GPS430E

2000 W210 E430: Had multiple cyl missfire and random missfire codes. Monitored o2 sensors, replaced pass side pipe with cats, sensors now reading normal, flip flopping voltages. Third test drive hot, chk eng light and started missing, hard miss. Code for #5 cyl missfire. keyed off and right back on, engine miss gone, consistently will clear dead miss. WOULD APPRECIATE SOME GOOD ADVICE ON THIS. New plugs appx 6 mos ago but converter may have been bad then as one side plugs were sooty looking according to son in law. Garage has also replaced crank sensor because of hard to start problem. HELP PLEASE .

Racin_fool

take the coil and plug wires from cylinder 5 and swap them with the ones from cylinder 1.. See if the misfire moves.. If it moves, I'd replace them.. If it doesn't move then you may have a sticking injector or something else going on.. Atleast you rule those items out if you move them and nothing happens so you don't have to throw more money at it..

GPS430E

Sounds good to me! Thank you VERY MUCH for taking the time to reply. I will try that and reply.

GPS430E

OK, REPLACED PLUGS #5, SWAPPED COIL AND ONE WIRE WITH #1, TEST DROVE OK UNTIL "ROMPED" ON" . IMMEDIATELY SET CODES P305, P307 AND P300[random miss]. RAN ROUGH AND WEAK. O2 SENSORS BOTTOMED OUT LEAN[zero]. APPEARS COMPUTER TURNED OFF INJECTORS TO 5 AND 7. RESET AND RAN FINE AFTER KEYOFF. NO CODES OR MISS ON BANK WITH NEW CATS. MAKES YOU WONDER DONT IT? WHATCHA THINK?

GPS430E

TO CLARIFY, MISS IS ON DRIVER SIDE WITH OLD CATS, SIDE WITH NEW CATS CLEARED UP, NO CODES OR MISS. JUMP IN AND TELL ME WHAT YOU THINK.

E-420

reason it runs fine on startup and for a while even with misfire is that after enough misfires, fuel is completely cut off to the cylinder until it engine turns off. So an occasional misfire won't be noticed much, but if enough occur, then with fuell off, it "misfires" every other engine revolution and you notice it. It's to protect the cat and meet emissions.

GPS430E

YES. I HAD ASSUMED THAT WAS THE CASE, QUESTION IS WHY? I AM GOING TO TRY MONITORING DATA STREAM OR GET SNAPSHOT UNDER CONTROLLED ACCELERATION JUST BEFORE CODES SET. I AM SUSPECTING CATS ON DRIVER SIDE MAY BE RESTRICTD ALSO. THANKS FOR FEEDBACK E-420.

GPS430E

JUST AN UPDATE....... DAUGHTER HAS BEEN DRIVING CAR WITH NO PROBLEMS. DOES OK IF NOT RACING AROUND I GUESS. SUITS ME FINE!! LAST TIME I TRIED TO MONITOR AND SET CODES, IT RAN OK ALSO.