weird effect of cleaning TBA
 

Hi all ,

maybe someone can shed some light on this. Before cleaning out the TBA on my 88 240 glt it idled nicely around 900rpm.

So this evening I decided ( and weather permitted) to throughly clean out the

(1) lower assembly where the air duct feeds into . My god the amount of carbon residue was hard to believe. It literally had to be cleaned out in chunks.

:angry2:
(2) Then I removed the bellows ( remembering Mike's tip about using tipex to mark the orientation of the bellows ) and it was the same scene on the actual TBA and butterfly. Large large amounts of black deposits.
:angry2:

Anyways a large full can of Carb spray cleaner later and lots of cloths and all is nice and shiny again.
:Dancing_sorry:

I then removed the cold air mechanism from the airbox ( as per Ian's recommendation ) and fired up the car .

Whoosh now idles at 1400rpm. I had to fully screw in the rpm adjuster screw to drop it to 900rpm. I checked the timing and its spot on .

So I'am wondering have I seriously cleaned something too much or dislodged something within the CI Fuel system , as I had to fully screw home the adjuster ?.

the car drives fine when I took it out for a long drive.

any idea's

regards

brendan

Easy to explain that one :-)

As the throttle has gradulay carboned up and the rpm dropped over the years someone has compensated on the adjuster air by-pass screw , this may have happened three or four times since the throttle was last bright and shiny .. now you have restored the air flow through the throttle at idle there is too much with the additional air coming through the adjuster , so you have to turn it down back to where it should be ..

Excuse my question , but is it the same method on my 2.0i ?

different systems similar methods
 

hi capriman,

My system (CI Injection) would differ to your more modern version as yours won't have the bellows to get in the way. The Throttle body in your case will be where the air intake enter the inlet manifold just after the MAF.

The cleaning procedure involves removing the air-duct tubing from the inlet manifold and then placing a towel under the opening , spray the interior liberally with Carb-Cleaner and then wipe away.

I use a small mirror to see how bad the carbonizations has got in the TBA .

In order to clean the butterfly you will need to manually activate the throttle cable and spray and then wipe away the residue.

hope this helps

brendan

Unless you remove the TBA from the car and unbolt the idle bypass circuit you won't have got that bit clean. Screwed fully home does not sound right. Certainly, as has been said, a good clean can mean you need to tighten it up a fair bit but you still need some air going through. I can't remember if there is a set screw for the throttle stop, but if so this could have been set to leave the throttle open slightly instead of just closed by someone trying to compensate for a clogged idle bypass circuit. The hole for the vacuum advance is quite small and will also benefit from having the TBA on the bench to clean it out. It is not hard to remove the TBA and makes working on it much less stressful on the back. While it is out you can clean the flame trap and all the associated plumbing as well.