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Running rich and running rough

posted by  Don Foster on  Sun Dec 29 10:39 CST 2002
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last visit: Sun Oct 5 11:53 CST 2014
[RELATED]

Three things are known to cause a rich condition:

1) Bad temp sensor -- the two-wire sensor under intake #3 (the sensor under intake header #2 is for the temp gauge).

2) Bad AMM, but you disconnected it and the problem remained.

3) Bad fuel pressure regulator.

I'd bet my cold beer on a bad fuel pressure regulator. They fail frequently. Pull the small vac line off the nipple at the intake and inspect or sniff for raw gas in the hose. This indicates a punctured diaphragm, and the raw gas will bypass into the intake manifold via the vacuum hose.

If the temp sensor opens (infinite resistance) OR if the connections to it fail (seen it happen, 'twas a real head-scratcher) then the FI ecu interprets this as a very cold engine (like minus a zillion degrees) and POURS in the fuel to compensate.

Those FI control units almost never fail.
--
Don Foster (near Cape Cod, MA)






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