MFI odd revving problem (storage revival)

[jkarolyi]

I'm reviving a 1973 911E which supposedly had an engine rebuild just before it was stored 10 years ago and not run since. I've replaced every fuel line, filter, and fuel pump and had the tank boiled. I had the injectors rebuilt by Pacific Fuel Injection. I took the MFI injection pump and soaked it in Berryman's and made sure it worked properly.

Engine starts and idles perfectly (yay!), and revs somewhat OK when first started cold. There is a low, loud growl from the left side injection stacks when you rev the engine, while the right side is perfectly quiet. When warm it is much more reluctant to rev, it stumbles and will occasionally let out a loud pop (not a bang like a backfire) and a big puff of blue smoke out of the exhaust. The roar is still there at the left stacks.

While warm, I pulled the plugs and checked compression... 145-150 on all cylinders. Here's the wierd part...the left bank (with the stack roar) of spark plugs were all seriously carbon fouled (I had put in new plugs), and the right bank were seriously oil fouled. I cleaned them up and reinstalled, same problem.

Any ideas what the problem might be? How should I start diagnosing/repairing this? Do the MFI Check Measure Adjust sequence? I just thought the spark plug situation might give you a clue where to start.

[304065]

Is it roaring with the aircleaner on, or are you revving it with the housing off? It almost sounds like something mechanical is grinding- could it be the MFI belt drive on the port-side of the engine?

The carbon fouling and reluctance to rev and the popping and smoking suggest to me that it's too rich on the left side. BLUE smoke = oil, could it be that the rings never seated following the earlier rebuild? That would be consistent with the oil fouling on the starboard bank.

Work your way through check measure adjust and report on each step-- the rules for the linkage rods, etc., must be exactly adhered to.

Search under my name for "LM-1" for an interesting thread on how I set up a wideband 02 sensor for testing the MFI engine.

[jkarolyi]

I do have the air cleaner housing off. It's not a mechanical grinding noise, it's a normal Porsche intake growl but louder Maybe it's normal and the right side is faulty. I have a Unisyn to measure intake for each cylinder.

>BLUE smoke = oil, could it be that the rings never seated following the earlier rebuild?

That's what I was thinking, but it's only on one side of the engine (the side without the roar), and the compression is so good on all cylinders. Could the rings not be seated yet give good compression numbers?

[svandamme]

lm1 is pretty handy , my rebuild was running like crap, and had no idea what the mixture was like while driving, it just hesitated and ran rough, was hard to tell ... lm1 immidiately showed that it was running richer than uncle scrooge... it's a great tool if you have mfi, good bang for the buck