Mechanical Aux Air Regulator Maintenance

[RedSquare]

I was doing some general tuning on my 68 FI Squareback today, and decided to give the mechanical aux air regulator some attention. Gave it a test to see if it was closing when warm, and it was not closing. ( I removed the air hose from air cleaner, blocked it off to see if idle drops meaningfully - it did.)

So I removed it from the car and verified that it was very much stuck in the open position regardless of temp.

Pulled it apart, cleaned it up and removed the varnish inside so it would rotate again, then partly reassembled it and watched it rotate when I put the bi-metal spring in boiling water. Didn’t seem like it was fully closing, but airflow was noticeably reduced with the spring in boiling water.

So....put it back in the car, warmed the car up and did the test again. This time, pulling the hose and blocking it off caused a very minor drop in idle. But even when fully warm, the hose that feeds that AAR is still pulling some air.

Is this par for the course for these? Do they ever really fully close? Or is my 50 year old spring fatigued and just doesn’t have enough oomph to do the job anymore?

What say you?

[Mike Fisher]

Djet is old/primitive & will never run like the new FI! Mine runs good enough for me, even if it doesn't start instantly/idle perfectly.
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69 FI/AT square Daily Driver
66 sunroof,67,70,71,71,71AT,72,72AT,73 Parts
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'68 Karmann Ghia sold

Society is like stew. If you don't keep it stirred up you end up with a lot of scum on the top! - Russ_Wolfe/Edward Abbey

[Bobnotch]

[RedSquare]

Thanks Bob. All I’ve done to it thus far is clean it with carb cleaner and a scotchbrite pad. Figured I didn’t want to be removing any metal. From the looks of it, the shaft and body are in good shape - no obvious grooves or scoring on either. I’ve adjusted the spring set position to give it a little more oomph, but there isn’t a lot of adjustment there to be had. Might just be that the coil spring has had enough cycles to have fatigued some and not have the sane range of motion that it used to. (Hey...that sounds like me too!)

Think I may pull it again for one more pass with the scotchbrite pad and carb cleaner, then just live with it. It ain’t perfect now, but it’s one heck of a lot better than it was when it was firmly stuck in the wide open position.

[Dfasty]

Tram recommends a cap of atf in it when bringing a car back to life. my car starts a little easier and seem to run a little better the last time I did it.
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70 fastback automatic 06 invader

[RedSquare]

Thanks Dfasty. I’ll give that a try. I did put a little oil on the shaft when I reassembled it, but it couldn’t hurt.

[RedSquare]

For what it’s worth, here are the photos I took when I was disassembling it. Nothing remarkable that I saw. General grunge that I cleaned off entirely before reassembly.

[raygreenwood]

While I agree that D-jet is old....aside from wear that you have to counteract or replace in certain parts....the AAR, TPS, distributor and TB....D-jet can be made to run actually better than it came from the factory.

While factory tune was "consistent".....it was also a little loose. it papered over the lack of precision in some parts, variances in engine build and just avoided the time required to do the really intricate tuning that was actually possible with the systems that used the three adjustment MPS (middle years in type 3, final year in type 4).

The biggest difference between D-jet in type 3 and in type 4....is that the type 4 had a better throttle body. The biggest single problem (aside from people not doing the required adjustment of their MPS on their no longer stock engines)....is the throttle body wear. The center manifold being the tB on a type 3...and it cannot unbolt like a type 4....all of that gap around the throttle plate seriously screws with your fuel mixture.

All of that said....the AAR. Yes...I agree with Tram ATF is by far the best lube.

The problem with both the mechanical and electric AAR...is that with age....the bi-metallic coil gets weak. So you loosen the screw and tweak it so that now it closes all the way like it should....except that now...the overall timing is off as to how long it stays open. No way around it.

No need for reaming or any of that. Just clean it out and remove carbon and corrosion...but you cannot fix the change with time of the bi-metallic strip.

A big deal for some...no big deal for others....depending....on how your baseline fuel mixture is adjusted and how fast it warms up.

Yep...its age....no way around this with either the mechanical one or the electric one.

I am playing with a "choke cable" set up with a nice boot to one of my gutted electric ones. Going to hook it to a factory two step light switch knob on the dash and see how it works. ....just for fun. A "manual" AAR. Ray

[KTPhil]

I agree... make sure it is closed when hot, and deal with a slightly uneven or low idle until it warms up. Your right foot can compensate during the couple of minutes that it takes.

But the way, a working thermostat makes the engine warm up faster, and so the fix may not be the AAR, but the thermostat!

[RedSquare]

Thanks to both raygreenwood and KTPhil for the feedback. I have yet to take it off again and double check my cleaning and adjustment work, but that is easy enough. The car runs well once warm, and I’m a proficient user of the right foot as an idle enhancer when needed. I’ll look to adjust it so that it is as closed as I can get it when warm. Right now, I think it is set up (not on purpose) such that it is fully open cold, and partly/mostly closed when warm. I just need to figure out if the current level of closure can be improved.

Plus, I now need to go look at my throttle body, MPS and thermostat and learn more about those. Don’t know bubkis about any of them. Not because anything is wrong per se, but I just enjoy digging into it and understanding how the car is supposed to function. I suspect none of them will have had any attention in many moons, so there will likely be more to do there.

It does kind of seem like I have a vacuum leak somewhere - nothing obvious.