this was yesterday afternoon...after driving all day w/o issues:
driving along fine and then a/f started nuttin' up...12...16...13...17...etc...very fast swings from rich to lean...

checked logging fp...
16...52...19...48...32...50...18...42...etc...swin ging so fast you couldn't think or say the psi before it would go the other way...

eventually would peg a/f gauge lean and stay there...then cut-off...

pull over for a few minutes...restart...drive a few minutes...
same thing all over again...

no indications that it is IAT or ECT related...

seems that fpr would be bad or not...not self healing or heat affected...

seems that pump being bad would do it more often as well...

fuel pump relay?
power...no power...power...no power...etc...???
underhood temp related?

 

What's your fuel setup? Inline? just intank? Sounds like a bad wire, damaged, burnt, loose connection or whatever.

 

intank w/ Walbro replacement...done over a year ago...
it did this once before, after the new motor install...w/ original, stock wiring...
have upgraded since then with better, bigger wiring...now doing it again...

 

quadruple check your wiring connections.

If ya have a multimeter, especially one that logs, read the voltage going to the pump (coming off relay). Drive and watch. This will at least tell you if it is at the relay. I put the multimeter on my windshield, duct taped. Leads went to the relay. Everything was fine. Then I ran leads from the terminals on my inline pump (tank harness for you) and found I had wacky voltage. Then found where the headers got a hold of the wires back in the day and corrosion finally took it's toll on the wire.

If you have constant voltage to the pump harness then you know your prob is in that tank.

 

what symptoms did you have and when were the symptoms present?

did fine this morning...cooler underhood temps...
its hot today...maybe I can get it to nut up again...then swap relays and see if it continues...

 

The same symptoms. FP was all over the place. But mine was the inline, so it was becoming a restriction when it wasn't powered, the stocker was trying to push thru I guess. It didn't mess up too much at idle, only driving around.

 

no problem on the way home from work this afternoon...
then drove into town w/o issues...
on the way back, however, it nutted up 4 times before reaching the house...
each time it happened was right after I had slowed down to stop or turn...
again...no indications of anything being logged/scanned triggering this...

about 20 minutes later, I swapped out the fp relay for the horn relay...
took it for a drive for several miles w/o issues...
went WOT a few times...
did not hit any red lights on the way out of town...
turned around and headed back...
right before I got home, when I was slowing down to turn onto my road, it nutted up but recovered...
nutted up again as I was slowing down to turn into driveway...then pegged lean and cut off...

??? maybe I'm in denial, but I can't see this as electrical connection issues...

 

no issues on the way to work this morning...cooler underhood temps again...
gonna replace the 220k mile fpr today...even though I don't think that's the problem...

 

Fuel filter or probably tuners fault When my pump was going out I would get a lean pop/backfire type of thing when i gased it. Maybe FPR will fix it.
J/K Jerry

 

changed fuel filter when new motor was installed...then again a few hundred miles later when I noticed it was leaning out @ WOT...

I HAVE HAD THE POP/BACKFIRE AS WELL...forgot to mention that...