C4SnNJ

Have a recurring P0302 misfire. Originally was a P0302 and P0300 random. Cleared it and it came back after a few days. Usually happened the second drive of the day(4-5 hrs after drive in to work). Did a search and many recommended plugs and coils. Car has 57k so I figured plugs and coils couldn't hurt. Replaced them, cleared the codes and drove home. No ck engine on way home. Started this morning, no MIL on way to work. Went out for lunch and, bam, light came back on. Checked code and now it is only the P0302. Car runs fine, no bucking, shaking, no flashing light, it maybe runs a little rough at idle when the light comes on but this could be my paranoia.
What is generally the next thing that one should check? 1)Swap injectors between #1 and #2. 2) Run some sort of injector cleaner through the gas. 3) Run a smoke test to check for vacuum leaks(would a vac. leak be so specific for just one cylinder?). 4) buck up and take it in to the dealer.

Thanks for any help in advance.
Pat

Tippy

Swapping injectors will be one of the hardest things you will do on the car. Those rails are on there!

Who replaced the coils?

C4SnNJ

The injectors did look kinda time consuming. I run a service dept., albeit a Kia dealership, but the tech used to work at our VW store and has replaced 1,000s of those on the 1.8t motors.

Macster

Tippy asked the right question: Who did the spark plugs/coils? I'd double-check that spark plugs are properly torqued -- loosen then retorque.

(Another question would be what did the old plugs look like?)

However, odds are long that 1) you got a bad plug; or 2) you got a bad coil; and 3) you (or whomever did the work) installed the plug wrong; or 4) installed the coil wrong; and 5) in the same cylinder as before.

Long odds.

But... last thing touched is first thing suspect: There is the question -- which possibly only you can answer -- is are the plugs the right ones (each and every one -- do not rely upon box markings but check every plug's marking) and were the plugs checked for any signs of cracks or damaged electrodes? Even a new plug can be bad. Ditto a new coil.

Be sure every spark plug's coil pack connector securely connected. Remove each one and listen/feel for a positive release. The connect and feel/listen for a positive connect.

Misfire is likely not an intake system leak.

If you find spark plugs and coil packs ok, then I think a bottle or two of Techron mixed according to instructions -- or just dump a 20 gallon bottle into tank and fill up gas tank with fresh premium gas then repeat for another tank. I like to change oil/filter after using Techron.

See if this helps. Misfire could be from intake valve deposit build up, fuel injector build up, etc.

If at any time engine starts to exhibit any other symptoms with the check engine light on, or off, best to shut the engine off and have an expert look at engine preferrably with as little engine running as possible. None is ideal.

That the misfire remains with the same cylinder suggests something specific to that cylinder at root cause.

Misfire could be precursor to bad VarioCam actuator or even a burned valve to name just a few possibilities.

But see if revisiting the spark plugs, coil packs turns up anything and give the Techron a chance to work for you.

Or try the Techron first if you are sure the plugs/coils ok.

Sincerely,

Macster.

C4SnNJ

Thanks Tippy and Macster. I'll have him recheck the torque. I looked at the coils and could see no evidence of cracking and the plugs looked ok. They weren't dark or white. I have some Techron on the way. I'll try that and see how it goes. So you are saying 2 tank treatments cycles? Would a bad variocam actuator be that specific for just one cylinder? It's just strange that it never happens, knocking on wood, on the intial run of the day.

Macster

Hard to say regarding a bad VarioCam actuator that it would manifest as a misfire at only one cylinder. However, when the CEL comes on you may change your driving style which delays anyhow any other cylinder misfire error codes being logged. Thus the #3 cylinder looks like it stands alone when if given more driving time the other cylinders on that bank may also have a misfire error code logged for them as well.

Also, not all cylinders are created equal. #3 may be more sensitive to any variations than the others on that side of the engine.

However, it does suggest the cause of the problem is confined to that one cylinder.

That you never see the error on the initial run of the day suggests to me that a fuel injector gets weak (or misbehaves) after some running time.

Do not know how hard it is to do, but swapping #3 injector with another cylinder's injector (or just replacing #3 injector -- though I hate to just replace parts with no more reason than one hopes doing so will "fix" the symptom) might be worth considering.

But see what Techron does for the engine first.

Sincerely,

Macster.

function12

Could be a stuck lifter.

C4SnNJ

Well, it's back. I put in the Techron on 10/02 and there have not been any misfire faults since. I drove in this morning w/o a hiccup. Then when going out for lunch, after running the car for about a minute the MIL came back on. There are more codes this time. P300, P301, P302 and P303 misfires. From what I understand these are all isolated to the one side of the engine(is it drivers or passenger?). Macster mentioned something about a possibly bad Variocam actuator. Is this a terribly hard job to do? Anyone know the approx. $$$ amount for this repair? I don't mind experimenting as long as I am not getting over my head. Is the cam actuator the same for both heads? Can they be swapped? Or should I just suck it up and go to a specialist?

Macster

What do long term fuel trims look like for both the "bad" bank (#1) and the good bank (#2)?

Also, does it appear the exhaust system is not blocked on that side of the engine? Does the exhaust system look ok, no signs of any cracks or other damage?

I helped -- via posts -- somone on another board through a VarioCam actuator job on a Boxster. How much I contributed to the successful outcome I don't know and what's worse I do not remember much of the details. There were a lot of back and forths and issues with verifying the camchain timing was correct. IIRC the person was able to get in there and do both sides with engine in the car.

Vaguely recall a buyers guide article on 996s that did state actuator failure a possibility and replacing them of course the solution and here's where it gets vague, that this can be done with the engine in the car.

However, I would not advise you to tackle this job on my terrible memory until you have a much better feel for what the job will take and of course whether the job needs doing in the first place.

It is rare, but not unknown for an intake manifold to leak so I'd be darn sure I eliminated that possibility.

And another possible cause is fuel supply to the problem injector fuel rail on that bank is being interfered with. Not sure how, but my point is that all other possible causes need to be eliminated as best as one can.

Even after you've eliminated (as best you can) other potential causes of the misfire how to verify outside of removing hardware and getting to the actuators the actuators (or the rails, chains, etc.) are the problem I can't tell you.

I suspect a shop with the proper Porsche diagnostics computer could do this, but I make no promises.

Sincerely,

Macster.

Paul Conquest

Since the problem improved (became less frequent) with a fuel change, I would look closer at the injectors. Maybe have the injectors cleaned ... there are treatments that can be done in car.

Sticking lifter is possible. Could be some galling in a lifter bore causing the lifter to bind. If this is the case, I would expect it to happen at higher RPM.

Is the Variocam working? You should notice a change in engine tone under load at 4000 RPM (Variocam changes intake cam timing increasing intake:exhaust valve overlap) and again on the 3.6 at 5200 RPM (Variocam2 sends additional oil into the lifters to increase valve lift).

What oil are you using? And is it getting colder where you live? Porsche specifies synthetic 0w/40, 5w/40 and 5w/50, however since early Jan/2001 the factory fill has been 0W40. My hypothesis is that the change to lighter oil is due to the 3.6 engine needing a thinner, easier-flowing oil to pump up the lifters at higher RPMs. I drive my C4S all winter ... but with thinner oil than summer.

Macster

The most likely reason for Porsche going to to 0w-40 is to improve its CAFE numbers. Other car makers have been lowering the viscosity ratings going from say 10w-30 or 5w-30 to 5w-20 or even 0w-30.

My 02 Boxster ran just fine for nearly 80K miles on mostly 15w-50 in the dead of mid-Missouri winter cold to the high 90s of the summer. Course it has run fine on approx. 80K miles of driving with 0w-40 and nearly that many miles again on 10w-40 "high mileage" oil. Oh, car with orignal engine has 226K miles on it.

Having a sticking lifter is rare. About the only thing I can think of is the oil hole from the oil galley to the lifter bore is blocked, but the zero lash adjuster would click like crazy I would think.

A good injector cleaner is Techron. One or possibly two treatments -- as per directions -- should suffice. I know some shops will pull the injectors out and treat them to a special cleaning but I wonder if the cost of this approaches the cost of just replacing them all with new ones.

Sincerely,

Macster.