Generally rough running

[911 dreamer]

I have this issue where the car starts and idles fine but when cold, I drive down the road at a steady 30 out 40mph, the revs fluctuate by about 500 rpm, enough to hear and enough to feel. When warmed up fully it's fine, until the next day when it does it all again. The only other issue is noisy tappets on cold start, for the first minute or so, then the tapping goes away. Is there any chance the two could be linked? Any thoughts?

 

Thank you.

[Loren]

Exact model and year of the car please?

[911 dreamer]

Carrera 2, 1998, 3.4, just over 100k with a new ims 6k ago..

[Loren]

Likely time to clean the cold start valve (ICV) and throttle body.

This has been covered here many times so please search.

[911 dreamer]

Sorry I should have said, throttle body was replaced already, along with maf. Where is the cold start valve please?

[911 dreamer]

2 hours ago, 911 dreamer said:

Sorry I should have said, throttle body was replaced already, along with maf. Where is the cold start valve please?

Got it, the ICV has been done too..

[Loren]

If those are new and the correct parts then you have an intake air leak.

Use a smoke machine to check for air leaks.

[911 dreamer]

Thanks Loren, not sure where to get a smoke machine from just yet but I'll try this and let you know. Thank you.

[Loren]

2 hours ago, 911 dreamer said:

Thanks Loren, not sure where to get a smoke machine from just yet but I'll try this and let you know. Thank you.

 

Most good auto repair shops have them.

[JFP in PA]

5 hours ago, 911 dreamer said:

Thanks Loren, not sure where to get a smoke machine from just yet but I'll try this and let you know. Thank you.

 

A good smoke test unit is upwards of $1.5K, so I would consider doing what Loren says and take it to a shop with one.

 

[911 dreamer]

Thanks guys appreciate your help