Yup, I replaced the CHT with a brand new one from Porsche. Heading out on vacation tomorrow or so with the family. I've parked the car for now. It runs very good at speed, but not so good at idle when warm (sometimes). I have a new throttle screw, perhaps I will install that before I leave tomorrow.

It surely feels like an idle vacuum leak, but I haven't found squat!

-Wayne

Thanks for the thought - I tested all the fuel pressures, and I've now replaced 100% of the fuel lines - same issue exists...

-Wayne

So, it has been a few weeks; has there been any new tests or progress?

Last I heard it was stolen, again, and Wayne had to file an insurance claim.



Just Joking!!!

Been on vacation in Montana and Idaho, so no progress until I return!

thx,

Wayne

Okay, so I got back on Friday. Installed the new seat belts (what a pain - they didn't fit properly and required seven modifications per side to get in there), and took it for a drive. It didn't magically fix itself by sitting (that rarely works indeed). I also replaced the idle screw (cleaned it out and replaced it with a new one with a new o-ring). That also didn't make a difference.

The car runs very good when driving, but idling, it's still flubbing and missing and all that. Warming up, again, it seems to run fine. When slightly warm (one min), the idle drops and it starts to flub at idle. I just ordered new injectors that are AC DELCO alternatives - Sal gave his somewhat blessing in this thread here: http://forums.pelicanparts.com/porsche-911-technical-forum/327832-alternative-fuel-injectors-17.html They are OEM cross-references to the -364 injectors, so they *should* work okay.

Remember, when I plugged in Steve W.'s borrowed injectors, it ran much different / better, until after a short while, it started running crappy again. Indeed, I thought that this was due to crap in the fuel system (which would have then clogged up Steve's injectors. So, I had mine cleaned again (one came back dead), and then reinstalled them again. Same problem.

So, twice I sent my injectors out, and twice they came back as indicating they had problems, and twice the cleaning did not fix the problem. Steve W. and I think Sal too have both mentioned that sometimes injectors just go bad and no amount of cleaning will help. Not sure, but it's worth another try. Again, I swapped around injectors previously, with no discernible difference.

If the new injectors still do not fix the problem, then I think the only thing left to try is to change the chain tensioners. If one of them is lagging at low rpm, then that could explain the left/right imbalance in the mixtures. Unfortunately, with these very early, primitive engine management systems, there's no way to measure bank-to-bank cam timing and any differences. On the Boxster, you can do this test, and it's quite useful for determining problems with the chain, the tensioners, or even the IMS bearing (sometimes). But alas, there's nothing on the 3.2 motor that will assist you with this. As some of you may recall, I did check the cam timing and it came back within spec (as best I could check it on a 914-6 with the engine still in the car!). I may or may not be able to replace the tensioners with the engine still in the car - the motor mount is welded to the front bulkhead, and may not allow enough clearance for that. It's important to note that I do not hear any major rattling or any other chain tensioner noise, except for what sounds like a "slap" when the car misses.

Anyways, that's the update! Thanks,

Wayne

O2 unplugged permanently? They run better that way. The flubbing after one minute could be the O2 kicking in.

Yes, still unplugged...

-Wayne

Does this motor have a non-stock cam? If so what cam is in it? These motors can tend to idle a bit erratic with non-stock cams, and they need to be in the 13.8 to 14.2 AFR at idle to idle decent, they do not like to idle leaner than 14.4 when warm. Also note that an injector with a spray pattern issue will act up more at idle at very low pulse widths (very short on time). Hopefully those aftermarket injectors you ordered help?

I'm fairly sure it's a stock cam, but I haven't owned the motor since new, so I suppose anything could be. The injectors I ordered are the AC DELCO ones I displayed here:

http://forums.pelicanparts.com/uploa...1589796255.JPG

-Wayne

With more time behind me than ahead I don't screw around with anything that's not cooperating.

Since the car is a GT look it's a natural for a pair of 46mm PMO's. I'm reasonably sure Richard would look out for you.

The best part is the 46's are easy to tune. Fuel and fire and off you go. No electronic EFI BS.

So far, 24 pages of nothing but a headache.

What is your time worth?;)

So... where is your wideband 02 sensor plumbed in at?

... You know, the tool you need to actually see whats going on...
You'll need one even to get a decent tune on Webers without guesswork, because reading sparkplugs does not really work with modern fuels, except (maybe) race gas.

The better units even have a programmable narrowband output to hookup to older factory FI rigs to make them run at the afr you want them to.
.....................
This could be something as simple as a vacuum leak, or grounding or even fun with 30+ year old factory efi wiring harness. A good start would be finding a local shop that can do a smoke test, although there are other ways to test...

I would normally suggest dropping one of the newer efi systems on it... I have been daily driving Megasquirt "junk" for over a decade now, I and a lot of other folks can create solid tune on a normally aspirated car in half an hour given a few freeway onramps and some light throttle cruising/city traffic. The tuning and log analysis software is excellent.

Also, the ability to datalog everything at up to 400hz makes diagnostics a thing.
(MS3 to a fast internal SD card, good subset, you choose what you want to log))

The reason I wont suggest that is you say the car drives fine, and just stumbles at idle... something that NEVER would happen with Webers, because they contain magic fairy dust...
:rolleyes:

Webers do make for great throttle bodies btw... The music a set of independant runner itbs or webers make is almost worth it, and with a good programmable EMS they can be almost as drivable as the EFI setup you have.

One last thought... There are folks that make super quality replacement efi wiring harnesses for older cars... If it turns out to be a wiring issue thats really widespread, that might be an option, although you could likely go with a ms3pro setup at that price.

If its just a connector reliability issue, the USAF figured out how to (usually) prevent aircraft from falling out of the sky long ago... https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKE wi1_uC7nvDqAhUKTKwKHUVpB-YQFjAKegQIARAB&url=https%3A%2F%2Fwww.corrosion-protect.com%2Fwp-content%2Fuploads%2F2018%2F07%2FScott_Dobson.pdf&u sg=AOvVaw3-OXqiWs5rJpsAQyiNa1Zk

The Navy stuff works just as well for ~$12 a can, vs $80 for the supercorr-A the USAF and aircraft manufacturers prefer.

Carbs are a pain too. I have a set of 46s on the 2.8RSR rally car that are all gummed up with crappy California fuel. That is the next car to make it into the garage! :)

-Wayne

In the previous pages, I documented how I went through and have performed multiple smoke tests, checked the harnesses, etc. There aren't too many things to go over on this. Injectors and perhaps a chain tensioner are the only thing that I can think of (and pretty much everyone else I've talked with). This one is a strange one...

-Wayne

I still suggest getting a wideband 02 unit... otherwise you are still troubleshooting in a cave with a dead flashlight...

14point7.com has a somewhat pricey but excellent unit with extensive datalogging ability for afr. ignition and a few additional sensors. Comes with the logging software.

I suggest reading this thread before you post.

Thanks for the suggestion, which is good. Indeed, since day one I have had the LM-1 wide band monitor plugged into the car and have been recording all of the values.

-Wayne

Great, so when the idle starts "flubbing" at 1 minute, what happens to the afr?
Any ability log ignition timing as well?

I forgot about this thread ages ago, I'll go back and read 475 posts, maybe tomorrow.

It's detailed in the previous threads. There is a mismatch between left and right AFR - one lean and one normal / rich. This has been the crux of the confusion...

-Wayne

ok, caught up a bit through the first month... Think I confused this for a long ago efi thread.
You have a ton of good help here, so I'm going to suggest a couple more ideas and check back in in a month...

Have you tried installing the lm2 and using its fake narrowband output to feed the ecus 02 input?
it will then regulate "stoich" to 12.5:1 or whatever value you desire. This would likely largely fix a good part of your drivability issues.

Your basic problem is essentially what the fake nb output is designed to fix, although you would be actually working around the actual issue... one analog that comes to mind is adding series resistance "ballast resistor" to the cht circuit on djet to drive it a bit richer.

The side to side delta is weird, and could very well be cam timing, but sensor placement and temp matter a lot, The top end 14point7.com wideband controllers can read back/log sensor temperature... They all read back the temp (thats how they control the heaters) but Alans units actually have that info logable, depending on the model.