CVR_Rally

Hi all,
I am running out of ideas on what could be the source of a rough running, missing, 944S. I recorded the sound from the muffler with my iPhone so you can hear how uneven it is including two pops.

https://soundcloud.com/christopher-c...e/944s/s-6YNR1

I have done:
Plugs, Coil, HALL sender, and the DME temp sensor. The cap/rotor are next but I haven't seen any arcing. The also looked in very good shape but before I throw more money at it just wanted to see if others might have some insight.

Fuel pressure is good and it passes the leak down test. Should I be chasing vacuum or really am what I am experiencing is bad injectors?

Thanks,
Chris

V2Rocket

thats a good microphone..
what speed is the engine idling at?

bonus12

I suppose it could be a dirty injector or maybe just a dirty air filter. Have you checked these? Do you know what cylinder it's coming from? Sounds like a misfire to me.

CVR_Rally

It is about 950.

CVR_Rally

It runs like this with the filter on or off and it looks fairly clean besides. However, I did not remove the injectors so that's an unknown. As far as to which cylinder that's also an unknown. Now that I've run it a few times I'll pull the plugs to see if one looks dirty.

I have one clue I just remembered. When I first got the car #4 plug was pretty wet maybe even oily? almost like it was never firing. I figured bad plugs. If I pull them and #4 is different from 1-3 then I'll chase that one specifically.

I'll also go on the hunt for a vacuum leak. Clarke's Garage says to pressurize the intake manifold and listen for leaks. I tried this once but didn't really hear much. I removed the vacuum line from the Fuel damper while running and it had good vacuum so I am thinking that's not it.

Chris

EDIT:
I checking this morning with my old timing light and each wire is working and the cap is solid (no cracks). It even runs a little better cold. The idle does hunt a little (just barely) . I pulled the small vacuum line off the Brake Booster and there was no change to the engine. When I get a chance to pull the plugs maybe I am chasing a vac leak.

931guru

Bad spark plug wire. Do a resistance check, and three will be right and one will be open.

konakat

Sounds similar to this thread. https://rennlist.com/forums/924-931-...ntil-warm.html

Check that the screws securing the rotor are tight.

CVR_Rally

I ordered a new cap. The rotor is nice and tight but who knows...could still be a weak spark.