Running too rich / misfire

Doug Yoder audifan at
Thu Sep 15 17:47:45 EDT 2005

Hi everyone-

Some of you may remember me from the q-list - now I'm going to buy a 200q20v,
but the current owner and I are working on getting it running first.

It was running very rough, sounded almost like it wasn't firing on all
cylinders.  All the spark plugs were black, and black smoke would pour out of
the exhaust.

We put a new cap and rotor and spark plugs on it, no help.  The new plugs got
sooty almost instantly.

We found the fuel pressure regulator was bad (leaking fuel out of the vacuum
line), so we replaced it, no help.  We temporarily swapped in a known good ECU,
no help.  We have tested every sensor that feeds the ECU except the MAF, and
everything specs out.

The crankcase breather hose was rotten, so we replaced it with some new hoses,
also one other vacuum line we replaced, no help (well, it runs somewhat
smoother, but still has the rich condition and misfire).

The only code is the hall sender, but the engine starts - I was under the
impression that if it were actually bad, the engine wouldn't start at all.

We checked the timing marks on the flywheel, cam sprocket, and distributor -
everything lines up perfectly.  We checked that the plug wires are on the cap
correctly.  We checked the resistance of the coil - OK.

We pulled the injectors and did a spray/firing test - all OK, none leaking.

The next step seems to be double-checking the MAF, and looking for more vacuum
leaks and/or intake obstructions.  The Michelin man hose is OK, looks like it
might have been replaced recently.

Anyone have any bright ideas to share?
Thanks in advance,
-Doug Yoder

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