Hilton

This sounds baffling.

Idles ok and runs up to 2500rpm says that its likely not the MAF, or ECU's.. so back to basics.

1. How old is the fuel filter?
2. Have you checked the part number on the fuel pump? (cheapo ebay replacements, or ones from other cars, may not provide enough fuel)
3. What spark plugs are installed? Whats their gap?

Both answers can be found by removing the cover off the fuel pump (its external) - just takes a minute with a 10mm wrench. You don't need to lift the car off the ground etc.

ryalex

In neutral it revs easily up to about 4700 and cuts out.

ryalex

1. Fuel filter should have been replaced yesterday since I bought a new Mahle one with the tune up kit that I got from 928 Motorsports.

2. I'll check the fuel pump part number in a minute.

3. The plugs are brand new NGK ones, installed yesterday.

ryalex

I switched the horn relay and the fuel pump relay, that wasn't it.

ryalex

reading JDS Porsche page again the symptoms still seem like MAF failure and the "limp home" mode. what are the odds of two bad sensors in a row?

Avar928

If there's any local 928ers in the area, you could try swapping it with their MAF. I believe it's best to have the MAF rebuilt as they are prone to failure with age. I sent mine to Kevin at Injection Labs. When I first started working on mine, I had done a tune up including new ignition wires but she still felt sluggish. Rebuilt MAF and I got better performance.

However, she wasn't down on power as much as you're experiencing now.

Just as an aside, did they check compression?

Hilton

Limp home mode was what I originally thought - but your comments about it running ok and revving to 4700 in neutral made me think otherwise. Its worth investigating too tho.

A "bad" MAF is an old maf.. not necessarily failed, although some do fail. More likely is a dodgy MAF connector on the engine harness side. Check the MAF connector boot very carefully for cracks and frayed wires inside.

tv

Well, what you need to do is get someone with a normal running 85 to come by and swap their good MAF, EZK, and LH all at once into yours and run it. If yours runs fine then you can then swap back 1 of those at a time to isolate the bad one. But if it still has the same problem with all 3 then it is somewhere else. Fuel pump, final stages, harness, coil(s), wot switch,maybe even the pulse thing over the flywheel.

You said you switched 1 brain there are 2. These symptoms are similar to 1 being bad or also a massive vac leak. Do the lights flicker when the engine stumbles?

See section 03 in the WSM

Landseer

I've seen two working 928 MAF's be disabled during preventive spritzing with MAF cleaner.
Maybe they already had some other weakness, but its made me a bit gun shy.

Really awesome looking car, btw.

AirtekHVAC

I am very late to this thread, and have no input on your issues, but welcome, and enjoy...it will get sorted, and you will love it!

After all the running issues are corrected, consider a short shift kit...

VegasGnome

Ryalex,
You are welcome to try the MAF/computers that are in my '85 to see if it will help solve the problem. I am currently on a month long road trip with the car and will be back in Vegas at the end of the month.

sweanders

IMHO this is the best factory style ever of the 928.

fraggle

Check your spark plug wiring and coils! It really sounds like something is swapped or failing. There might be corrosion in the coil boots, too.

ryalex

I ended up taking it over to Carl's Place/900 Motorsports yesterday for their expert to fix it. I have faith in them.

ryalex

The good news is that everything was mostly correct with the car... looks like we might have narrowed the power loss down to something relatively simple. Going to try some things tomorrow.