Suddenly a Sooty Exhaust from my 4.9

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Jan 21, 2020 | 01:32 PM

DPDISXR4Ti

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From: New York

Suddenly a Sooty Exhaust from my 4.9

I've recently noticed that my exhaust has gotten smellier and on start-up it will leave a sooty spot on the driveway (downward facing exhaust tip). It's also running a bit rougher - nothing terribly noticeable, but not as smooth as it was.

I haven't done any diagnostics yet - no error codes so far. Any best guesses? I'll start with a compression test and go from there.

Jan 21, 2020 | 02:10 PM

rla2005

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From: Kentucky

Start with the easy items first. KOEO/Stored Code check. If good proceed to KOER tests. If good check the fuel pressure and inspect the fuel pressure regulator for signs of a ruptured internal diaphragm. Pull a spark or two then inspect for signs of rich A/F ratio. If they are fouled, inspect the rest of them.

Jan 21, 2020 | 02:10 PM

groundrat

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From: New Hampshire

Could be a sticky injector or an O2 sensor reading extremely lean. Did you pull codes and get the all clear 111? Or just no check engine light yet?

Jan 24, 2020 | 09:23 PM

DPDISXR4Ti

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From: New York

Haven't had a chance to dig any further into this, but thanks for the thoughts. Indeed I need to actually pull codes; so far, just going by no MIL.

I believe this is more of an oil soot rather than rich fueling soot, but it's worth checking all possibilities.

Jan 25, 2020 | 12:50 PM

groundrat

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From: New Hampshire

These truck do not trigger the check engine light when most of the codes are set. You could have half a dozen codes and never see that light. It only takes a few minutes to jump the EEC connector and count the flashes.Or pick up an Innova 3145.

Jan 25, 2020 | 01:50 PM

DPDISXR4Ti

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From: New York

Quote:

Originally Posted by groundrat

Yep, understood. I already have a Rotunda Super Star II, so no need to buy anything, just need to get out there..

Feb 15, 2020 | 03:12 PM

DPDISXR4Ti

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From: New York

Finally got around to pulling codes yesterday and got a 21 (ECT) and a 24 (IAT). I suspect they both use a common ground - I wonder if that could be the actual issue since it would be odd for both those sensors to fail at the same time.