It's not a stock (original) memory chip (PAE). Who knows what effects it has? Besides, the processor chip has been replaced too. The original DME ECM didn't use a 8031 chip.

The 1st is only resolved by actual part numbers, and the 2nd by using a pressure gauge.

Now on that point I'm in complete agreement.

Needs to be measured and confirmed as already emphasized.


How did you come to the conclusion that the OP needs another DME ?

Describe your line of reasoning for our enlightenment.

Thanks

That hasn't been concluded yet. Since it's been modified, it needs to be fully tested, hopefully on another car and eliminated.
It can also be bench tested!

We are on the same page wrt testing and measuring and all the good stuff during the process of elimination. You might be right that the engine has a perfect vacuum seal but why just assume ?

Did you read the OP's post about the vacuum ports being plugged ? Would you know if that requires tweaking the ECU to compensate ?

Most lack a correct way of testing for a vacuum leak, i.e. proper equipment, so other tests should be done first. An EFI system is not like a CIS where vacuum is critical.
Besides, vacuum leaks are rare on the 911 3.2. If a vacuum leak is of concern, one can always carefully use carb cleaner to find a leak.

I’m totally with you guys. Going to be putting the ECU into a known running car tomorrow.

After that I’ll be moving on to testing the fuel system.

I appreciate all the help!

Yes, it could do, because somebody could respond to a vacuum leak with some further maladaption. It's moot, though, because I'm not taking "too rich" as gospel yet.

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For kicks, I also tried the AFM at a few different spring settings to see what would happen. There was no change. I think I can rule that out as a primary suspect.

Please, check the fuel pressure is responding to vacuum. Ever since you said engine revs don't momentarily respond to lifting the oil cap, all roads point to that. Even if there are other problems, you'll never get them fixed until you've got the fuel pressure adjustment working.

The vacuum lines smelling of fuel is a red flag for a leaking diaphragm. Try plugging them so fuel can't travel down them to the throttle body. Ideally you will have an AFR meter when you do so. See if plugging them leans out the mixture.

The modded chip probably worked fine when installed into a fully working system, else it would have been swapped back out for the original.

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Then that's a problem. The major way the injectors provide more fuel as the RPM/load changes is thru the AFM. Small changes in the AFM voltages result in significant changes to the AFRs.
You need to try to understand how an EFI engine operates.

NOT GOOD!

Remember, vacuum lines lead to the intake manifold which smells like fuel.
Fuel actually in the vacuum line is a problem.

911 3.2 ('84-'89) Basic Troubleshooting A Running Problem

1. With Key-Off - DME ECM disconnected
a. check for ground on pins; 2, 5, 16, 17, 19
b. check for ground on pin 3 with throttle at full open

2. With Key-On and engine not running and cold - DME ECM connected
a. check for 12V on pins; 1, 14, 15, 18, 20, 35
b. check for about 5V on pin 9
c. check AFM input pin 7 for about .80V to 4.7V, idle to throttle at full open
d. check O2 input pin 24 for about .50V
e. check temp sensor input pin 13 for greater than 1.5V

3. With engine running and warm at idle;
a. check fuel pressure; 30-35 psi (DME relay output pin 20 < 1.5V)
b. check AFM pin 7 for about .80V to 1.2V
c. check temp sensor pin 13 for less than 1.0V
d. check pin 24 (O2 sensor input) for a varying signal (.30 - .80 volts)

Note: All test points are on the DME ECM 35 pin connector, back-probing with the connector shell
removed or with a breakout box.

Went over to my buddies house today and tested out both my ECU and Relay on his car. Everything worked perfectly fine. Looks like I can rule those two out.

I do still want to check the fuel pressure, but I’m still a bit suspicious of the ICV. I know it worked when I bench tested it, It opened and closes when I apply a 9v battery to it, but I don’t suspect it was returning to a neutral position.

Read post #20 here; http://forums.pelicanparts.com/porsche-911-technical-forum/360766-bench-testing-carrera-idle-control-valve.html

Of all of the problems you state in post #1, only one relates to a ICV;

Next, you need to follow post #53 above, key tests which you haven't done, or maybe it's time to visit a good Porsche repair shop.

1: With Key Off
a. all ground tests pass
b. Seems to be grounded at both full throttle and off throttle

1. With Key-On and engine not running and cold
a. All connections read 12v
b. pin 9, 0 reading (also checked at the AFM harness and there did not appear to be power making it to the AFM)
c. pin 7, 0 reading
d. pin 24, 0 reading
e. pin 13, 0 reading

Looks to me like there may be a wiring problem. The shop who installed the motor did the wiring, so I need to research where power should be coming from for the AFM.

Great that you did the testing! We have good data now:

1. You're missing the ECU AFM power 9 output. Without this, there's no output on pin 7 to the ECU and no fuel mixture data. It's the KEY input to the ECU for proper running.
2. Pin 24 is the O2 sensor input. You may have a Euro ECU w/o O2.
3. Pin 13 is the temp sensor input. If pin 13 reads zero volts when the sensor is disconnected, then it's shorted to ground. This will make cold starting very difficult.

Nice work.

I was thinking a bit more about this.

1. Does power for the AFM come from the ECU? If so, my test would read zero because the tests were performed at the ECU harness connector. I want to connect the harness the ECU and test for power at the AFM connector.

3. For the CHT should I also be testing for ohms or just voltage?

Correct.

Voltage when connected.

What would be the best way to check the voltage for the CHT when its plugged in? Open up the ECU and check from there or at the plug connector in the engine bay?

If you disconnect the CHT from plug connector in the engine bay and measure voltage on connector from ECM harness, you should read about 4.3 volts.

No! Do as Wazzz said, and try to back-probe it when plugged in at the sensor. Since you don't have a break-out box, you really need to remove the ECU connector shell and back-probe the ECU connector.

I plugged in the ECU and checked power at the connector for the AMF, voltage read 4.95.

I then checked the connector for the CHT and it read 1.88.

Figured out how to get the back off the ECU connector.

Port 13 read 1.67
Port 7 read .20 at closed and 3.65 at fully open. Voltage progresses smoothly as the barn door was opened
Port 24 read 0

I purchased a smoke tester just to double check the vacuum lines, figure it wont hurt and its a good tool to have around. Should get here later today.

I'm also going to find some time to go rent a fuel pressure gauge so I can check that off the list this week.

To add a bit more context here. I had this 3.2 put into my car after the original 3.0 spun a rod bearing. The metal in the oil system meant that we replaced everything, including the oil tank. The oil tank is the screw on cap style so we also needed to put on a new oil cap.

I performed the smoke test on the vacuum system just now and guess where smoke was pouring out of… that’s right the oil cap. The new oil cap was never installed with the proper gasket. I’m ordering one now and hopefully that will be the last of my problems.

I just want to extend a huge thank you to everyone who gave me pointers. I was pretty familiar with the CIS systems, and I’m happy to have gotten a quick education on the motronic setup. At least now I know what the common issues are and how to troubleshoot them in the future.

Hopefully this thread will help others find answers in the future.

glad you got it fixed..but..for the future readers
It would help to add all what you did to your 911 to help you solve the problem
As in this case -new oil tank and missing o ring in the cap...;-)

Ivan

Yes, it was that simple!

Well, I guess I was wrong. Put it all back together and now it won’t even fire up.

I used a little starter fluid and it kicked on for a second, so it’s getting spark.

Is it possible that the smoke test exacerbated a problem with the fuel regulators and they’re now completely choking off fuel?

Sorry I fell off the map. I went on vacation then immediately on a work trip and didn’t have a chance to get back to the car.

I found a loose wire at the fuse panel which got the fuel pump going again. I must have knocked it loose when checking the fuses.

I’ve replaced the fuel regulator because I had a new one. Tested the fuel pressures and they were in the expected range.

I still can’t get the car to cold start without keeping my foot on the gas.

It will start and idle fine when I unplug the Cylinder Head Temp sensor and jump the female connector going back to the ECU. What I haven’t been able to find an answer on is what type of a condition this puts the ECU into, does it make it run more rich or lean with that connector jumped?

I think somewhere up above I suggested that you get a Air Fuel Ratio meter. That suggestion still stands.

Not trying to be rude, but in Air Fuel Ratio meter isn’t useful when the car won’t start without forcing it into a different condition.

I did find this video on YouTube. https://youtu.be/kcTkFjOt8Kc?si=eIeHL_O3k1vrgwzP

He has the surging idle, and after he “repairs” the ICV he ends up with the same start issue I’m facing. In the end replacing the ICV seems to fix the issue.

I did the common tests for the ICV, but I suspect something is different when it’s actually running in the car. I’m just gonna order an aftermarket one to rule it out.

Leaner. It tricks the ECU into "thinking" the engine is dead warm, so it leans the mixture.
Open circuit is the opposite, tricks the ECU into thinking the engine is dead cold, so it makes it run richer.

Replaced the ICV, no impact.

I feel like I’m beating my head against a wall now. Not sure what direction to go next.

I think I’m gonna do another smoke test.

I was curious to see where the bypass screw on the AFM was set to, and it seems to be tightened all the way down. I believe this will cause it to run on the rich side.

I turned it out a full 5 turns, but it doesn’t seem to have any impact. The car still fires and dies immediately.

I know I need some other tools to properly set the AFR, but how far can I back that screw out to try and lean out the mixture?

The mixture screw ONLY affects the idle mixture, i.e. once the throttle opens it has no effect.

I just unplugged the AFM and started the car. Fired up and idled perfectly. There’s gotta be something off with the settings on the AFM, right?

Sounds like it. The AFM rarely fails, though. Hopefully the flap doesn't stick or the spring setting isn't wrong. Have you check the temp sensor cold resistance?
That's more likely the problem.

I did check the temp sensor. The original one was in range, but I bought a new one anyway.

Tested the new one to ensure it was in range and it checked out as well.

I’m starting to worry the AFM was really messed with before.

Jump the temp sensor with a paperclip without disconnecting the AFM.

I have, starts right up and idles. Anything I do that leans out the mix at start seems to have a positive impact.