mirousse

Intake manifold and valve covers are removed for powder coating.

While I have access to the the throttle body assembly, should I give a special care to the idle speed adjuster / throttle valve switch / MAF? The car has no issue. I normally replace hard to access parts but changing those is expensive and probably an overkill.

Your thoughts?

Michel
89 S4 ROW

davek9

Hello, year and car model please?

mirousse

Sorry..89 S4 ROW

FredR

The idle valve adjuster thingy has a tendency to accumulate a disty residue in my experience- good if you can clean it out to stop the shuttle from sticking. whether you can or should use a carb cleaner in there debatable. I used patience and a clean white cloth until I could see little further pick up. worked fine after that [was sticking previously].

The throttle switch contacts tell the brains whether the car is in tickover mode or yahoo mode. Generally the tickover switch contacts operate flawlessly but the full throttle contact has a tendency to fail at the soldered connection inside the switch. there is a comprehensive thread on this. It is possible to cut open the switch body and solder it up but whether it is a suitable candidate for a pre-emptive strike while you are at it not so sure on that one. for sure you should test that the switch contact are operating but you cna do that without having to remove the thing.

Regards

Fred

davek9

Yep first clean and inspect the parts, test the WOT switch w/ multi-meter (two settings, Idle and WOT) making sure repeated attempts work. Clean out the MAF, consider sending it out for a refirb. Also I would replace both Knock sensors in the "V".
Just consider the Time & Pain (a maybe the cost of a tow) to remove the Intake once again verses the cost of the parts that you do not change.

Dave

mickster

Replace the Throttle Valve Switch (Aka TPS). Many threads on those who learned the hard way...ISV-can be cleaned but...while you are in there...

mirousse

Does the TPS require an adjustment for positioning? Are the screw holes larger for a rotating adjustment?

davek9

Yes they are slotted and you rotate the switch, should see yellow paint on the factory position setting. You should not need to remove this switch to do any testing unless you are replacing it.

auzivision

TPS should be adjusted to to 'click' when the throttle is released to idle although it will run (or I should say idle) just fine if it's out of adjustment.

IIRC the tps has three designations (idle, cruise, WOT) which relate to three different fuel maps. So if clicks going into and comeing off idle as well as somewhere around 75% throttle.

The throttle bearings/seals are another cheap WYAIT maintenance item.

mirousse

This question may not make sense but...when the car's idling, is the throttle flap completly closed or slightly open? If closed, where does the air comes from?