'86 930 Suddently sputters and no power > 3,000 RPM

[flightlead404]

I have just acquired an '86 930.

Its in pretty great shape, but does have an oil leak and smokes like a Clemson frat house from underneath.

It was running great and pulling like a freight train until this afternoon.

I drove over to my workshop, getting the engine hot in the process. Then used a sprayer on my air compressor to spray off oil and grime from inside the engine compartment and loads from under the car. Engine was not running during this process.

Also added a quart of oil.

That's it. Didn't disconnect anything, didn't change any filters or plugs, nothing.

Now when I'm driving it seems low on power through about 3,200 but suddenly at 3,200 its sputtering and bucking and has zero power.

I can't see any connections or vacuum hoses loose.

[turbo owner]

Originally Posted by flightlead404

I have just acquired an '86 930.

Its in pretty great shape, but does have an oil leak and smokes like a Clemson frat house from underneath.

It was running great and pulling like a freight train until this afternoon.

I drove over to my workshop, getting the engine hot in the process. Then used a sprayer on my air compressor to spray off oil and grime from inside the engine compartment and loads from under the car. Engine was not running during this process.

Also added a quart of oil.

That's it. Didn't disconnect anything, didn't change any filters or plugs, nothing.

Now when I'm driving it seems low on power through about 3,200 but suddenly at 3,200 its sputtering and bucking and has zero power.

I can't see any connections or vacuum hoses loose.

My new to me 79 turbo has the exact same problem, 4 broken head studs is what I believe my problem to be.

[flightlead404]

Yeah, I've had that problem in a prior 911 SC. I don't think its the issue here. For one thing, you can hear broken head studs in my experience, as the hot gasses are forced out between the head and barrel.

This doesn't sound like that.

Further, it hasn't been driven hard recently, just warmed up. It drove fine, the it didn't.

[Roby466]

o'rings going to the intercooler? When boost tries to go on but leaks out of those you would end up way rich...

[flightlead404]

Checked all the electrical connections, vacuum lines, spark plug connectors, distro cap, hoses and O rings etc. Don't see anything amiss.

Problem came on suddenly.

So, I let the car sit for a couple of hours and cooled down. Took it out for a drive. It was great, no problem, for the first 3 minutes, then suddenly the problem is back.

No power, and severe lugging, above anywhere from 2,800 to 3,400 RPM.

I'm clueless.......

[kenikh]

Boost cut

[oilonly]

Are you sure you didn't knock the black relay in the electric panel loose when spraying around? That relay powers your O2 sensor, if disconnected you will run lean. Picture of the engine compartment might help.

[mark houghton]

Originally Posted by Roby466

o'rings going to the intercooler? When boost tries to go on but leaks out of those you would end up way rich...

Look here first. Head studs are one possibilty but the worse possible scenario. Usually, it just poor connections from the turbo to the intercooler. You crank her up on the boost scale and a failing o'ring gives way. Very common. Next thing you know, we'll be directing you to a total rebuild. You'll have to auction off your first born child.

[flightlead404]

Originally Posted by oilonly

Are you sure you didn't knock the black relay in the electric panel loose when spraying around? That relay powers your O2 sensor, if disconnected you will run lean. Picture of the engine compartment might help.

I didn't take the plastic cover off the rear fuse/relay panel. In fact, I didn't spray much there at all. Mostly underneath and around the oil tank etc.

Something loose, or wet, was my first inclination. I checked as much as I could see. Removed and re-installed a few connections. Checked all the plugs on right.

I have let it cool down and then driven it twice. Both times its great when cold, solid idle at 1,000 rpm and pulls like a freight train. When it warms up the idle is hunting around 400-900 rpm and the power is gone.

Its NOT the Dash In Your Face overboost cut off. Its like I ran into a pool of molasses and there engine is slogging and I head "dadadadadadadadadada" rapid fire.

Sounds and feels to me like its suddenly missing badly, or a fuel shut off, or suddenly running lean. I'll check the relays tomorrow.

Boost is being indicated.

Dammmit I was planning on picking up my girlfriend on her last day of school in it tomorrow. Now I'll have to take the beater :-(

[JFairman]

Sounds like water sprayed on the motor is partially shorting something electrical now. The distributor may have water in it and the WUR is not waterproof around the plastic electrical plug.
Maybe it will run better when everything dries out.

[mark houghton]

All those relays control the fuel pumps in one way or another....either there's fuel, or there's not. They don't cause lean or rich conditions. Yeah, the O2 sensor circuit could be malfunctioning, but I don't think it would cause the extreme conditions you're reporting. It was running crappy BEFORE you hosed her down, so I'm thinking don't focus on wet stuff. Sputtering and bucking (your description) past 3200 rpms still sounds to me like an air leak....you're just beginning to build boost, and that boosted air is leaking out, creating an overly rich condition.
Suggest you take the girlfriend out anyway....impress her with the ambiance and historic stature of one of the world's most famous Porsches...but just keep your foot out of her (I mean the car) until you get it sorted out.

[smurfbus]

Huge air leak like IC to TB popping out or the elbow from the metering plate? Is it possible its very rich when this happens? If wur is not getting power it goes cold fueling unless heatsoked.

[pdx930]

Another thing that transitions at 3000 rpm is the operation of the frequency valve. It goes from O2 sensor feedback control to fixed duty cycle at 3k rpm. If you have a big air leak, the lambda system can compensate for some of it below 3k but the it will quit trying. Disconnect the O2 sensor and see if it will still idle.

[smurfbus]

One other thing could be broken spark plug but they tend to misfire at all rpms when bad.

[T77911S]

i am with jim. let it dry out. you got water down in something electrical be it the dist or even just a wire/connector.
in the mean time i would pull the IC and just make sure all the O rings are good. i found it best to keep extras on hand.

as mentioned, 3k is where it transitions from closed loop to open loop

[puddy]

My car did this when my battery cable was loose. Bad ground somewhere?

[9dreizig]

my does the same,, check your spark plug wires

[wjfk32]

Switch your Red-Fuel pump relay--see what happens.

[wholio94112]

...turned out being the intake elbow from plunger to turbo downpipe on the left side of engine bay...under boost, it would just collapse...stoclk replacements at the time, a few years ago were about 60 bucks, but I went with the silicone fabspeed model and haven't dealt with problems related to that unit since...good luck...

[wholio94112]

...disregard previous post...probably not relevant...scary to think I type faster than I think...