Dear rennlisters, I’m a brand new member. I have used this forum as well pelican over the last two years owning my 944 as great resources for help with my car.

Unfortunately I’ve come across a spectacularly difficult issue that’s got multiple specialists in multiple states stumped. So here I am pleading for wisdom.

’83 944 has been my daily driver over the last two years. That being said easy going miles. I lived about 2 miles away from school the first year I bought it. Last year was spent driving no more than 20 miles daily round trip for about 5 months out of the year.

Its been running peachy up until one day I go to pick my brother up from school only to have the car crank endlessly and not start. Completely out of the blue. Had driven him to school in it earlier that morning without fault.

Pulled apart the airbox (found a puddle of oil) cleaned out the filter the box the AFM and the throttle body as well as threw in a fresh set of plugs. Managed to get the car running. It ran terribly and filled my garage with exhaust fumes and smoke.

From then on the car would intermittently stall, refuse to start, or run like complete crap and throw black smoke out of the pipe. Put in a new battery, didn’t help. Completely removed the intake cleaned and inspected, saw nothing out of the ordinary and didn’t help. Replaced the JBoot and still to no help.

had the car towed to my local shop. Owner has owned a fair number of 911s 924s and 944s. He couldn’t figure it out.

Had the car car towed again to my dealer who is now a Porsche Classic partner. Tech daily drives one and has worked on them since the rolled off the factory line in 82.

Paid 600 bucks for them to change my oil because fuel had diluted the oil, they still couldn’t figure it out. It is worth noting after the oil change the car ran excelellent for about two days.

Now 6 months after this started happening the issue hasn’t been solved. I’m at my wits end.

When the car doesn’t start it does crank healthy. Just won’t fire. But for some reason if I pull the fuel pump fuse, (number 2 on the top panel as labeled in the owners manual) the car will eventually fire up. Sometimes it dies right away, sometimes it idles very very rough, sometimes it idles completely perfectly WITHOUT the fuse in. It will idle anywhere from 30 seconds to as long as 5 minutes without that fuse. If I try replacing the fuse the car dies immediately. It’s my understanding that the car shouldn’t even run without that fuse so how this is happening is beyond me.

Sometimes if I replace the fuse the car manages to idle at about 3 or maybe 400 rpm. If I run up and disconnect the AFM before it stalls, the idle jumps to a perfect 900 rpm and the car runs great. No idea how that’s possible. I tried disconnecting the temp sensor once as well when it was throwing a rough idle fit and it did the same exact thing. Jumped right up to 900 and ran smooth.

I have spark, and I have fuel. My DME Relay is about a year old. There is no gas dripping from my vacuum lines to the FPR.

Im terribly sorry for the mountain of text I’m trying to be as detailed as possible. Any help would be greatly appreciated. Thanks all!

Regards,
Jake

It was a little extra because I gave them extra hours to try and diagnose it. They couldn’t solve it so I opted to just bring the car back home.

If that sensor is only 20 bucks I’ll look into replacing it. The problem doesn’t seem to be temperature related. I almost wish it was it would be a lot easier to diagnose. I’ll also have to hunt down a known good AFM.

I will defintaley let you guys know if this thing gets solved. Every single thread I found with issues remotely close to mine never had a solution posted!

Thanks for the replies!

Jake

Quick update, brand new temp sensor, car started up and idled at about 200 rpm. Managed to run up and disconnect the AFM. Idled a little higher (maybe 700) before smoothing out at 900. As soon as I plugged in the AFM to the harness the car stalled. If it does help I did test the AFM per Clark’s garage and it is operating normally. O2 sensor checks out as well. And TPS. There’s another puddle of oil in my airbox again. I imagine that’s from the last time I let the car run. I got it running earlier today for the first time in about 2 and a half weeks. Took some time but she smoothed out and idled okay on her own normally. Moved it to the street, gave it gas (up to 2k rpm) then sputtering and low idle. Disconnected the AFM and sure enough jumps up to 900. Let the fans cycle once and then she died out of nowhere.

Noted about cylinder washing. Part of the reason I let the car sit over the last few weeks (been trying to preserve that fresh oil) though it’s already starting to smell like gas.

Also aware of the differences of the pre 85.5 and later cars AFM DME comparability. Once upon a time I was going to do this mod anyways just to get rid of that fuel cutoff after letting off the throttle and maybe start playing with chips. Decided to keep the car as stock as possible nearly everything is completely original.

Running the pump out of the tank is a very interesting idea I will have to give that a try if all else fails. Thanks for the insight so far everyone!

Was a fuel pressure leak down test performed? Is there fuel smell in the pressure regulator control line!

Since it idled normally with afm disconnected (900rpm), I would continue there. It may ‘test’ normal but I thought those voltmeter tests were prone to errors? You haven’t played with the CO screw in the afm, have you?

I would be concerned that after cleaning the puddle of oil in your intake, it puddled up so quickly again. It is likely your AOS seals are badly worn causing a bad fuel/air mixture and all sorts of non starting issues due to the excessive oil fumes in the intake. I would take the intake off, clean everything including the throttle, AFM, airbox and intake, and replace the AOS seals.

The guys at the dealer did adjust my CO levels. I never messed with that screw prior to taking it in. It did not solve the problem however. They did a pressure test and said that the fuel pressure was normal.

As soon as I can get my hands on an AFM I’ll swap em out and see what that does.

There is an odor of fuel in the vacuum like to the regulator, when the car was running I pulled the vacuum line and waited to see if gas would spill out of the regulator indicating a ruptured diaphragm but it’s dry every time I try it. Had it off for over 5 minutes yesterday and no gas. The line on the underside of the regulator is leaking however. It’s on my to do list along with AOS seals now.

Again when the car idled poorly before i did remove the temp sensor as well and the idle returned to normal. It is also worth noting that I did check timing on the cam gear, balance pully, and flywheel marks and they are all spot on.

Speaking of over filling the oil, I’m wondering if happening is due to the gas filling the oil level so much it’s gettinv blown back up through the intake and pooling up. It looks like those seals are only a few dollars so I’ll see how quickly I can get my hands on em. I’ve had this intake on and off now so much I can have it disassembled and reassembled within 20 minutes.

Ill contact my local Porsche recycled parts guys see what they can do for me. Thanks again for all the help! Keep those ideas rolling.