THROTTLE PLATE SEALS?

[RRoller123]

Are there replaceable seals on the Throttle position switch? Or on the other side where the return spring is? As I continue to track down my idle issue, I am looking to remove all possible sources of air leaks. The plate axle seems like it could be one that would be subtle.

[majicwrench]

You don't need new shaft seals. Look elsewhere.

[chrisfiat]

have you actually tested for vacuum leaks or are you guessing

[RRoller123]

Used a plumbers propane torch everywhere, can't find a thing. Not guessing, going through the entire system looking at every possible location of a leak.

[DanD]

Maybe you should carefully pry the top off your AFM and look at the potentiometer strip. Unless your Brake booster diaphragm has a leak, I'm thinking you don't have a leak.

It is worth noting that every FI fiat I have ever driven hunted and burbled a little bit at idle. Not some, but every single one. And if you look at the AFM internals while the car is running, you will see that the natural tendency is for the arm to move around a bit on the resistor, as everything shakes a bit.

Since you have the throttle switch off, that would be the best time to make sure your throttle plate is adjusted correctly. Close off the IDLE adjusting screw, and set the THROTTLE plate to a very low idle. Then set the throttle switch to activate at that setting, and then adjust the idle screw to your preferred idle speed.

Pop, pop pop pop, Pop, pop pop pop, Pop, pop pop pop. Sounds like you have a percolator in your exhaust ? Maybe that's a pretty normal thing. Run a little Techron through your engine before your next oil change. Sometimes that helps.

I'm going to replace my O2 sensor with my next tune up, and check to make sure the exhaust manifold is tight. I too have been through everything you have, and even replaced the AFM with a much younger one. Still burbles like a Fiat.

[RRoller123]

Thanks Dan, that is good stuff and I will try it, but the symptom that I am complaining about is the tendency for the car to drop to ~200 rpms or so when I stop at a light, nearly but not stall, miss and stumble a little, and then slowly climb back up to about 1000 (gauge) where I keep it set, and run pretty well. This all happens over maybe 4-5 seconds, and is consistent.

[chrisfiat]

it takes a LOT of propane to find a small leak, carefully use an aerosol choke /carb cleaner it will pick up smaller leaks faster, and take a very close look at the air tube from the afm to the intake, these can crack on the underside where the gap is hidden. sounds like you are correct on assuming the situation is a lean one, un plug the o2 sensor and check the sensor voltage as well, and report back, should be around .5 volt lower is lean, higher is rich, the range is .1 to.9 volt

[RRoller123]

Yep, already did the O2 sensor last week, it is fine, just as you indicated.

The main air tube is brand new, replaced because of a small crack found at the AAV stem. Made no difference (other than it now looks better )

[KidDingo]

I have experienced the same thing recently. I used some injector cleaner which helped a lot. After checking, replacing, and adjusting everything air-related, it turned out to be fuel-related i.e. carbon build-up and clogged injectors. The problem isn't completely solved, but it's a million times improved. I think a new fuel filter and and a professional cleaning of the injectors will probably finish the job.

[RRoller123]

Unfortunately I did both a new filter and had the injectors serviced by OK, but maybe they clogged again. Worth checking, I have been assuming that they are functioning properly.

[chrisfiat]

back in the old days before good fuel with good detergents, our fi cars used to develop a carbon build up in the back side of the intake valves. This caused all manner of idle issues from poor starting to uneven idle ( carbon absorbed fuel) . We used to clean it of with a walnut shell blaster , like sand blasting but with walnut shells, worked slick too. i have cleaned them off with a pick and small screw driver as well. if you pull the injectors take a look at the valves, if you see any carbon find a way to remove it, soaking with solvent won't do it this stuff is tough

[RRoller123]

Thanks, that is a god thing to check. I thought I would run some Seafoam through the intake and see if it helps.