Lifter noise on a Boxster?

[Ronzi]

So, I climb in the Box last evening and crank it up. It runs like crap (missing, stumbling) for a few seconds, accompanied by a sharp metallic tapping sound. I shut it off and start it again. Same thing, but not so much missing. Again. Same thing. The fourth time the tapping is less. I decide to let it run. After about 15 seconds the tapping slowly subsides and the engine smooths out and runs normally. After 80 miles of driving, it is still running normally.
If it was a small block Chevy I would say it had a stuck or collapsed hydraulic valve lifter. Am I hearing the same thing from the buckets on the ends of the valve stems? I undrstand these are oil-fed to eliminate valve adjustment.
Has anyone else experienced this?

[Subanez]

I have issues with my Mass Air Flow sensor, and after about 5-10 seconds, the engine smooths out. Its also accompanied by the tapping, or clicking, that sounds exactly like the lifters, as you said.

I brought it into the shop about 2 weeks ago, and they said the sound isn't bad, but once I replace the MAF and reset the ECU, I'll know if anything else is going on there.

So any chance your MAF is going? I could be way off, not claiming to be an expert here or anything.

[mrmickeymouse]

What was your temp [ambient], also what type of oil and weight were you using.

Miles on motor?

The noise is normal to some extent [as you know.] The stumbling is weird though, it almost sounds like a mis-fire condition.

Maybe a MAF problem which fixed itself, have you had any prior problems.

[Ronzi]

Much obliged for the quick responses.
The car is a '99 with about 29k miles. I bought it in April when it had about 26.4k. No service records with the car, other than one oil change receipt from a Porsche dealer dated April of '03, noting the use of Mobil1, weight not specified.
I have had no problems with the car whatsoever since purchase. No error codes have been spit out, either.
Ambient last evening was about 71F. I noticed because it was exactly the same as the cabin temp I had set.
The day before (Wed.) I had gone into the engine compartment and sucked the dust off the engine with a shop vac (no leaks anywhere), and pulled out the air filter element and sucked the little rocks and whatnot off the foam thingy. Did I get the element in backwards maybe and that is somehow screwing up the MAF?

[Ronzi]

The filter element issue appears not to be the problem. I looked at it again, and it only goes in one way, with the foam side of the element to the air intake, and the pleated paper side to the engine.
One thing I did not mention is that last night when the problem appeared, the exhaust smelled really weird, and strong, when I started it up. Not the rotten-eggs smell of a loaded cat, but just really weird.

[Ronzi]

Googling on "Porsche hydraulic tappet" yields a bunch of info related to the ticking or tapping noise in Porsche and other engines caused by the hydraulic tappets. Apparently this is not an unknown problem, although high mileage would appear to be a factor. I wouldn't think 30k would qualify.
My 30k major service is coming up shortly, so maybe some fresh oil and filters will clear it up.
I started it up again a little while ago and got 3 or 4 soft ticks, then all was quiet.
Still doesn't explain the poor running or the stinky exhaust last night.

[mrmickeymouse]

I think you answered your own question, when you vacumed out the air filter area you probably got something into the air way. The bad side is that the something may of been eaten by an intake valve, albeit the valve noise.

Here is the bad part: hopefully it was soft and eaten by the car, I have a 135,000 miles and I have the oil refill noise upon every long time sitting.

I have had that noise with every motor with mileage e.g. Toyota, VW, etc...


If it continues, running bad again, you may of damaged the MAF. Hopefully not a valve.

[Ronzi]

Shaking some gunk into the intake, thus fouling the MAF (temporarily, I hope), does make sense with the poor running, and perhaps consequently the strange exhaust smell.
The tapping may have been a coincidence, because the car had been idle for over a week when it happened.
Thanks again for the help.

[Brad Roberts]

When it was running bad... what kind of RPM where you seeing ?

Just curious, *maybe* the "lifters" didnt get a chance to pump up because of the low idle conditions that normally exist with a MAF issue.

Something no one asked: How long had the car sat prior to you firing it up and hearing the noise ? Lifters bleed down. This is VERY common issue with the 944's (and they run a very similar lifter to the 986)


B

[Ronzi]

The car hadn't been run for maybe 10 days or so.
On initial startup the rpm was pretty low, nowhere near the proper idle speed. Probably less than 500rpm. I shut it off almost immediately, maybe 5 secs.
The next couple of startups were better, i.e., not so much missing, but I didn't really look at the tach. My impression is that the rpm was closer to normal.
Now that you mention it, that 10 days is probably one of the longest intervals without running since I bought the car. That said, however, when I started it again the next day, I got a few ticks before they went away, and prior to this problem the engine had been totally quiet on startup.
Much obliged for your interest.

[Brad Roberts]

You had a combo of things happening. The low idle could have been caused by the lifters losing their oil which in turn wasnt opening the valves far enough. This would have caused the injection to freak out. It didnt see the vacuum signal it was supposed to see.


B