3.2 stumble when cold

[dv88carrera]

I drive an 88 3.2 carrera which is stock with exception to a stainless exhaust, K&N intake, and chip. All was installed prior to my taking ownership of the car.
Car starts and runs strong, but is very sensitive to warm-up time. For the first 5 minutes/2-3 miles of driving, it wants to stumble/bog just when you let off the clutch in first gear (as though there is no cold-start enrichening). Fuel economy is not good either, I'd estimate it is 12-15 mpg city (mostly due to a heavy foot).
Was going to start w/basic tune-up (plugs/wires/rotor/cap/valve adjustment/filters) before going too crazy w/troubleshooting. Wanted to ask if anyone has seen similar problems with a chipped 3.2. Does this seem normal?? For a 3.2 with 147K, it pulls like hell from 3-6,000 RPM, and thought the chip may have caused the bottom end to suffer. But this problem is only really noticable when cold.
I'm a aircooled VW guy, who is new to the 911 scene, so any help form this forum would be appreciated.!

[MASSA]

Wish i could help you. I have the same problem. Kind of randomly occurs though. I have no chip but i do have the cat removed and K&N cone setup...

I hope someone can help. Porsches shouldn't do this!

[Bill Verburg]

Just a guess, O₂ sensor?

I have the exact same problem with my 1984 3.2 without chip. Just when you let off the clutch in first gear it almost stalls. Only happens when the engine is cold or almost cold. Never when at normal operating temp. Quite annoying since I have to work the clutch much more than otherwise necessary (shortens clutch life).

Could a worn air mass meter cause this kind of behaviour?

[dv88carrera]

Mikkel-

You are exactly right....I have to feather the clutch as well to overcome it, fine once warm.

[goat]

As an owner of a 1988 911 with SW chip I have none of those problems.
Idle does hunt a little when cold but never close to stalling. Its usually a little high.
do your basic tune-up (plugs/wires/rotor/cap/valve adjustment/filters
O2 sensor replacement would be good too.like bill said.

[NOH20]

Just a guess but check out your ambient air valve. The AAV is located in the engine bay on the passenger side. It is up by the oil filter and looks like a mushroom.

The AAV helps the engine idle when cold. It has a couple of vacuum lines attached to it, one of which leads back to the throttle body.

[stlrj]

My 86 3.2 had the same problem with the stock chip. Turns out the mixture was too rich which caused the bog and easy clutch/stall when cold.

Night and day difference now that it's leaned out with lots of bottom end snap.

Cheers,

Joe Garcia
Redwood PCA since 1976
74 w/ 86 3.2

[dv88carrera]

Joe-

How did you lean it out?

[stlrj]

There's a lot of info on the CO adjustment on the air flow meter when you do a search.

On our 3.2's it's a real PIA since you have to remove the air flow meter to drill out the anti-tamper plug that covers the mixture adjustment screw and remove the plastic cover to add more spring tension just to get the mixture right...too many places for the average Pelican stop in his tracks or mess up.

Try to find a wrench to do this for you and he'll think you lost your lug nuts!


Compare that to the one screw adjustment on the AFM on the 3.0 SC engine and you'll understand why so many 3.2's are so sluggish on the bottom end and why SC's are so much fun to drive.

Joe

[livi]

I experience that idendical fenomena on my stock Carerra 85. Lasts no longer than a couple of minutes. Only a problem when backing out of the garage. Thought it normal...

Markus
Carerra 85

[MASSA]

I've tried all the suggestions in the past except the AAV. Same issue. sometimes i'll hear a loud clunk, then the problem goes away. (Almost like a throttle plate or air flow plate opens up...) Once she clunks, theres no feathering required. the only thing i changed was removal of the stock cat. Could the loss of back pressure during warm up have some effect? Everyone else has a cat?

[stlrj]

Mine has a cat and it runs just fine.

[TheMentat]

For what it's worth, I have the exact same issue... no cat w/ aftermarket muffler (euro-spec car). It requires feathering from stone cold, but is fine after about 2 minutes. I also thought it was normal.

[Sonic dB]

Cylinder head temp sensor going bad?

[strupgolf]

Boy, I have the same issues. I think Ill change out the c0 sensor first, then my mechanic says the cylinder head sensor could be the problem. Iknow its running rich, but I dont want to try that, sounds like I could screw it up more. Also, my cat is gone too. Hell, I stripped the nut on the oil drain the first time, so WTH.

[stlrj]

I doubt that replacing the 02 or head temp sensor plus the cost of labor is going to solve this over rich tip-in bog situation when the rich signal is coming from the air flow meter.

The same situation on a CIS engine would be solved with a simple turn of the hex CO adjustment screw on the air flow meter, so why not treat the DME engine the same for the same symptoms?

strupgolf, your 86 3.2 already has the upgraded two wire head temp sensor, so replacing it would be a great waste of time and money.

We tweek everthing else so why is everyone so afraid of touching the DME air fow meter?


Cheers,

Joe

[TheMentat]

further to stlrj's comments... According to the Bentley manual, when diagnosong cold start isues, one can rule out the O2 sensor, since the DME does not even use it until the engine has warmed.

[yelcab1]

I had that when I had my 84. It was loose hose clamps on the vaccum lines some place.

You could always look at the O2 sensor and the idle valve.

[ausgezeichnet]

I have the same problem on my 84. I think it may have to do with the mixture. I have already re paced the 02 and CHT sensors, and made the AFM mods. The Only thing I have not done is get the air/fuel mixture analyzed or set yet. That's next.