OK I searched the threads and none of them match my issue exactly... Hope y'all can help since I only have a week before I head to Afghanistan and I'd like to fix the car in time to get a few more runs in at the Nordschleife before leaving for the year...

A couple months ago while driving to the 'Ring I got a bad misfire (cyl #2--I keep a Peake Research diagnostic tool/OBD-II reader in the car). I limped the car home and pulled the plug...it was completely fried (actually welded one of the 4 "tips" to the electrode). I picked up a new set of JCW plugs from the local dealership (80 Euro! ) and was on my way...car ran great.

Then a couple weeks ago the car starts to run like crap again and I swapped the wires and plugs again (new wires and iridium plugs this time). Car ran ok for a day then ate the #1 spark plug. Completely dropped the ceramic insulator down around the electrode/tip.

Getting worried now... I swapped in a JCW plug for that one and the car ran "ok" but didn't seem as strong as before. Soon after that I got the DSC light and SES lights along w/the P0304 code--misfire on cyl #4. I've been getting this code almost continuously since then. I can clear the code but it comes back after a short drive.

Sometimes I get just the DSC light, sometimes DSC light plus the SES light... Sometimes no lights at all but the car runs rough--eventually one or both come on though.

I swapped the cam angle sensor today and the car still runs rough.

Beginning to think serious problems like a head gasket but I'm not burning oil or losing water...and there's no oil in the water nor is there any water/coolant in my oil. I've checked continuously for a week now...

The plugs seem fine...nice light gray/light brown residue on the plugs indicating a good burn.

I do get a lot (~1/2 cup every week or so) of fluid in my oil catch can... It looks exactly like oil/water mixed (frothy milk-chocolate color) but it's not--there may be some oil from the crankcase vapors in it but it smells like rancid gas or maybe old nasty antifreeze (don't know of any other way to describe it).

I don't seem to be burning more fuel than normal but I suppose I'm getting some blow by w/all the misfires, etc.

Coil pack possibly? I tried swapping plugs and wires w/known good ones (between cyliders on my car and from another set) and still get the P0304 code.

Help! I'm stumped short of pulling the head to check the valves and valve guides but don't want to go there unless I have to.

 

Meant to list the engine mods: R53 w/Alta intake, +17% supercharger pulley and 2% underdrive crank pulley. Cat back exhaust.

Not getting ANY other codes besides the P0304 (not P0340 btw).

 

91 my friend @ his shop. His car. Same thing. We tried to swap the engine control modules,plugs wires ,coil packs. no change misfire cyl#4. Erase comes right back.

1. do a compression check cyl#1-4 compare
each cyl should have somewhere from 135-150 psi.

2. Do a compression leak down test.
I bet you have a burnt exhaust valve or maybe a head gasket issue.
hard to say.

3. I will keep you informed. But pls do those checks first.


Guido mini Tech out!

 

great idea... I thought of that late last night too. I have a compression tester and will check as soon as I get back from Hockenheim this afternoon.

I'll post the results but I'm starting to think valve guides or seats (hope its not the valves or piston rings).

 

OK, did the compression test and I think we've found the answer... Compression on cylinders 1-3 is right at 142-143 PSI. Nice consistent readings after multiple tests.

Cylinder 4 is reading just under 100 PSI. After checking that cylinder before and after the other three, I poured a cap full of motor oil into cylinder #4 (~ 1/4 ounce) and ran the test again to rule out rings... The pressure got up to 105-110 PSI but nowhere near normal or near the other three cylinders.

Guess it's time to pull the head.

I just went over 30K miles today and that coupled w/the mods likley = no warranty work though I'm pretty sure I'll find excess carbon buildup in the head. I was also getting this issue intermittently before any mods and my car has always had a very pronounced "burble" from the unburnt fuel but again no way to prove that so I'll likely pay for the repairs out of my own pocket.

Looks like it's time for an upgrade! I'll run it as-is for the week and then drop it off t have teh head pulled. If the head is still good as a core I'll likely go w/a Thumper or some other performance head.

A local tuner has a nice one that he sells but it's pretty spendy w/the $-to-Euro conversion right now. He actually just sold the local BMW/Mini dealership to concentrate on his race team(s) so maybe if he pulls the head for me and it's clearly an issue w/the OEM valve seats or whatever he can sweet talk them into a warranty repair/replacement.

We'll see...