89 5.7 running rich

Gramps said:

Check the coolant temp sender(the one by the thermostat housing on the intake) when they fail the exam defaults to reading it like it’s -40 degrees and DUMPS fuel in.

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Schurkey said:

If the exhaust is stinky, eye-burning "rich", then first off, you've killed the catalyst. Second, the most-common cause of eye-watering exhaust is MISFIRE.

This truck is crying out for a scan tool to look at the data stream--and for someone to inspect the ignition system.

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001pewter said:

I read that also, but does it effect the gauge at all? My gauge seems to be working fine. Is there anyway to test it or just buy a new one.


Edit: found the resistance chart in another thread, will give it a check tomorrow.

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Gramps said:

No. The guage is referenced off of the temp switch in the side of the drivers cylinder head tucked between cyl 1-3. The ECM uses signal from the coolant temp sender by the stat housing on the intake, that’s the one that matters.

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xx94Z71xx said:

they are cheap to just replace. and they are known for going bad. did u check the resistance hot and cold? dont remember the exact values but last time i had them i found them on a google search.

a bad fuel pressure regulator can also cause a rich condition, along with any type of leaking or seepage on the fuel lines.

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evilunclegrimace said:

Yes a leaking FPR can cause a rich condition.
NO! Leaking/seeping fuel lines do not cause a rich condition. They are outside of the Throttle body and any leak/seepage is not pulled in to the intake to be burned.

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