Ed Petry

Hi everyone,
I have followed the discussions of the fuel issues our cars suffer and hoped none would become "my" problem.

SURE, ED!!!!

81 OB 4.5 5-speed. Looks unmolested other than a set of headers.

I haven't seen a thread that matches my issue but that may be my lack of understanding. Sorry, if that is the issue.

I bought my 928 in 2015 and have not really had a chance to drive it, work on it or just enjoy it. Between moving, having our first grandchildren and working, time was short. No time to make the 928 secure enough to drive. (Not secure for only me but to ensure the 928 is safe and I will not kill it by negligence.)
.
That changes this summer. Time to work on the car and enjoy the work and the results.

Over the weekend I replaced the two fuel lines from the chassis to the engine. No leaks and now I know when the rubber was replaced (Thanks to 928 INTL). Started and drove up the freeway like a 928 should. Felt wonderful!!! Cool.

Now the other side of the coin....On my first drive after an overnight cool down, I experienced poor performance after a bot or driving. Here's what happened.
started with 5 seconds of cranking over two attempts.
drove for 5 minutes
stopped for 20 minutes (had to thank a friend for helping out over the years)
drove for 3 minutes
stopped for 10 minutes (gave the 928 a proper sponge bath)
drove for 5 minutes. miss started during this time. within 1 minute after starting up.
Continued until end of trip.

Nothing hard or pushing the limits - surface street speeds. Simplify getting the car out to see what it feels like. Feels great otherwise.

What should someone start looking at?

Majestic Moose

Do you have any records for repairs and maintenance prior to your ownership? A stumbling symptom could be just about anything if everything is still mostly original but by your timeline this started after washing the car and that may be a clue. Did you wash anything under the hood? How old is the fuel?

Ed Petry

[QUOTE=Majestic Moose;15807064 but by your timeline this started after washing the car and that may be a clue. Did you wash anything under the hood? How old is the fuel?[/QUOTE]

Thanks for the reply. Appreciate it.

The records I have are spotty. The vehicle appears cared for but that doesn’t mean a whole lot in this case.

I did did not wash under the hood at all, exterior only.

Fuel is from December, when I topped it off and added a can of Seafoam.

andy-gts

I would check plug and coil wires first looking for signs of corrosion.

dr bob

With spotty records at best, I would:

-- perform the annual electrical maintenance procedures detailed in Wally Plumley's guidance. It's available now on the Pirtle tips site.

-- do all the catch-up maintenance on the ignition system. Start with new plugs (cheap) and inspect wires, cap and rotor. Replace those as inspection dictates.

-- Look carefully at the Green Wire that runs from the distributor to the spark box. As that wire ages and deteriorates, the performance of the ignition system gets less accurate and reliable. Inspect the connectors as well as the wire itself.

-- Do the full fluids service including what you haven't yet done of the following: Engine oil, engine coolant, brake fluid. Those won't solve a poor-running issue now but will lessen the distractions they will otherwise provide later.

-- Put fresh fuel in it. After driving out or otherwise removing the old fuel. New fuel goes in with a real fuel stabilizer like Sta-Bil any time there's a chance that the fuel going in won't be used up completely in a month or maybe two. Preservative/stabilizer is different from treatments like Seafoam. Use a treatment when it needs it, which may be now after old fuel sat in it. Use a stabilizer to prevent that need moving forward.

-- Replace a tired oxygen sensor. In a previous car's look, I could justify the cost of a new sensor every 25k or so just with the fuel savings. I don't put enough miles on the 928 to make that a good investment, so it gets one every 50k or so. It "just" got it's second replacement a few years ago.

-- replace all the oil and other vacuum hoses from the cam covers and under the intake. Originals are tired and cracked due to age if nothing else. Take lots of pictures and make routing diagrams for each hose so the new actually goes in and connects where the old one did. Even small vacuum leaks in those hoses will fool with the mixture. When the engine is cool, the mixture is artificially richened to support fuel condensation issues on cold intake tract walls. That will mask minor air leaks for a while while it hasn't warmed up.

Wisconsin Joe

SeaFoam is a stabilizer. At least it's marketed as one.

Ed Petry

Hi,
After some investigation it turned out to be a cracked vacuum hose connected to the air injection diverter valve on the passenger side of the engine. (PET illustration 108-00 item #22). It broke off in my hand. Time for a top engine refresh.
Thanks for the advice.