Bill,
The next time you have that injector in hand , there is a quick & dirty test that works on Toyotas and other lesser cars - but may not be sophisticated enough for Porsches .
Hook a short length of tubing between the injector and your air line: With a good shot of WD-40 in the tube and ~25 psi air, intermittently touch 12v to the contacts.
Hopefully, there will be no premature .. ah .. 'dribble' - and then a perfect climactic cone pattern on contact.

Sounds strange, but has worked for me ... Oh, and kill the cigar first ..

 

I am still fighting this idle surge. Youhave my moral support bill, and I wish I could help. FWIW i extended all my wires, and did not move the ground. But am going back in to solder them rather than press on connectors.

Re: the vacuum line below the bypass valve: nothing done to it yet. Will have it extended by my welder to get a good purchase.

The shark also ate a power steering belt yesterday, so I know the feeling.

 

I think you guys should measure CO at idle. This is because the O2 loop and the ISV system will fight each other for control is for some reason the idle fuelling isn't near enough to get into loop range for each of the two loops.

A simple measure of O2 sensor volts would be a good start, but even better would be a CO probe before the cats.

Bill, maybe you should look for any stored O2 loop fault codes with your "Spanner". You can also use it in "Actuator test" mode to check the drive circuits to the ISV system are working OK.

Best regards

 

John:

No 02 codes. My surging is gone for now.

Hey, John - when I select "clear stored codes" from the LH diagnostic, the unit just sits there "working" forever. On both cars that I tried it. Disconnecting the battery should clear the codes, right? The Spanner doesn't seems to be able to.

The dead hole is still there and did not move, so I ruled out the injector itself, but not much else yet. The blower bypass that dumps near the affected hole was carefully sealed to the manifold. It may have an internal leak, for all I know. Hard to evaluate that. Besides the dead hole, the idle is quite good now.

 

Adam:

The belts needs careful alignment and must be VERY tight. I had problems with walking PS belt. After getting the alignment right and setting it tight, it stayed in place during the race and thereafter. The air pump pulley on my car has an off-center wobble that casues the belt to walk no matter what you do. The center of the pulley is slightly larger than the shaft. Mine needs a thin bushing or spacer. I had to run the race w/o that belt.

 

Hi Bill,
I can't explain the non clearong fault codes, haven't come acroos that before. You can delete the codes with a battery disconnect, but you will loose the adapatation parameters as well.

Glad to hear the idle is smooooth...

Can you check the cam timing on the #7 side through the vent holes in the cam covers ? The car I know of that missed at idle, but ran smooth at higher level was out on cam timing on that bank.

Regards

Regards

 

KISS I'm tellin' you, it sure sounds like a vacuum leak, either the intake manifold passage at #7 is not sealed properly, or possibly a PCV hose is loose or leaking causing the miss at idle after warm-up. I've seen this before on other cars. I'd carefully shoot some carb cleaner around the intake port & vacuum hoses.

 

Bill:

Yes, the fact that this appears only after warm-up speaks to a poor seal that is expanding. I'll try the carb cleaner squirt.

 

Sounds like you may have two problems and they are not blood relatives. Surge may be a vac leak or electrical problem. Have you considered a smoke test of your intake. I saw this done on a 911SC and it (pardon the pun) smoked out no less than four leaks. As far as the rough idle, and I am going to show my ignorance here since I am very new to 928s, could you have a mal functioning lifter on cly 7. Hydraulic lifters are very reliable and have few problems but I have seen them act up. You might have a little "tick, tick" at idle, very hard for someone over 40 to hear. Just a thought!

 

You started with: "The first person who provides a suggestion that leads directly to the discovery of the cause of the problem or who successfully guesses the cause receives a very nice set of Porsche crest aluminum valve stem caps in thanks for their contribution to my sanity."

So who won the valve stem caps?

 

*bump*

I know it wasn't the injector, but Bill did you ever solve the problem?

 

Since I haven't posted any suggestions I'm staking claim to the "Do nothing and hope it fixes itself" fix. So if it has fixed itself I'll be happy to take the valve stem caps, thank you.

 

The surging was probably the ground for the idle stabilizer/MAF/throttle positisn switch. It acted up briefly again a few weeks ago but cleared up in a day. Weird. Some kind of intermitent break. The behavior of the last episode was odd....

Restart car after running great for weeks and driving it for a bit one morning and I get thick black smoke and rough idle. Undo the battery ground and reattach and that goes away. Start to get wildly oscillating idle, even dies at times. By the next morning that is gone. Fine ever since.

The dead hole at idle only is still there, but it is still a very minor issue. When I install the intercooler I ordered I will very carefully re-seal things.

 

This was my take on it.
The location of the bypass valve may have some influence on the #7 or #8 fuel delivery. At idle/off boost the bypass is open allowing air to in essence bypass the supercharger, not allowing it to compress air. The bypass basically links the exit of the SC to the inlet...sucking air from the exit of the SC and delivering it to the intake.
In doing so i think the airflow and/or fuel delivery is being effected slightly by this. Perhaps enough to induce a miss or a bit of a rocking idle, which tends to be more apparantwhen the engine is warm i have found.

Hopefulley the pics below show whati mean.

 

Tony so your thinking a lean condition misfire caused by unequal air distribution that would be consistent with it being worse when warm since a cold engine gets a rich mixture during warm up.