1.8t Misfiring. PLEASE HELP

[YourPalBigAL]

First post here on this website...

So my 2002 Audi A4 1.8t is misfiring at idle and while driving. I changed all of my plugs and coils and it still is misfiring. I had a problem with a misfire before and just bought a new coil for cylinder 1 and it ran perfect again. Not the case this time. I tried unplugging my MAF and when I did I noticed that one of the little copper pin connectors is missing, maybe that could be the problem? I cut off both my mufflers back a couple weeks ago, could it maybe be my o2 sensor? It was running fine up until about 2 days ago when I pulled out of my driveway in the cold and gave her some, then got to a stoplight 2 miles down the road and came to a complete stop, then when I tried to take off it was sputtering and shuttering and I had almost complete loss of power. If anyone has any idea about what this could be please let me know. Car has 264,000 and not one problem besides this misfire. If anyone can help save me from being railed by the dealer I would be happy as hell. Thanks!

[elewsader]

Check your coil pack, and fuel injector wiring harnesses, pull back the rubber grommet coverings too..

[Militant-Grunt]

264k miles? Ever do a head gasket on the car? Or any cylinder head work at all?

Id start with a compression test.

[EuroxS4]

check faults and report back.when was the last time you changed the spark plugs.

[h82loze]

Since you've already changed spark plugs and coils, something else you can check is your fuel injectors. All you need is a multi-meter. You want to verify the resistance in the fuel injectors. A bad fuel injector will cause misfires.

[YourPalBigAL]

264k miles? Ever do a head gasket on the car? Or any cylinder head work at all?

Id start with a compression test.

I haven't done a head gasket or any other head work, this could definitely be a possibility. Is there any sort of compression test DIY on this website that anybody might know of?

[YourPalBigAL]

Thanks for all the help guys, I'll check the injectors tomorrow and hopefully that is all thats wrong, if I have to I will pull my head off and check my gaskets to make sure everything is in place, I was smelling oil through my heater, but couldn't find the source of any leak. I'll keep this thread updated for anyone else having this same issue

[YourPalBigAL]

check faults and report back.when was the last time you changed the spark plugs.

I got the car with 223k, and haven't changed the plugs since I got it. (I know, bad nono) So who knows when the last time they were changed were. They were all in O.K. shape didn't seem to be in horrible condition but I replaced them with Autolite Double Platinums.

[EuroxS4]

That's your problem right there auto lite plugs are the cheapest plugs you can put in these cars.These cars don't like auto lite plugs not one bit.Do you still have the old plugs?Id swap in some good known plugs before going crazy.

[YourPalBigAL]

Okay so I borrowed a code reader from my friend who is a mechanic and it spit these codes-

P0420- Catalyst System Efficiency Below Threshold Bank 1
P0300- Random/Multiple Misfire Detected
P0302- Cylinder 2 Misfire Detected (This was a cylinder with a new coil)
P0353- Ignition Coil C Primary/Secondary Circuit
P0303- Cylinder 3 Misfire Detected

My mechanic friend said that I need a new o2 sensor and I should be good. Is he right or what does anyone else think?

[old guy]

You mentioned that you replaced cylinder 1 coil pack in the first post. In your post above you mentioned that you replaced the coil pack in cylinder 2. Did you replace all of the coil packs? Cylinder 1? cylinder 2? Both 1 and 2? What about the other coil packs? A constant misfire is indicative of a bad coil pack. It can certainly be other issues such as a bad injector or plug but if changing the plugs didn't correct the problem the problem probably isn't plug related. Focus on the coil packs followed by the injectors.

Nothing you posted indicates a problem associated with a bad O2 sensor.

[Charles.waite]

The P0420 code doesn't mean anything about the O2 sensor. What it means is the Rear O2 sensor is reporting the catalyst isn't functional any more. Are you running a test pipe?

Be more specific on what you've done to what cylinders so we can be of more help.

Get some cheap NGK BKR6E (6962) plugs and install them in every cylinder. Those plugs are standard copper electrode plugs and will only last for 8k miles, but they WILL work perfectly and are more or less OEM plugs. If the car runs better then you can be assured you had bad plugs. If the car runs the same, you're out $8 but can eliminate the spark plugs as the culprits. Next step would be to eliminate the coil packs.

What coil packs did you replace yours with? Were tehy OEM? If not I suggest you toss them and buy all new OEM coil packs. Cheapest place I've found is amazon for TFSI coilpacks (part number 07K-905-715F). You might be able to pick them up from a dealer for under $20 but its hit or miss if the dealer marks their parts up a lot or not.

Now, FYI, those coil packs are for a b7 2.0t. They are, however 100% compatible for the 1.8t, they just stick up an inch higher. You can mitigate this by removing the rubber boot from your stock coils and sliding it onto these TFSI coils.

[YourPalBigAL]

You mentioned that you replaced cylinder 1 coil pack in the first post. In your post above you mentioned that you replaced the coil pack in cylinder 2. Did you replace all of the coil packs? Cylinder 1? cylinder 2? Both 1 and 2? What about the other coil packs? A constant misfire is indicative of a bad coil pack. It can certainly be other issues such as a bad injector or plug but if changing the plugs didn't correct the problem the problem probably isn't plug related. Focus on the coil packs followed by the injectors.

Nothing you posted indicates a problem associated with a bad O2 sensor.

I replaced the coil packs in the first and second cylinder, I guess tomorrow I will go and buy 2 more new coil packs and hopefully that is the problem. I just got my coil packs from Napa, didn't have time to screw around looking for OEM coils.

[YourPalBigAL]

The P0420 code doesn't mean anything about the O2 sensor. What it means is the Rear O2 sensor is reporting the catalyst isn't functional any more. Are you running a test pipe?

Be more specific on what you've done to what cylinders so we can be of more help.

Get some cheap NGK BKR6E (6962) plugs and install them in every cylinder. Those plugs are standard copper electrode plugs and will only last for 8k miles, but they WILL work perfectly and are more or less OEM plugs. If the car runs better then you can be assured you had bad plugs. If the car runs the same, you're out $8 but can eliminate the spark plugs as the culprits. Next step would be to eliminate the coil packs.

What coil packs did you replace yours with? Were tehy OEM? If not I suggest you toss them and buy all new OEM coil packs. Cheapest place I've found is amazon for TFSI coilpacks (part number 07K-905-715F). You might be able to pick them up from a dealer for under $20 but its hit or miss if the dealer marks their parts up a lot or not.

Now, FYI, those coil packs are for a b7 2.0t. They are, however 100% compatible for the 1.8t, they just stick up an inch higher. You can mitigate this by removing the rubber boot from your stock coils and sliding it onto these TFSI coils.

I have replaced the coils in cylinder 1 and cylinder 2, and have replaced the plugs in all 4 cylinders. That is what I have had time to try so far, been busy with work.

[old guy]

I replaced the coil packs in the first and second cylinder, I guess tomorrow I will go and buy 2 more new coil packs and hopefully that is the problem. I just got my coil packs from Napa, didn't have time to screw around looking for OEM coils.

Here's my recommendation. If you haven't already done so you need to clear all of the DTC's. Then you can see which ones come back. Codes will remain until cleared. Some of them can be from months or even years ago.

When you get your 2 new coil packs replace cylinders 1 and 2 with the new ones. That way you can eliminate the possibility of one of those that have been recently replaced as being defective. If nothing changes then put the coil packs that you pulled from cylinders 1 and 2 into cylinders 3 and 4.

Be sure to closely examine the coil pack harnesses. Unfortunately after 10+ years it is not at all uncommon for the harnesses to crack/split/or short out. You may have a short in one of the harnesses. Pay particularly close attention to the cylinder 3 harness. Cylinder 3 is the one causing the P0353. I suspect cylinder 3 is ultimately going to be where your misfire is coming from. either a bad coil pack or a broken wire in the harness.

Good luck!

[Ricey]

When I bought my 2004 A4 1.8T it was badly misfiring, throwing these codes P0171 P0300 P0301 P0302
Changed the coils & sparks but that did not help

An Audi mechanic told me it was most likely the breather valve (035 103 245) , that got rid of the P03XXX codes, you can take it out and check if the valve is still functioning, worth a shot, cost me €12.56 at Audi

[Audi body]

I had horrible miss fires and it turned out to be the suction jet pump.

[caliber]

My wife's B7 1.8T, 06 production, has around 120K KMs on the clock. Bought it new till now.

Last month, it gave her P0304 and engine light on and flashing. Car was shaking, from idle to whatever rpm. Replaced all coils, plugs still the same. Took it to the garage that has been repairing our cars.

Turns out the compression is low on cylinder 4. Now the engine was taken out for complete overhaul, to replace bearings, valves, pistons and rings, seals and gaskets, water pumps, etc.

I went by the garage and they showed me this. There are other valves that are similar. The car has never been overheated, nor delayed in oil service, and my wife drives it slow. Before this, the maintenance included PCV and hoses, coolant/oil heat exchanger, water pump/thermostat. . No more Audi for me.