Help - 2.0 will not idle - (with story)

[bkreigsr]

I replaced my air filter element yesterday in conjunction with an oil / filter change.
I put it back together and now it will not idle. - I mean drops to below 1,000 then just disappears.
I'm going to retrace my steps today but I thought I'd bounce this off the brain trust.

Is there a hidden hose behind the air filter assembly that is commonly missed?
I looked for loose hoses flopping around but came up negative.

FWIW, the 2.0 is in my 912E. And, it ran/idled fine before I started to mess with it.

Thanks in advance, Bill K

[jess p]

There is an O-ring in the oil filler cap. That cap needs to be tight, it’s a large source of vacuum leak.
Then there are the fittings to the air intake and the electrical plugs to the air box and the throttle position switch, they could have loose.

[bkreigsr]

Thanks Jess.
I did flip the oil filler cap gasket, just to get a new sealing surface - I've got to see it it's still in there and making contact. Moral - if it ain't broke, don't fix it.
All electric connectors i checked seemed to be in tack and connected, doesn't mean I saw them all.
...will report back.

Bill K

[Dave at Pelican Parts]

The 912E ran L-jet fuel injection. L-jet hates vacuum leaks. Look for any where you might have dislodged a vacuum hose or otherwise introduced an air leak.

Also look for any wires you may have disconnected accidentally. I once spent a day chasing a no-start because I had bumped the CHT sensor connector on my car.

--DD

[bkreigsr]

Thanks Dave. I've done all that. The CHT 'looks' like it's still in tact.
Car is being trucked to the shop. I give up.

I tried to drive it there, but could not get out of my neighborhood. Ended up down the street and killed the battery cranking. Walked home, replaced battery with a fresh one, and pulled back into the safety of my driveway.

I've got a feeling I'm in line for a new AFM. I took the connector off while I had the snorkel out and there was one black spike in the row. Also, looks like the PO had some work done on the unit.

This is turning into on expensive oil change.

Bill K

[jess p]

That engine in your 912 was the same engine in my 75 914. Maybe Dave can chime in on this but with the ignition switch turned to the on position, you can depress the little door in the AFM and that will initiate the fuel pump which you can hear. I don’t know if that in and of itself clears any fault with the AFM. I hope it is not your AFM, they are pricey. There is an NOS one on Craigslist Phoenix. It was always a superior pain to run down problems with that L-Jet system. I still have some good working fuel injection components you are welcome to have if you need them.

66 912
65 912
66 912 with 914 2.0L
70 914
71 914
76 911S
82 911SC

[bkreigsr]

...., and we're back....
Our cable has been out since the hurricane rolled through here on Tuesday. (Still no power)

I narrowed the problem down to the Mass Air Meter. I removed it on Monday to record whatever part number id's I could find. I did find the Bosch number, but not a Porsche number (- should be a 923 xxx number). I put everything back together except the flex air duct that traverses under the MAFM and the vacuum hose from the Aux Air Regulator. Took it for a brief road test - and it worked fine - all fixed - end of problems. ...NOT !

I reinstalled the hoses and it was the same as the no idle situation before.
Conclusion - the harness that plugs into the MAFM is messed up, or, more likely the connector itself is messed up. (You can't reinstall the passenger side hose without jostling the harness)

I could not order on on Pelican or EBS, I see their point, as they don't accept returns on elec parts anyhow. So rather than pay dealer prices, my tuner can get it cheaper, then mark it up, and the onus is on him to get it running correctly.

Hopefully, he will do a continuity test on the 7-pin harness before he orders a new unit. That part of the diagnostic equation is beyond my pay grade.

Either way, at 125,000 miles, and three prior owners, of this euro delivered car, I'm probably due for a replacement air flow sensor.

For those keeping track on their score cards;
the Porsche PN is 923 606 111 00 (I think)
the Bosch PN is 0 280 201 006

Appreciate any comments or suggestions.
Bill K

[jess p]

If you remove the 7 pin connector from the AFM the connector will be numbered 27-36-6-8-8-7-39. Now as you remove the 7 pin connector those numbers will be a mirror image on the AFM. To verify the AFM is a good unit with an OHM meter check resistance between
Pin 6 and 9. 200-400 ohms
Pin 7 and 8 120-200 ohms
Pin 6 and 27 2000 ohm
Pin 36 and 39 infinity with door closed and 0 ohm with door open
Note that you should have 12v coming from the dual relay from 88z and 88a

If you are concerned about the 7 pin connector then trace those 7 pins back to the hookup on the electronic control harness module. Visually inspect that the 7 pin connector to see if the pins are not bent or broken. Do not dismiss the AFM unless you have done the above checks. Ive seen used junk ones for $600. I’m not certain that 028 200 006 AFM will work on your car. Stay with 028 201 006.

In the process of changing your filter element you must have disrupted a connector. Go through the process again before throwing new parts at it. Are the connectors snug at the dual relay?

[jess p]

Correction........To my above post I misprinted... 7 pin 27-36-6-9-8-7-39

[bkreigsr]

Thanks Jess. As mentioned, all elec tasting is above my pay grade, but I'll give it a shot before I send it out to these folks:
Air Flow Meter Service - Bavarian Restoration

Also, thanks for the update.

Bill K

[Dave at Pelican Parts]

I believe that the 912E air flow meter is at least calibrated slightly differently from the 1.8's. Witness its 923 part number, for 912E only. If you swap in another meter, you may find the mixture is not quite correct under some circumstances. You can verify that with a wide-band O2 meter if you want to be sure.

Your comment about the air duct under the AFM worries me. If there are holes in any of the stuff that is "downstream" of the air flow meter, that will let un-metered air into the system. Which will result in a lean mixture and idle and driveability problems.

--DD

[bkreigsr]

Dave thanks for the reply.
The referenced flex air duct is similar to a 911 set-up. Two hoses (one-each heat exchanger) go from the fan around the engine bay firewall and end up in their sockets in the engine tins (bumper end of the motor).
So, no air is tapped or introduced into the vacuum system. The flex hoses only push hot air up to the cabin. (theoretically)

...and yes, you are correct about the 923 part number. A number of components have been tweaked by the factory to accommodate the larger valves and bigger cam.

Bill K

[Dave at Pelican Parts]

Ah, got it. The heater ducts, as you say, don't introduce any "false air". I was worried you meant something else, like the big rubber duct from the AFM to the throttle body. If that breaks, it's a Very Bad Thing.

--DD