Flashing check engine - no codes
 

Hi,

1998 5.9 178000 - yesterday I did a fill up 20+ gallons drove about 3 miles and hopped on the interstate and the check engine light started flashing and the engine started stumbling once I got up to 70 mph. Almost like bad or no fuel. I slowed down to 60 and the stumbling ( the whole truck was vibrating violently) stopped. After this the truck ran fine - smooth running all the way up to 80 mph.

The next day a code scan showed no codes. The fuel pump is original I'm thinking it may be on the way out. Any ideas?

The plenum has never been replaced I'm pretty certain it needs it, as a quart of oil occasionally disappears every 1-2k miles.

Also in the ~18 years I've owned the truck the check engine light has never come on.

Thanks, Jim

Flashing CEL indicates misfiring. That is where the violent shaking comes from. It may have just been a fluke, since after you slowed down, it quit doing it.

Fix the plenum, as that is a likely contributor to the problem, and also replace at least the front O2 sensor. Then it's just going to be a waiting game, to see if the problem recurs.

Flashing CEL is bad. Sever misfire as stated. Stop driving it if it does it again. You can do serious harm to your engine.

It hasn't done it since. 2 days ago the battery died(12 year old diehard). Not sure if this could cause the problem.

Plenum Is original but probably needs it.

Thanks for the responses.

Jim

Was there by any chance a tanker dropping a load of fuel or just pulling out when you got to the gas station? If so, the bad fuel idea may have some merit to it.

Didn't see a tanker but it took forever to complete filling the tank. Everyone was complaining how slow the pumps were. I'm wondering if the pumps slow down when there is not much left in the tank and/ or perhaps it Sucks up the dregs/water at the bottom of the tank.

Yep, you will get slow flow when the tanks are getting toward the bottom. Unfortunately, it also picks up all the crap that has accumulated in there.....