No cold idle - A little rough and rich when warm - S4 NA
 

Hello,

sorry to bother again but I might need a few pointers concerning my non existent cold idle and the rough and rich warm idle of my S4 NA.

What it does:

No idle when cold starting. Once warmed up it gets much better and idles properly at 725 rpm but tends to stall every once in a while. Its a bit "lumpy" as expected on a ported motor. It also runs pretty rich. If I fire it up in my workshop I get tears in my eyes from the fumes after a few seconds ...

It got a brand new build street ported NA motor with lightened S5 rotors, FD housings, RX8 eshaft, ianetti ceramic seals, and RB aluminium flywheel. Everthing electronic or auxilary wise in this motor is stock. Injectors professionally cleaned by witchhunter. New seals and grommets all around the injectors too.

I checked the following:

• Re stabbed CAS (Distributor due to EU version FC). -> No timing gun available atm. timing should be pretty close however ...
• Throttle bodies are clean and no deposits on them.
• Checked for spark on all 4 wires -> Spark is there, maybe a bit weak for my taste but what do I know ...
• Replaced all vacuum lines with reinforced Gates lines. -> There were some minor leaks before, now its tight as a virgin
• Checked for vacuum leaks - non found via the brake cleaner method
• Unplugged TPS - No change
• Readjusted TPS (difficult to do because unable to warm it up due to non existent cold idle) It doesn't matter if TPS present or not. It dies right away.
• Unplugging BAC -> No change. Dies right away.

I have a spare AFM that I might try tomorrow. And I also miss my timing gun. I am confident I have set the timing as close as it gets but without timing light I cant be 100% sure.

I have heard of the coolant temp sensor behind the water pump housing or the intake air sensor able to cause problems for cold idle as well.



Your input is greatly appreciated!

Here is a picture of said car + motor:
https://cimg0.ibsrv.net/gimg/www.rx7...5949a6c224.jpg

i would start with the timing. so when you get your light, check where you are. it may be as simple as needing to be advanced some.

on a separate note, i have to say that yours is probably one of the cleanest cars i have EVER seen. period. the engine looks beautiful, too.

I just checked the timing. Had to wait for my new light to show up. After stabbing the CAS/Distributor, the timing on L1 was about 5 deg too late. So roughly 10 deg ATDC than the factory recommended 5 deg ATDC.

• I set it to about 3 or 4 deg ATDC, so sliightly advanced. Runs a bit better but not by much. Do you think I should advance it even more? I would have to do another cold start to see if the timing change actually brought some improvement.
• I went over the vacuum tubing again and looked for leaks. None found. I also re tightened the upper intake again. Just to make sure ... All set there, no changes.

Do you have any other ideas where to look for?

Thanks :) I spend quite some time cleaning and painting all of it. It makes a huge difference ...