Bad Fuel? Redline SI-1 Overkill? Exhaust Leak?
 

I am finishing up my second bottle of Redline SI-1. (I Added a full bottle on each of two consecutive fill-ups.)

I added the second on Thursday just before a road trip from Delaware to Virginia. On Friday, I noticed the car feels bogged down -- heavy steering and not as swift acceleration. There is a low, steady, sputtering sound from the muffler (seems to be emanating from the forward-most part) that sounds like a small, baritone motorboat – most noticeable at idle and disappears at highway speed. Engine also seems to roar and fuel gauge is intermittently erratic just below the Full mark.

Prior to Thursday:
Exhaust was silent and the car behaved well. Fuel economy was normal and the gauge rock steady. Visual inspection of the muffler reveals no holes, and the sputter appears to be coming from where the pipe joins the muffler (I see some welding/brazing occurred there).

After Thursday:
* Added second Full bottle of Redline SI-1 on Thursday (Aug 13th) -- added first last weekend (Aug 8th).

* Also on Thursday car was jacked up high at the left front for about 4 hours while vainly attempting to adjust a defective NSS switch.

* On the road trip to VA I passed through one road construction zone and kicked up some pebbles at low speed. If one punctured the muffler I should be able to see the hole.

* I have experienced this bogged-down behavior once before on a trip from DE, and it was also an occasion when the car was jacked up on one corner for a long time while I replaced the NSS switch.

I passed emissions & safety inspections today with no issues. When tech lowered car from jack I noticed muffler & tailpipes bouncing, as if a hanger was missing.

Is it possible the Redline liberated some fuel system mud that is causing this behavior? (The erratic fuel gauge tells me it is cleaning something.) Or did I crack the exhaust?

Possible, but not likely. I did have this happen with a heavy cleaning dose (ten bottles in 150gallons of diesel) of fuel system cleaner in an older diesel coach so I do say it's possible if there was enough crap in the tank.

Sounds like you're on your way to checking fuel volume/flow and perhaps a new filter, but you already know the exhaust is bad so a good place to start.

I'm going to burn through this tank and see what happens. At every oil change the previous owner's shop added "fuel additive" and "solvent." Based on the costs I assume the additive was BG44K, with a solvent (Berryman?) added to liquefy whatever the additive liberated.

As of this evening, acceleration feels stronger and steering is lighter so I have more power. The exhaust sputtering is a little bit quieter -- or perhaps higher pitched. I visually inspected the rear and center mufflers again and they appear to be sealed tight. There is significant vibration from them, which is strongest towards the center one. I'd need to have the car on a lift to see (and feel) around the very tops of them though. Because this same vibration/sound has occurred before (approx. 1 year ago), and went away, I am not 100% certain the exhaust is bad.

Regardless, a new fuel filter will likely be required after I burn through my present fuel.

Or the cat is plugged.

Also, depending on what "solvents" were used in the fuel, the fuel lines might be swelling/collapsing internally.

Thought briefly about the cat but that would have impacted emissions, and my HC & NO numbers on Saturday were actually down from 2 years ago at my last inspection.

Was out in the wee hours of the morning, when the car was cold, to do the laser test. The only visible beam was at the tailpipe. Also, on the last drive, the sluggishness was largely gone. Hopefully the sound will go with it.

UPDATE:
This time used a wet rag to more completely block tailpipe. Sputtering and vibration stopped completely. :eek:

Sound is no longer baritone, but has become a deep bass, now less noticeable (and zero vibration felt) at idle whereas before it was more noticeable at idle.

Also added solvent to fuel -- Berryman B-12.