PerceptionProblem

So, a few days ago my 85.5 N/A 944 started to misfire as well as the occasional backfire. Car is all stock except for a K & N filter. Tonight I seafoamed through a vac line and while I only used a quarter of the bottle, I filled up the whole block with smoke! (expected, this is not my first picnic with that red and white bottle)

After running the seafoam all the way out of the system, I noticed a rough idle. VERY rough. I adjusted my afm just a little bit and the rough idle went away. As did most of the misfiring.


I then noticed that when I hold the engine around 3K RPM, there is a surging and I can feel the engine gently sputter.


Should I look around for vac leaks? or maybe find myself some new plug wires and or install this msd coil I've got kicking about? Perhaps an injector is starting to die out? Maybe the Cat got itself pluggeed up, as it's the stock one? (Also, if I hollow out the cat until I can afford a new one, will that hurt the engine due to the change of backpressure?)

As always, Thank you for your help Rennlisters!!

cruise98

You have an electrical problem. I had a friend with an '84 that had the same symptoms and the speed and reference sensor connections were in very bad shape. New sensors solved the problem.

You could have fouled a plug as well. Check the wires, cap and rotor, and install new plugs. Leave the MSD coil in the box. I doubt the misfire has anything to do with the cat, but you can hollow out the cat without hurting the engine, but that is not the problem.

txhokie4life

Does the tach drop out at all? That points to either DME or CPS

I would also check the spark plug wires -- do you see any arcing? Best seen at night or in the dark.
Possibly a worn rotor -- take it off and clean the contacts.

You can also get a warn spot in your AFM, but with the misfire it feels like one of the above.

M

Kerry Chadderton

Do what I call a foundation check:

Plugs
Wires
Cap
Rotor
Fuel Filter
Air Filter
Inspect Vacuum Lines

I do these quick inspections before I start over-thinking and adjusting things. Which I'm prone to do at times.

PerceptionProblem

I got to pull my plugs last night, and let me tell you, the number one plug was FOWL! The other three weren't too bad, but that front one was kaput.

Also, she DOES NOT like the rain or driving through lots of water.

Paulyy

What happens in the rain? could be bad electrical circuits

mine loves the rain, very tail happy...

PerceptionProblem

Lots of steam, higher than normal temps and lots of misfiring. There is a shop in San Diego that specializes in 944's and I'm trying to get an appt booked in a few weeks to have someone who knows what's what give her a once over and let me know all the little things (hopefully no big things) wrong with my car.

Paulyy

you must have bad rubbers and seals. do you get water in the car?

I got water in the DME and caused missfires and a toe home.
https://rennlist.com/forums/944-turb...ded-video.html

bordin34

My car was having a similar problem of misfiring and rough idle when warm. It turns out that the steam from my bad leaky water pump was making its way into the cap and rotor and condensing.