Troubleshooting Poor Cold Start on a 3.2

[mysocal911]

Originally Posted by et cetera

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

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

[et cetera]

Originally Posted by mysocal911

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.

[mysocal911]

Originally Posted by et cetera

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?

[et cetera]

Originally Posted by mysocal911

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

Correct

[boyt911sc]

Originally Posted by et cetera

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.

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

Tony

[mysocal911]

Originally Posted by et cetera

This issue has been driving me a bit crazy and has me running in circles. Rather than continue to throw $100 at it each time I blindly replace a part I wanted to get a few other opinions before my next step.

Symptoms:

• Starts when cold and immediately dies
• When running it has short power cuts during hard acceleration
• Wants to die when taking off from first gear, need to give it plenty of throttle to get going or it will die
• The idle is just over 1100k RPMs and does tend to "bounce"
• Occasionally, when I go to turn the car over the key feels manually locked out of the start position. After taking the key out and trying again it works after a few times.

Other Facts:

• If I give it a little gas while starting it will eventually find an idle and warm up.
• While its idling, and still cold, if I even look at the throttle to soon it dies.
• It warm starts just fine.
• Separately, I can jump the CHT at the female connector and it fires right up and idles at 800 RPMs. It does run a little rich in this situation as indicated by small amounts of white smoke.

What I've done so far:

• I purchased this motor rebuilt by a previous owner, many items were replaced with new, specifically the fuel injectors had been cleaned and the fuel lines refreshed.
• All new Plugs, Cap and Rotor, fuel filter(No Change)
• Cleaned and bench tested the ICV (No Change)
• Replaced the Idle Control Microswitch (No Change)
• Replaced the Cylinder Head Temp Sensor (No Change)
• Swapped in a known working Coil (No Change)
• Fixed a minor vacuum leak at back of Throttle Body (No Change)

... and thats where I'm at today. I have a friend who is going to let me plug in my DME into their working car to rule that out, but I'm not sure where to look next.

I read through a bunch of threads on the various subjects. Based on those I am looking into a few other items, but I'm not convinced they are the issue.

DME Relay - I get power to the fuel pump. My understanding is it wouldn't even start if this was the issue, but I may be wrong.

Crank Position Sensors - They are gapped correctly. I do have an over the transmission oil line from ER that runs near them, not sure if that could cause problems. My understanding with these is also that the car wouldnt start at all if they had failed.

Throttle Position Sensor - This would explain the hesitation under power, but I dont believe it would impact the cold start and idle.

Anyhow, I think thats everything I've done to this point. I'd love to hear your thoughts or just some words of encouragement so I don't give up.

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?

[et cetera]

Originally Posted by mysocal911

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.

[mysocal911]

Originally Posted by et cetera

Yep, I checked those before as you instructed.

Pin 5 was properly grounded.
Port 13 read 1.67v

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

Originally Posted by et cetera

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

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?

Originally Posted by et cetera

Separately, I can jump the CHT at the female connector and it fires right up and idles at 800 RPMs. It does run a little rich in this situation as indicated by small amounts of white smoke.

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

[et cetera]

Originally Posted by mysocal911

[B]

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.

[911obgyn]

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

[mysocal911]

Originally Posted by et cetera

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.

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!

[et cetera]

Originally Posted by mysocal911

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.

[wazzz]

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.

[et cetera]

Originally Posted by mysocal911

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!

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.

[mysocal911]

Originally Posted by et cetera

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, Bench testing Carrera Idle Control Valve

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.

[et cetera]

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.

[mysocal911]

Originally Posted by et cetera

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;



"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.

[proporsche]

Originally Posted by et cetera

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.

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

Ivan

here

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

[et cetera]

Originally Posted by proporsche

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.

[mysocal911]

Originally Posted by et cetera

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?
Bench testing Carrera Idle Control Valve