madbrewer

I have an '83 911 3.0L Turbo look Targa , all kinds of work has been done to it within the past 1500 miles, i.e. valves, injectors, airbox, exhaust, and so on. It sits in the garage for weeks between drives, but I do try to run it to temp on the weekends. So now for my problem...

last week I started it up and it ran like CRAP. barely idling, poping, sputtering. When you push the gas it hesitates, and bogs down. If you ramp it up SLOWLY it smoothes out at about 1800 rpm. Driving, it feels sluggish and doesnt have much power even at higher rpms and it still backfires. A one way valve has been put on the airbox so at least that is safe but I'm not sure what the problem is, it ran fine on a 1000 mile drive a few weeks ago.

I was thinking fuel pump? Any thoughts or suggestions on what to check would be apreciated. Thanks.

Edgy01

I would check the fuel system. Regulator, fuel system pressure. Leaks,--air leaks going to and from the fuel regulator (near the center runner on the right side of the car). Relook the CIS box for air leaks. One of the problems with a car of this age is making sure you have covered all those issues at one time or another recently. Personally, I found fuel quality to be a big issue with the SCs. The pump could easily be an issue.

Peter Zimmermann

brewer: There is a small, silver, square relay under the passenger side seat. It's closer to the tunnel than the door threshold. It's the OXS relay and has probably failed, which will prohibit the frequency valve from running. Replace the relay, part number 821 951 253, available from your P dealer. You can probably confirm that the freq valve is not running by:
1. remove the air filter cover w/filter
2. turn on the ignition
3. gently push up on the sensor plate arm
4. listen for a loud buzz just to the left of and forward of the throttle body.
No buzz? The relay will fix the problem 99 out of 100 times.

FYI: You mention that you consider yourself "safe" because you have a pop-off valve. Don't believe that for a minute, you still must maintain the car including correct spark plug wires, CO% mixture, etc.
Pete

madbrewer

Well, I performed that test and there was most certainly a buzz. Darn, I was hoping it would be that simple, no luck. As far as fuel quality, I only use Shell Premium, it has just under 1/2 tank left over from the drive to Washington 6 weeks ago. I checked the airbox for any cracks and it is fine.

One thing I noticed was a port on the right side of the airbox with no hose attached, what is supposed to go there?

AOW162435

Clutch vent pipe? The 993s have this. Just a guess

Andreas

Gary R.

Nothing goes there on my 78SC.. unless an idiot puts the crankcase vent hose on there by mistake after it blows off the oil tank neck (cause the clamp wasn't tightened).

Don't ask.

GT-three

i had the same symptoms with my SC,after taking it to numerous mechanics.the 1 and my now only mechanic found a loose vacuum hose.open the hood and let the car idle,listen for any king of suction noise.i would also do a Techron treatment.run a bottle on a 1/4 tank of gas and rev the #$%^ out of it.just my 2 cents

GT-three

oh..also may want to check the distributor.these cars are so dam hard to troubleshoot.

Peter Zimmermann

brewer: Well, it was worth a try, and with your symptom is often the solution. Don't worry about the hose connection on the right side of your airbox, it's not used on your car. It should have a rubber plug in it, but if not all that happens is a small amount of unfiltered air makes it into the engine compartment. Now, back to your problem, if you're still fighting it. (1) Did you wash your car and put it away cold? If yes you might have moisture inside the distributor cap. (2) With a good dentists mirror and a flashlight look at the forward side of the throttle body. There are a number of vacuum connections that are metal tubes that press into the aluminum housing. I've seen a few times where one of those tubes, with the vacuum hose connected to it, has come loose, which will really disturb your mixture. Let us know if you're making progress, hopefully your fuel guage sender didn't die and you're almost out of gas!
Pete

madbrewer

OK so my hat's off to the GURU! It was the pulse valve control relay afterall. I did the check that you suggested and I DID hear a buzz but as soon as we bridged the tabs where the relay plugs in it ran like a dream, pulled them and it instantly ran like crap again. So in the end it was a Bosch relay to the rescue. Thanks for the incredibly accurate advise!!!!

Peter Zimmermann

brewer: Outstanding! Keep the shiny side up!

Pete