Ninespub

Last weekend, after just removing the broken-hose in-tank pump (replaced with a filter) main pump, filter and having the MAF rebuilt by Kevin at Injection Labs, today, I'm finally back on the road. HOWEVER, when I am at idle, and especialiy if I'm in park, I'm hearing from inside the car (even with a an x-pipe burbling) a clicking sound like something is flying around in the intake. It's intermittent and sometimes its REALLY loud. '91 $4-automatic w/145K miles BTW.

A full intake refresh was done a couple of years (and only a 1000 miles) ago by a very experienced local 928 enthusiast so I'm confident about that work. The car was experiencing a lot of the expected flooding, chugging, backfiring and missing while trying to figure out the recent core issues as noted above; and I'll presume that that was a good reason why I smoked the electronics in the MAF as well as the wire.

WTF could be flying around? Could the backfires have blown something off or broken anything in the intake? It almost sounds like a very small pebble or screw etc., but the intake hasn't been touched. So nothing could have gotten in there unless .................something could (possibly?) have entered the intake through the MAF opening?

Experienced 928 gurus: Sorry for the long post but I'm trying to give as much info as I can so you can help me....hopefully.

BTW, Should I park this car (again) till its figured out?

SteveG

If there is something rattling around inside, you do not want it getting to an intake valve or worse in the chamber. And how did it get in there? Is the air filter seated properly? The screens on the MAF? The MAF boots? A stethescope might help. If it was mine, I think I wouldn't even start it til I removed the intake and checked this out.

Mrmerlin

I would remove the MAF and inspect the throttle housing also consider removing both of the side plate covers check the flappy with a mytivac to see if its opening also inspect the flappy throttle plate

Alan

I too vote for peeking past the throttle plate & then if needed taking the intake side plates off to see whats up - this could be a disaster - I wouldn't run it like this...

Alan

Maleficio

Does it respond to RPM changes? Or is it constant? Any chance it could be in your HVAC plumbing, but sound like it's coming from under the hood?

Ed Scherer

And are you sure noise isn't coming from lower down, like... loose flex plate bolt?

Also, in addition to using a stethoscope to try to localize the noise, you might also be able to snake an inspection camera in and visually check things out.

Ninespub

To all the reponders: thanks for the current imput.

Malefico: Its inttermitent, but yes, there seems to be some sensitivity to rpms. My AC does not work so HVAC fan speed would not seem to be a factor; although it was quite loud in the cabin the last time it happened, and the sound did seem close to the dash. Interesting thought though. I heard it outside when the hood was up and it truly sounded like the intake area. The fellow who put the fuel pump on and checked the MAF brought it to my attention and I didn't hear it prior to the current work being done. Again, could something have fallen in when the MAF was removed and be laying in there getting pounded by the intake turbulence?

Ed: Its not from below, but I'll try to see if I can localize it better Friday or Saturday.

Ed Scherer

Just in case...

Are you familiar with the "tapping from the center vent" problem? I'm not sure if you'd hear it from the engine bay as much as inside the car, but just one more thing to consider.

See "Weird sound from dash, HVAC?" (there are also many other threads on the subject that a search would probably turn up).


I'm not dismissing the likelihood that the problem really is in the intake area; I just want to make sure the other "well-known frequent problem" possibilities are quickly eliminated.

Ninespub

Ed: I read the thread you brought up and it is something I'll look at, but what I have seems more like something that is a flying-around-sorta-noise. I mean that it does not sound like its from a specific area but more like each "hit" is from a different spot within that area......if that explains it at all more better.

Jim M.

Could it be a valve lifter? Does it go away after it's running for awhile or when it's warmed up? Best idea is to pin point the location of the noise. Either use a mechanics stethescope or a long screwdriver with the handle on your ear. Move them around to different points on the engine (cam covers, water pump, intake manifold etc.).

Ninespub

BTW gang, my automobile mechanical abilities are somewhat limited to light wrenching like small switches, window motors, seat removals and fuse/relay swaps due to time and certain limited physical restraints. However, I can mix a helluva drink, pour a great beer or fine wine and deliver a juicy char-grilled steak in my restaurant. Just sayin.....so I basicly have to translate what I see/hear/know info to you and then copy/relay the responses to someone else.

SeanR

Just to cover all bases.

Did you check the PSI level in the right rear tire?

:P

Ninespub

Sean, that photo is a couple years old now, but I'll check tomorrow to see if its the same as it was then. Smartass (meaning that in only the kindest way)!

Maleficio

It would be cool if you could hold the car upside down and shake it til the thing falls out.

Ed Scherer

So, Paul, did you ever figure this one out?