Next check the fuel pressure and the vacuum lines going to the regulator & dampener for leaking fuel.

The fuel pressure had tested in range, but I could smell fuel in the vacuum line connected to the regulator. It was never wet, just a slight fuel smell. I went ahead and replaced the regulator anyway. None of the symptoms changed.

And you checked the vacuum line to the fuel dampener for leaks?

Correct

What were the fuel pressure values of the old FPR with and without vacuum? How about the new FPR? Thanks.

Tony

So, the engine has never run properly since you received the "rebuilt". This is significant!
Since the injectors were sent out and "cleaned", you really don't know the real state of the injectors, e.g. are they even the correct ones.
Hopefully, they are the low impedance (1-2 ohms) injectors. Obviously, the wrong injectors will cause problems like you're having.
Have you measured the temp sensor at the DME ECM connector, i.e. pins 13 & 5?

Yep, I checked those before as you instructed.

Pin 5 was properly grounded.
Port 13 read 1.67v

I bought it from reputable users on these forums. I have no reason to believe they are anything but reconditioned OEM injectors.

When warm, the temp voltage should be less than .50V.

Did they ever run the engine? There's basically nothing else except the DME ECM.
Did they supply the ECM? If not where did it come from?

If the temporary fix is that simple, it usually indicates the wrong injectors or the ECM, assuming all your other tests were done correctly.

The motor had been run, and tuned. To my knowledge it’s the same ECM that the car was tuned on.

I can check the warm output for the CHT sensor, but I really don’t think it’s that as my issue is primarily with the cold start.

To try and be more specific. The problem seems to be that the car starts and can’t “catch” the idle as it drops down. So it immediately dies. Occasionally it gets close, and will fire a few extra times before dying.

That would lead me to the idle switch, but I have two of them which both test fine. I did test the EMC on another car but who knows, maybe I just got lucky when plugging it in that car.

I’m gonna do another vacuum test in the morning to see if that returns anything.

I had the same issues with 85 3.2 spent a day chasing cold start and idle issues, got an innovate wide band 02 gauge and spent another day, used the 02 sensor in the bung disconnected the narrow band and tuned idle CO with AFM bypased according to bently manual, finally got CO and idle set, no vacuum leaks fixed and still had some cold start issues til i ran the heck out of it, drove like a maniac and it settled down and runs like a champ now. I dont let it set for a week and it starts and runs great. If i let it sit for 2 weeks cold start issues until i get it warmed up and run for an hour. 200K or more on the motor. Needs valve job but still CA smogs

So if that's the main problem, and you can prevent it from dying by opening the throttle. Then it's a simple idle problem
unrelated to a rich fuel mixture. But you mentioned up-thread that it will start OK if the AFM is disconnected, which doesn't
correlate with this last post.

Hopefully now the thread has converged on the real basic problem, a momentary bad start-up idle!

That’s exactly why I’m so confused. Unplugging the AFM and jumping the CHT sensor are putting the ECU in a different mode, where it runs fine. Something about the cold start mode might be off with the ECU, and maybe I just got lucky when testing in my friends car.

I want to see if I can borrow his good ECU to test on my car.

Testing your suspicious ECU on a good car is OK, but not the other way around, as a good ECU could be damaged by a suspicious car. A shorted ICV, for instance, can kill an output transistor inside the good ECU of your friend.

To be even more specific. I just started the car and kept my foot on the gas. I need to do that for a solid minute for the car to warm up. If I take my foot off the gas too soon it dies. I try to keep it at 2k rpms during that time, but it will bounce all around even when I’m not changing my input.

Based on the above, you have a cold start idle problem, and unrelated to the fuel mixture. The causes related to this;

1. bad idle valve (you indicated you checked it)
2. bad idle switch, connections, or not positioned correctly
3. bad idle valve drivers in the ECM

You should test the idle valve using this procedure;

Idle Valve Testing, post #20, http://forums.pelicanparts.com/porsche-911-technical-forum/360766-bench-testing-carrera-idle-control-valve.html

Additionally as a simple test, you can open (CCW) the idle screw on the throttle body at least 8-10 turns. This should reduce or eliminate your having to press the throttle pedal.

I reached out to the person I purchased the motor from, turns out the DME is not the one that originally came with the motor but one that had been in another car of his. So the custom chip in there wasn’t for this motor.

I’m gonna start by trying to reset the idle. I’m also going to try and source a stock chip.

Found these sources;

http://forums.pelicanparts.com/uploa...1714256367.jpg

"Reseting the idle" is ONLY used when the idle is within 50-100 RPMs of the desired idle per the Porsche spec. It's NOT the major source of your problem.
If the engine idles OK when it's warm, then idle doesn't need to be "reset". Remember, once the engine is warm, the idle valve is only used to stabilize the
idle for load variations, e.g. A/C, lights, etc. It can also prevent idle undershoot on engine decel.

you know there is an adjustment on your DME for fuel quality.....

Ivan

here

https://www.911chips.com/fuelsys.html

Took a look at this today. Found it was in position 5. Turned it back to 0 but it didn’t have any effect.

It has a very minor effect on the fuel mixture.

If the idle valve system is functioning properly, it should have the same effect as your pressing on the throttle pedal at startup to keep the engine running.
Did you do the the valve test on post #20 here?
http://forums.pelicanparts.com/porsche-911-technical-forum/360766-bench-testing-carrera-idle-control-valve.html

I think I may have solved it! I had a buddy come by to give me another set of eyes and a clear mind.

First we jumped the CHT sensor at the connector to warm it up. Then once it was warm we pulled the jumper to see what would happen. When I did, it died as expected.

Next I jumped it again and unplugged the AFM. It started running very poorly.

Then I plugged everything back in and started it, it started up well and idled a bit high at 1100 RPM. But, if I started to press the throttle in I could see that as soon as the idle switch disconnected the car would die. I did my best to make sure the switch had as little play as possible before the throttle started to open. This seemed to help a bit but it would still flood and die.

Since I was unplugging other sensors we decided to unplug the WOT sensor and try starting it. All of a sudden it idled better and I could disconnect the idle switch and it wouldn’t die.

So, I took the cover off the WOT and could clearly see it was making a connection even when the car was at idle. Someone had definitely messed with it and bent the upper arm so that it was in contact at all times.

My buddy gently bent the arm back and we dialed it in so it would only come on at full throttle. We revved it a few times, and every thing continued to work great. We buttoned everything up and took it out for a drive.

The bucking out of first gear was gone, it no longer had any dead spots when under throttle. It just pulled hard all the way up.

I have it in the garage now cooling down. My last test is to cold start it and hope it doesn’t die.

Great progress! The full-throttle mode ignores the AFM and uses preset fuel settings. Also, when the idle switch is closed
and the full throttle switch is grounded, the DME ECM goes into the idle setting mode, which prevents idle valve from functioning.
You need the idle switch to function or you'll have a very low idle (or no idle) with a cold engine.

The key problem, related to full throttle switch, would have been determined sooner by using the recommended ICV test procedure
in post #55. The ICV test would have indicated that the ICV was non-functional, because it was in the idle setup mode with the full
throttle switch at ground with the idle switch.

To bring some closure to the thread. The car now starts well when cold.

I would be surprised to see others have the same issue I did, as the Full Throttle sensor had to have been bent to be in contact at all times. Hopefully all of the troubleshooting info in the thread will help someone find their problem faster.

I do still want to properly tune the car to ensure its running in top shape.

The one thing I would be curious to know is why would someone modify the Full Throttle sensor to be engaged at all times while simultaneously adjusting the bypass screw on the AFM to be full rich? Is there a situation where that would be beneficial? It seems to me like it would only create a situation where the motor flooded every time you started it.

Are there people out there doing this and then just developing custom tunes on their chip to compensate?

Congrats !

Yep, the OP did something to the engine i.e. adding a "cheap" fuel mod hack to make it run rich all the time, not good for the engine ... which was why I recommended reaching out to the fella for more info earlier.

Good find.

Now that you fixed the WOT switch you really need to set base idle speed to be certain it's properly set. Also double check both the idle and WOT switches are properly adjusted.

You also should invest in a decent WBO2 gauge so you can properly set your mixture.

If indeed the WOT switch was ALWAYS closed this means that at idle stop both the idle and the wot switches would be closed! If this occurs the DME enters into base idle speed calibration mode, a special mode that only normally possible for calibrating base idle speed. Both switches normally can NEVER be closed at the same time, except when you do base idle speed calibration.
in this calibration mode the ICV is parked at about 10% open and the idle speed control is turned completely off. This explains all the stalling and issues you had at idle.

Yes, as also posted in #103;