On a very cold day, after being parked outside at work, my 1998.5 a4 2.8 started misfiring (shaking at certain rpms) and a flashing CEL came on. I limped it over to a friends house and left if in garage for now.

Couple questions if you don't mind:

- is driving it in this condition a few miles (if I baby it) a big concern?

- would I be able to get (meaningful) code info from a n 'oreilly obi scan' or would i have to vag it to get problem isolated?

- without a crystal ball, is this likely to be a coil pack/ plug wires or?

- could a bad coolant temp sensor cause these issues?

- any other suggestions?

thanks.

 

Flashing CEL means you have a serious misfire, and are likely to be causeing damage to the cat, by running rich exhaust gas into it. Keep the driving down to a minimum unless you want to buy new cats.

Sounds like a bad plug, or one of your coil packs is toast. I'm assuming the 98 2.8's have the same coil pack configuration as a 96 where you have to replace all three coils at once.

If you have an induction type strobe light, put it on each spark plug wire until you find the wire/cylinder that causes it not to flash, that would be the dead one.

 

Hi - thanks for replying.

no, believe mine has the central ignition coil, like this:

 

- could a bad coolant temp sensor cause these issues?

 

That coil is similar (but not the same) as my sons 96 2.8L coil. Looks like yours has the ICM built into it, my sons doesn't have that finned box. Much easier and cheaper, to replace a 1.8L coil on plug than these type.

Don't think a bad temp sensor will cause it, but its possible I guess. A bad one will make the car almost impossible to start when cold, acts like a flooded carburated vehicle and is very hard to start, if you can get it started it misfires until it warms up.

 

on my 98 A4 i had the same symptoms. after running the codes it was a number 2 misfire. I pushed down on the spark plug wire and it was as simple as a loose connection and no problems ever since. Lets hope its that simple for you as well. Good luck.

 

Yes, that would be awesome if that end up being the case.

I ordered a basic vag reader: (Car Code Reader Scanner VW/AUDI SCAN TOOL MAXSCAN VAG405 VAG 405 OBD II OBD 2 EOBD2). That I'm hoping will at least get me the basic diagnostic info I need. I'm not nuts about driving it in present condition - so hoping this will work.

What I'm not sure about is if scan shows xx cylinder is misfiring (and assuming t isn't simply a bad connection), how I go about isolating if it is: plug, plug wire, coil, or something else?

I'm not opposed to replacing coil pack ($180), wires ($100) and plugs (cheap), but don't want to do all that and then find out it is something else.

Any tips / suggestions ?

 

VAG COM will tell you which cylinder is misfiring, as far as figuring out if its wire, plug or coil, just replace the bad cylinders plug, they are only 3 or 4 bucks, and then recheck. If the misfire hasn't moved, swap two wires that are about the same length. If it moves then its the wire, if not its the coil, or ICM, assuming you don't find any other codes like a bad cam position sensor, or crank position sensor.

 

UPDATE:

ordered a vag scanner and got these 4 engine codes:

16684-35
16686-35
16684-163
16686-163

(all of them had kwp1281 listed too)

The scanner didn't have definitions of these codes, but think that at least one or more relate to 'misfiring'

ALSO DONE:

I popped off the vanity covers and pulled up each of the six plug wires. Left/Passenger side seemed fine/dry/normal.

3 plugs on right/drivers side (which I think are cyls 4-6) came out soaking wet in oil.

LOOKING FOR SUGGESTIONS:

Not sure where I go from here. In other words, Assume right bank has issues, but not sure I've narrowed much down yet in terms of the true source of issue yet. I'm kind of guessing/assuming I have valve cover gasket issue on right side.

I'd be fine with the bearing the cost of valve cover gasket and/or plugs/wires and even coil pack. BUT don't want to do that unless I've ruled out bigger more costly problems??

 

16684 is random multiple misfire, and 16686 is cylinder 2. So the cylinder 2 misfire pokes a hole in your oil on the driver's side bank theory.


Two thoughts on the driver's side oil/plugs issue:


1. I've spilled oil when I fill it, and had the spilled oil end up in the plugs on that side.
2. Could just be a bad valve cover gasket on that side too.


Either way, I think the oil on the plugs is making a mess, but not any misfire.


KWP 1281 is just the communications protocol, not a code. Completely normal.


Go to RossTech to look up those codes, and they suggest where to go with them.


Category:Fault Codes - Ross-Tech Wiki


I'd look at all the things they suggest for those codes.


I don't think it's a bad coolant temp sensor. That gives a different symptom....more like a hesitation in some situations. I think you've got some full misfires going on.