CIS Thottle Shaft Seals

Cipotifoso · 07-07-2007, 03:45 PM

In my search for possible sources of air leaks on my CIS system, I have to wonder about the throttle body shaft seals. An exhaustive search on this forum revealed nothing. Yet, a test on mine (crude - blowing on the passenger shaft seal area with the unit out of the car) reveals that it is not air tight. This should have an effect on the metered air, but nowhere that I can find has anyone replaced these seals.

Naturally, I'm assuming that there are seals on the throttle shaft. It could be an O-ring sealing the shaft or perhaps only the bushing/bearing and no seal???

Assuming there are seals used, a general web search revealed a web site called DSM (1990-1999 Eagle Talon, Plymouth Laser, Mitsubishi Eclipse, Galant VR-4, and any Evolution!) cars in Canada (http://ca.dsm.org/). They tackled this problem using seals sourced from Kaman Industries (http://www.kamandirect.com/). Another source they used was from a company called Chicago Rawhide. I imagine that if the dimensions are known, the seals could be sourced there.

Has anyone ever attempted to replace these seals? Is the leakage at the throttle shaft insignificant enough not to worry?

1982911SCTarga · 07-07-2007, 04:44 PM

This is a good thread in that you've raised an interesting question. I've seen any number of used CIS throttle bodies on the swap scene, which leads me to suspect that a fair share of them possibly were replaced with new in chasing mysterious CIS air leaks.

If a worn/leaking throttle body can be be repaired and brought back to snuff, that would be great. Hopefully, some resident CIS experts here will contribute to this thread.

Brian

Cipotifoso · 07-08-2007, 08:11 PM

I know that there are a lot of people here who know a lot about CIS. Hasn't anyone ever gave this potential leakage source any thought?

Cipotifoso · 07-09-2007, 05:46 PM

bump

ianc · 07-09-2007, 10:11 PM

Surprised no one has chimed in on this one, so I'll give it another bump. Way back when I worked as a VW mech, throttle bushings on carbs regularly caused smog problems on older engines, so I've kinda wondered about this myself.

Be interested to hear some more knowledgeable opinions,

ianc

1982911SCTarga · 07-10-2007, 05:40 AM

I'm puzzled why this topic isn't getting interest. To add to what Ian points out, air leakage in the throttle body shafts of MFI systems is a well-known issue, too.

On this question:

Quote:

Is the leakage at the throttle shaft insignificant enough not to worry?

I would think that any air entering the system through alternative (or unintended) means would be undercutting optimal CIS performance. I'm viewing this in terms of stacking error tolerances, such as multiple air leak sources in a well-used and high-mileage CIS-equipped car.

Brian

Paulporsche · 07-10-2007, 06:16 AM

I think you have the interest, as evidenced by the number of hits. I'm not sure there is too much knowledge available on this.

Cipotifoso · 07-11-2007, 06:45 AM

I would guess that the consensus is to set the CIS a bit richer to compensate for the leakage from the thottle shaft area???

I did an initial measurement on the shaft/bore and came up with 7mm / 18mm. After some searching on the internet, I found a place with 7 x 18 x 4.5 nitrate seals. If they are available in small quantities and after rechecking my measurements, I may try to fit them to the thottle body. I know that there is enough room on the side facing the fuel distibutor. I'll have to remove the thottle lever on the driver's side to verify if there is enough room there also.

If anyone has tried this or thinks that I'm barking up the wrong tree, please let me know!