914-912E smog stuff discarded

[Dearindeed]

I removed smog pump tubing from my heads and promptly lost one of the fittings when obtaining a like-threaded plug. Now on startup it roars up to 4K rpm and likely dies regardless of idle-valve opening. Since I don't know if reverting to the tubing, (which would only cushion exhaust pressure since it was blocked from the smog-pump input afaik,) would resume normal running, has anybody a clue about this? If you can even figure out what this says, do anybody know where info exists for motorists who have removed some or all of their smog-control equipment? Thank yeu

[raygreenwood]

[Dearindeed]

Thanks a lot for replying; My motor is from a 912E and has no tubes in the valve covers. The fittings I removed are the California pump inlets that add Oxygen to the exhaust for combustion in the can added to the manifolds before the heat exchanger. I found a couple plugs from a spare head and a bicycle axle with the matching threads cut in half. I suspected the throttle valve switch which wasn't on my bus, (by which I'm supposed to be familiar with this engine, or not,) but guess I'll measure things with what tools I have. It seems there is no vacuum leaks if it's giving itself so much gas with no pedal input; disconnecting the cold-start wire didn't change things. It's as if the spring which closes the flap in the airflow meter broke, but I don't know where the air is coming from if the throttle is closed; the only route between the exhaust and intake valve is through the cylinder.

[raygreenwood]

[Dearindeed]

OK I found the 4th smog pump fitting in the mobile tool bag, saving $75. Removed all the plugs without dropping too many parts in the tin. I was expecting to be driving around, but refitting the smog equipment changed nothing in the faulty operation.

PLUGGING UP SMOG PUMP FITTING HOLES DOESN'T BREAK FI MOTOR

So if this topic has any value it may persuade people who've moved out of CA that setting aside their smog pump equipment has no adverse effect, in agreement with the most recent reply to my request for help in figuring out why on starting up the air/fuel system acts like the pedal is floored and dies, even, from one or two tries, when I open the throttle pedal halfway during the similarly rapid decline in RPMs.

I'm having trouble accepting the good advice of making sure the S-tube coming from the flap is cracked, has holes. That helps explain where all the air is coming from, with a closed throttle, but it means the cold start valve dumped way more gas than before. It makes me think I didn't rightly hook up the fuel pressure regulator, which I'm used to having its input line holding it to the front tin. Or maybe I broke the flap spring dicking with the CO adjustment.

At any rate, I know this has to be something I caused by trying to fix what turned out to be a loose plug, which was in a head I thought I wrecked when a plug without a barely visible helicoil wouldn't thread in. So I must have broken something when tightening a plug would have fixed everything, or mucked things up removing the tin to get at the plug hole. It was a lot easier to fix this motor when it needed to be fixed more often, but I guess I will very carefully check the rubber stuff since listening might help me fix it.

[raygreenwood]

Bear in mind......with fuel injection you are allowed "0" vacuum leaks.....period.

If anything....any hose or boot...allows air into the center plenum or intakes....downstream of the throttle plate .....it is air.....that has bypassed the metering unit....therefore the metering unit adds no fuel for that air dosage.....so you run lean.

Likewise......a crack or hole in the boot between metering flap and throtgle plate....lets the throttle plate draw in air....that has not moved the flap......to allow fuel allotment for that air.....so you run lean.

Also.....any vacuum leaks in the center manifold....affects the vacuum signature to the fuel pressure regulator.....generally cauing you to run ric at the wrong time.

Yes.....plugging the exhaust gas pjmp inlets has no performance .....other than it will require usually a slight tweak to the CO mixture and idle....due to the valve overlap buult into the camshaft. Ray

[Alan Brase]

Not sure about the 1976 912E heads but what works quite well on 73-74 bus heads with smog tubes removed is late valve adjuster screws. the big ones. I just used old worn ones and locktited them in.
I had a 912e once and I think the smog tubes are similar.
Al
_________________
Al Brase
Projects: 67 sunroof bug, 67 Porsche 912 Targa, 70 Westy
Dec 1955 Single Cab pickup WANT 15" BUS RIMS dated 8/55, thru 12/55
To New owners: 1969 doublecab, 1971 Dormobile
Vanagons:
80 P27 Westy JUL 1979, 3rd oldest known US
83 1.6TD Vanagon, 87 Wolfie Westy daily driver, swap meet home

[Porsche Driver]

Vacuum, vacuum, vacuum

Ray was right, check the rubber boot to AFM. Considering the 912e will not run well with vacuum leaks, I became a fan of self vulcanizing silicone tape! This stuff is not sticky and will self cure itself to form a tight seal. I used it to fix the rubberboot flexible part and it worked great.

Another frequent leak ares is the 90 degree angle rubber boot at oil filler. Remove and inspect as often they are cracked below outside visable area. I replace these things with silicone 90 degree part (original but the original rubber NLA).

Also check all connecting pipes/hoses to this rubber boot.

Check all hoses, once more... and replace them as you will not spot tiny holes. It's not costing a lot to do but will help you in finding the issue and get a reliable nice running engine.

Ensure that you blocked off correctly as it sounds like a major leak to me

Another item to check is the rubber on the idle adjustment screw, very easy to replace, but can be area of minor leaks as well on this engine.

There are a few more options, but if engine ran fine before them unlikely these will be the cause out of a sudden.

Good luck with finding the issue, very rewarding once found and hear a nice spinning engine but be patient.

[[email protected]]

coming into this late, if you have a high idle on a afc injected 912e, either the throttle is open, or the intake air is bypassing the throttle sucking the air flow meter door open. Not a common scenario as in d jet cars. USUALLY, the throttle body boot splits, air comes in from the atmosphere, and the air flow meter door therefore does not react and the car will not idle. (same thing when the oil cap seals are bad) Disconnecting the emission tubing at the heads would not cause this, but there they connect to intake system could