Runs REALLY rough for first 30 mins...

[Pauwl]

Posting while enjoying what I though would be a nice warm break in Southern California. Just been to SeaWorld with the kids & seen more water (in the form of rain) than the resident Orca!

Anyway: waiting back in France is my '84 928S (Euro) that starts REALLY rough. I sometimes even need to touch the accelerator. Once started, it sounds like it's running on 3 cylinders - that rough.
When it does this (each start from cold) - it shudders if you try to accelerate anything other than really slowly. At some point it feels like more cylinders kick in, but don't try to accelerate fast even then.

After about 30 minutes, all is well - acceleration just as I am used to.
After a stop then start again an hour later all is fine. If I use the car every day it stays fine. Leave it for 2 days or have a night that is too cold, and it starts again.

Where should I look first?

regards,

Pauwl

[Danglerb]

Two thoughts;

Rough on cold starts initially makes me think fuel mixture isn't rich enough.

BUT

30 minutes is much longer than it should take to be fully warmed up.

Makes me think temperature related, but not directly, more like something sticks when cold, and even after warming up needs more time before working correctly. Unfortunately nothing comes to mind to check first, as it could be so many things.

Moisture condensing on some wire, sticky control valve, bad temperature sensors.

Start with the basics, while its in the rough running condition verify fuel, spark, and I don't see how it would be related, but compression for completeness. Fuel mixture and spark timing or misfires seem most likely.

*** Are you taking back a suitcase full of 928Intl 1/2 price used parts?

[Landseer]

Buy a time/temp sensor from 928's International before you go back and try that.

It has a tremendous effect on cold start / operation.

Its a simple installation (screws into the water bridge, is easy to access (at least on non-Euro).

[Pauwl]

Thanks guys. Just had a look on their website, and see several temp sensors.

Landseer, any idea of a part-number or a way to identify the one you're talking about?

Danglerb, out here with the kids - visiting my brother, so probably going back loaded with toys for them - not for me :-(

Next time I'll bring the shark.

[Landseer]

Ask 928 intl for the time/temp sensor for the 84 Euro and they will know the part number from your description, that's the fastest way.

[porken]

'84 euros are digital, LH2.2/EZF, the same as 85-86 32V, but without automatic idle speed control, or O2 sensor.

It sounds like a Temp II (coolant) sensor. For LH injection, there are two sensors in one, one for the LH, and one for the EZF, so each terminal is measured to ground. (You can't use one from a L-Jet, which has only one sensor inside.)

Could also be vacuum leak(s), and the cold start bypass valve (euro LH only, similar to L-Jet) may not be opening enough.