Bought a 1991 Brougham D'Elegance from an old geyser who did nothing but drive and change the oil. At 119,950 miles, the spark plugs were ORIGINAL, as were the AC Delco Cap/Rotor and numbered Packard Bell spark plug wires... Have a look at one of the spark plugs. Burned down from .035 to .055.
The car had a little bit of a rough idle, so I naturally figured that a tune up would fix it, no go...
So I drove 100 miles into the country with some Lucas Injector cleaner and 93 Octane in it, giving it a WOT whenever possible, no change, not even any black or brown coming out of the tailpipe.
Then someone in the Brougham/RWD thread suggested it may be an EGR valve, so I replaced that, no change.
Obviously, I am worried that I may be looking at a burnt valve. I didn't figure in that kind of work when I bought it, so I am looking for wisdom...
Could it be anything else? Basically, it is a very slight, but consistent miss. There is a small exhaust leak toward the front, probably on top of the catalytic converter, or where it connects. The miss is only noticeable when just rolling to a stop. You can feel a pulsating flutter. But on the road, she screams! One of the strongest TBI 5.0's I have driven (I've had 3).
If it is a burn valve, dare I drizzle some water down the throttlebody in an effort to break it up?