Oh yeah i love seafoam and i highly recommend it to other members. 2.8L's do get a lot of carbon build up on the intake valves but it usually causes a no start concern when i come accross them. Another old school trick similar to seafoam would be to spray carb cleaner directly down the intake with the engine running and have a buddy rev the motor. That also works pretty well.

 

There I was thinking my troubles were long gone, but in fact they are still alive and well. After the car had cooled the misfire returned, same P0305 code, etc. It does idle much better when warm but cold idle is terrible still.

Here's what I have done since: Removed the intake manifold and literally flossed the valve stems using yarn and Deep Creep (Seafoam in a can). The valves didn't look bad at all since I have Seafoamed 3 times now!! The stems weren't bad either but now are beautiful as far as I could reach.

Since the valves will close immediately when I remove the camshaft, I suspect the lifters are stuck in the extended position and for some reason will not bleed down. I have lifters on the way so I will change at the weekend.

I've been Googling and reading like mad and I think it is entirely feasible that I have failed lifters.

Fingers crossed!

 

Good luck with that man! Here I am bothering you with my troubles and not realizing that you got your own crap to deal with!

 

New lifters and still not right!!!!

The really annoying part here is that I drove the car after putting in the lifters and it was really smooth at idle, no shuddering at low RPMs, basically felt like it should. The next time I drove it the MIL came on, P0305 again but it still felt pretty good. Then later I started it up and it ran like a bag of s**t.

My problem is obviously intermittent, which seems very weird for a valve problem. I am going to go and do a leak down test next to confirm that the misfire is compression related still. Assuming it is, I am struggling to come up with a theory on what might be wrong. I didn't touch these valves and they are not bent because they seal when they want to! The best theory I've got is weak valve springs, but why??? And why two adjacent valves? (One of the three behaves normally).

 

OK, leak down test completed - all very normal on no.5. So now what????

I repeated the leak down 4 times - turned engine by hand between tests. Ever heard of a leak down that gave a false positive result? I'm new to leak down testing so I have nothing to base the results on other than my Harbor Freight gauge thinks no.5 is as good as no.4 and 6.

The plug in no.5 had plenty of wear, although it only has a couple of hundred miles on it. I cleaned and re-gapped it. It is a Denso Iridium which is supposed to have a very long life! I put it back in no.6 to see if I could make the misfire move and subsequently got a P0305 and P0306. I reset them because I couldn't remember if the P0305 was from the old plug or not, then I got a P0300. If I remove the injector connector from no.5 the engine doesn't get any worse, so no.5 is still bad in some way.

The injector is clicking nicely....

I checked the coilpack on no.5 and it gives a nice strong spark so I left it there.

I wish I had a VAG-COM! Maybe this week.......

I really don't want to pull the head if I don't have to, and right now I can't see a good reason for a valve issue to be at the root of all this.

 

Try swapping the coil pack to another cylinder and see if the mis-fire follows it. Most problems of this nature are electrical!

Bob

 

I agree - it has electrical written all over it, but I have switched no.4 and no.5 coil packs with no change in running or codes. The one currently on no.5 has gives a nice strong spark using a spare plug - wish I had tried the actual plug from no.5.

I read elsewhere that a guy with same symptoms eventually replaced the ECM. I hope that isn't my issue!

 

I'm worried that I might be speaking too soon here, but I think I got it again!

I switched the primary stage amp modules, got P0305. I switched coilpacks between 5 and 6, P0305. I switched coilpacks between 4 and 5, P0305.

Then, I cleaned the contacts on the coil connector and got a smoother running engine. So, there was more where that came from - I pulled back the boot on the connector and found oil on the wires, so I cleaned them up with contact cleaner. Same for the injector plug - some oil under the boot there too.

I drove the car twice and got no codes!! Not even pending codes, which has never happened before. We'll see in the morning, might even take it to work!

 

Such a wierd problem, cleaning the electrical connectors made it better huh? That would be a first.

 

Yeah, maybe would have been a first if it had worked! I drove to work in it this morning and everything seemed to be fine, but when I checked I had P0305 again! I definitely fixed something because the idle is smooth and there is no shudder at low RPM's. VAG-COM shipped yesterday so hopefully I will be able to get some quick insight into what influences the misfire by looking at the misfire counts.

I think the cause of the excessive oil behind the connectors (all over the wires under the boots) was a shaky hand filling up with oil - it would dump all over no.5. Not my shaky hand!!