MFI throttle body butterflys are loose/rattling, how to fix?

BottleNose · 05-21-2006, 11:41 AM

Was driving my 1973 911E and I heard a mechanical "chink chink chink" sound coming from the engine compartment at idle. When I looked I saw that the shafts inside the MFI throttle bodies (which move the butterfly valves) were wiggling in place and making the noise. With the engine off I could wiggle them myself and there is quite a bit of play. I could do this is only on the pax side throttle body, and the car runs perfect.

Looked in 101 projects and it says that when this happens its because the butterfly bearings are worn out and it's time to have the throttle bodies rebuilt. Who does this, how much will it cost, and is there any way to do this oneself? My MFI pump was DOA when I bought the car, and thanks to the MFI gurus here I revived it myself.

Thanks for any advice.

jluetjen · jluetjen's Garage

You don't say where you are located. Matt at Eurometrix does a really nice job rebuilding MFI throttle bodies. I'd give him a call.

- John

bavaria911 · bavaria911's Garage

Email Robert in Germany who sells the rebuild kits (bushings) for the throttle bodies.
Just tell him Scott mentioned it to you (the US Army guy in Germany). Robert is very knowledge on MFI throttle bodies and has written a few articles in German and English on the subject.

robert.wartanian@web.de

Do it and save yourself $800.00

vr,
Bavaria911

lateapex911 · 05-21-2006, 01:05 PM

bavaria, do you have any idea of the cost? i'm thinking of using some MFI throttle bodies for a project, and if I could use old S versions it would be a lot less than just rebuilt S versions! (And finding GOOD S versions seems tough)

BottleNose · 05-21-2006, 02:48 PM

Eurometrics wants $1000+ for one side...yowza! Thanks for telling me about Robert. Has anyone here actually performed this rebuild? How difficult was it and were any special tools needed?

David E. Clark · 05-21-2006, 03:35 PM

Quote:

Originally posted by bavaria911
... Robert is very knowledge on MFI throttle bodies and has written a few articles in German and English on the subject ...

Any chance you can post the article(s) here or email me a copy? Thanks.

Jandrews · 05-21-2006, 03:48 PM

I'm interested to see where this thread goes as well. I think the price on these throttle body rebuilds are a tad outrageous, and it would be great if there was some kind of alternative.

JA

Scott Clarke · Scott Clarke's Garage

Are you sure that was for one side? I had both of mine done by Matt for less than that three or four years ago. Unfortunately, it is not just a matter of replacing the bushings. The wear you feel in the bushings means that the throttle plates move back and forth, creating wear in the throttle bodies. Matt provides new throttle plates a millimeter larger than original, and bores the upper part of the throttle body to match. As a bonus, it is very inexpensive to have the throttle bodies enlarged to S spec at the same time.

Matt's work is first rate. The throttle bodies come back with freshly plated and/or new hardware. They are flow tested, so you don't even need to adjust them. They look brand new.
-Scott

304065 · 05-21-2006, 05:00 PM

The E cam is not what I would consider a mild cam like an SC cam, it has a decent amount of lift so there will always be reversion throughout the rev range, you can just hear it better at idle. Also you might be hearing the high-frequency squeal of the injectors firing.

Just that clattering in the absence of some OTHER check-measure-adjust related problem does not justify rebuilding the TBs. If you can't get it to idle at all, that would. Likewise, when you remove the throttle body and hold it to a light, and there's enough of a gap that you could throw a small rodent through it, it's time for a rebuild.

Scott Clarke · Scott Clarke's Garage

As long as the idle isn't high, you likely don't need to worry about it. My car wouldn't idle at anything less than 1200 RPM.
-Scott

Jandrews · 05-21-2006, 06:14 PM

That's where I'm at, Scott. My car wants to idle at around 1,200 rpms, unless I tighten the air adjustment screws just about down tight. But then, when you do that, you get uneven enough airflow that the transition from idle to part-throttle is not terribly smooth. Leaky throttle shafts, basically give you 12 (instead of 6) sources of air into your combustion chamber at idle!! Unlike the air adjustment screws, these "leaks" are not adjustable...LOL. I think a rebuild would do me good, but at 7,300 rpms, I think the last thing my motor is thinking about is a little air coming in through the throttle shafts! Hard to justify this kind of expense when the car runs great at wide-open throttle. However, if there were some inexpensive alternative, that would be appealing. But, based on what a true rebuild involves, I guess a cheap alternative is probably pretty impractical.

JA

304065 · 05-21-2006, 06:24 PM

John, don't give up and have them rebuilt until you have taken them completely off the engine, soaked them in B-12 for a couple days and reinstalled them and completely run through check measure adjust. If you can get a set of the protractors that will help with the transition also because you will have the angles correct.

You could see good daylight through my starboard stack and I was able to get perfect correlation within the range of the adjustment screw with a 900 RPM idle. The key is the throttle stops, air correction jets and the rods must absolutely be adjusted right, then setting the pump is easy.

The MFI Diaries: Correlation at LAST!

john walker's workshop · 05-21-2006, 06:32 PM

sometimes just a little spring tension on each set of linkages will keep the clatter down and the idle too. make a couple of 2" tabs that attach to the rearmost throttle body stud and connect a return spring between the tab and the rearmost linkage ball.

Jandrews · 05-21-2006, 07:39 PM

Ahh...now we'ren getting creative! John_C, thanks for that encouragement. I am hoping Zeke gets those protractors done and I can pick up a set from him. I know you have been to the wall with this, and I appreciate your guidance here.

JWW, as usual, comes in with a good idea. I think I will try both of these steps to see if I can clear things up a little on the low end transition.

JA

bavaria911 · bavaria911's Garage

Gents,

I received the article from Robert. It is in German and English.
I can't post it here because it is an Adobe file. I will email it to Dave Clark to post with all the other MFI data.

Question: There is a "Company" that rebuilds throttle bodies (it is mentioned on this board at times), please look at the picture...doesn't the brass disc with the .6 stamped on it... face down towards the head intake? In the picture I believe they are installed upside down. I have seen four sets of factory MFI throttle bodies and all of them have the .6 stamp facing down because it is due to the angle cut on the edge. Chime in if I'm wrong.

Vr,
Bavaria911

bavaria911 · bavaria911's Garage

Here is the picture on their website:

Halm · 05-25-2006, 06:13 AM

Quote:

Originally posted by BottleNose
Eurometrics wants $1000+ for one side...yowza! Thanks for telling me about Robert. Has anyone here actually performed this rebuild? How difficult was it and were any special tools needed?

Just checked Matt's website. It is $1,080 for a SET, not per side. As others have described, there is more to this than just replacing the bushings.

bavaria911 · bavaria911's Garage

Anyone know the answer to my above question to the t-bodies brass disc??

Bavaria

jluetjen · jluetjen's Garage

Matt has some special tooling that he uses to refurbish the butterflies (the brass disk you were referring to). Since he's starting out with essentially a new edge, he then cuts it as appropriate to fit the throttle body. To make a long story short, he may machine it so that it fits best "upside down" to it's original configuration. Kind of like flipping a syncro in the transmission.