sensor either way.

[K9COP]

I'll do the swap first, then check prices and update on here...

K9

Originally Posted by jseklund

Wow - looks like these units have gone up in price a little. They are $50 on ECSTuning.com - but they'll take a while to get to you. The dealership should have them around the same price....$40-60 each.

*edit* - I ask on the coolant temperature sensor, just because it is a cause for all sorts of strange ghosts in this car. My first thought is always the coils for the cylinders, but just something about the situation makes me think CTS as a second thought ...not sure why...it's good to have the green sensor either way.

[A6force]

Originally Posted by RMsALFA

Reason I ask is that my APR chip has some annoying hesitations at certain engine temps and RPM that one might mistake for misfires.

i have a 01 2.7t that i just put the apr tune on and now it hesitates and sputters under full throttle and then the check engine code will come on for random misfire and for cylinder 3 misfire. tried new plugs and it was find for a day then back to the same problem. any ideas?