Aww Mann... As much as I like getting help, I'd WAY PREFER to be giving it! (i.e. I ain't havin' a problem)

'99 Expy w/ 203k, rebuilt at 130k... Timing chains and tensioners were done 3 weeks and about 500 miles ago...
https://www.ford-trucks.com/forums/1...ing-noise.html
Purred like kitten until all the sudden...

Severe misfire under load, and rough idle... Cat smell...
Codes 0304 and 0306

I've read a bunch of misfire threads, and the consensus is coils, wiring to coils/and/or injectors... I had coils 1-4 off, and plug 1 out because the pass VC is such a PITA... (but not coil 6) Also some tugging and bungee cording the pass loom to get the VC off...

What gets me is 0306, on the nearly opposite corner of #4... Both happened simultaneously outta the blue... Makes me lean more toward severe vacuum leak, but I can't find one... Pulling #4 or 6 coil or injector connectors while at idle and 1500 seem to give the same speed reduction/stumble

Do we know if injector or coil grounds are shared by 4 & 6? I'm going to check crank and cam trigger leads/conns... Recheck all coil/inj conns, and swap coils 4&6 with 1&5....

I DID NOTICE... that with live data, my downstream O2 sensor voltage was EXTREMELY static... i.e. O2S11/12/21 were doing their thing... But O2S22 was basically moving from 0.865-0.870v if it moved at all... Bad O2 sensor?

Other thoughts= Fuel Pressure, ERG.... Any recommended procedures for checking?

ANY thoughts are extremely appreciated, and I will try to have some more data tonight!

Thanks!
HS

 

Well...

I have an update that maybe somebody can gain some insight from!

This truck has been sitting since the misfire, and the battery went DEAD-DEAD-DEAD... Like erased codes dead...

Before I discovered this, I went and swapped coils with the offending code cylinders, 4 to 1, and 6 to 5... So if we had a coil problem, I would expect the codes to jump to the new cylinders 301 and 305...

When I jumped and started the truck, it ran like gangbusters with NO MISFIRE .... UNTIL... It warmed up... As soon as it did, I had the same stumbling, or even worse misfire... NO codes pending or otherwise were thrown... And I didn't want to keep pushing things and melt the cat...

Soooo...

What makes a "reset ECM" able to run the engine without misfire until the engine warms???

Thanks for lookin'!

 

Im going thru the same **** . New motor at 120,000 miles and mechanic didn't put on new coils. Miss fire on 2 plugs. I bought a set of Accel coils from Amazon and all was great until last week. Now at 138,000 I am getting the same coded you are. I reset the codes and when it gets warm or Im pulling a trailer I get the over fueled. Tomorrow I going to Ford and get me 8 new Motorcraft coils. I got what I paid for from Accel.

 

Hiya LG...

Well that sucks... Seems however that there should be another problem causing the issue... If you have no problems until you push your truck...

I'm thinking there is a fuel loop problem... Like an 02 sensor, fuel regulation/pressure, another "heat related" sensor out of whack???

Does seem strange with your "new motor" at 120k, and my "fixed compression/timing chains" we now are getting misfires...

 

I thought I would follow this up with "THIS PROBLEM" solved...

Other mysteries continue:
https://www.ford-trucks.com/forums/1...l#post15253713

https://www.ford-trucks.com/forums/1...l#post15253718

Major problem was the vacuum elbow on the back of the intake mani... after fixing this, I was able to drive the truck enough to see that after a coil swap my misfire code moved holes...

8 coils and plugs later, she ran like a banshee... until the stupid PATS problem...

Thanks for your help guys!