hmm what else

rywegh

Original poster
Member
Jul 4, 2012
56
short story changed fuel filter and truck went crazy. throwing misfires and engine loped. replaced plugs with delco's, cleaned throttle body and replaced fuel filter once again. got P0302 it switched to P0304 when I swapped coils. so I got a new coil and replaced number 4. truck runs better but I can still feel something. It is also throwing P0300 intermittent misfire?? but the lope is not there and is the best it has run since the first FF change.

What else can I look toward? run another fuel cleaner through it? Techron? or is there something stronger? really getting tired of this acting screwy. The pessimist in me says I screwed up somehow when I changed the FF.
 

SAR85

Member
Jan 31, 2012
74
Have you checked fuel pressures? Maybe the filter is bad and causing low fuel pressures causing random misfire (P0300).
 

navigator

Member
Dec 3, 2011
504
have you cleaned your throttle body and disconnected the battery for 30 mins so the PCM can do a relearn?
It might not matter but anytime you toy with something related to air/fuel I would disconnect the battery.
 

rywegh

Original poster
Member
Jul 4, 2012
56
I did not disconnect batt and do throttle body again when I replaced the coil. I guess that would be my cheapest thing to do. I did erase codes with a code scanner if that makes a difference.

As for ff this is the third ff within a month. orig - the duralast I replaced it with and thus all my issues started - now on a new ff from purolator. in between the two new filters I did clean throttle body. as I put the puro ff in I also replaced the plugs with delco's and cleaned throttle body again. I was then getting a misfire code specific to a cylinder, swapped coils and misfire moved with it. replaced said coil, now just a random misfire. What am I looking for with the fuel pressure? ie what could be an issue there? I'll have to get a fuel pressure gauge to check it.
 

Regulator

Member
Nov 20, 2011
2,496
navigator said:
have you cleaned your throttle body and disconnected the battery for 30 mins so the PCM can do a relearn?
It might not matter but anytime you toy with something related to air/fuel I would disconnect the battery.

It sounds like the PCM needs to reset so it can relearn. I would say that the battery disconnect is the best route to go before throwing more money at it.
 

SAR85

Member
Jan 31, 2012
74
Regulator said:
It sounds like the PCM needs to reset so it can relearn. I would say that the battery disconnect is the best route to go before throwing more money at it.

I agree. ^^^

Also, given that you've tried 2 different fuel filters I think a defective one is unlikely to be your issue. So you can probably skip fuel pressure testing, at least for now.

The other thing to check would be to make sure the coils are seated properly on the spark plugs. It is easy to not seat them properly. You could also try using dielectric grease in the coil boots if you think you are having spark/contact issues.
 

rywegh

Original poster
Member
Jul 4, 2012
56
The light finally came on solid. Scanned it and it is giving me P0304... will try to reseat it. wonder with it being a new coil if the boot might be a little stiff and I didn't seat it all the way... but will do the throttle body cleaning and pcm while apart.
 

strat81

Member
Dec 29, 2011
399
Not sure if it would effect things, but is your filter on correctly? The ones I've used are marked IN and OUT.

IIRC, pressure at the rail with the key ON should be around 55psi.
 

rywegh

Original poster
Member
Jul 4, 2012
56
These were all nice suggestions guys... but alas it was my dumbass! When I replaced the coil, wait for it, wait for it... I miscounted and replaced the wrong one. as soon as I pulled the breather box off I saw itall nice and shiny in the number 3 spot and not number 4.

Thank God I hadn't thrown the old part out the other day.

Swapped out and buttoned it back up and purrs nicely.

give me a day or two and I will do the belt, thermostat and coolant temperature sensor, Stay tuned for my next idiotic question.
 

McGMT

Member
Jun 17, 2012
621
rywegh said:
These were all nice suggestions guys... but alas it was my dumbass! When I replaced the coil, wait for it, wait for it... I miscounted and replaced the wrong one. as soon as I pulled the breather box off I saw itall nice and shiny in the number 3 spot and not number 4.

Thank God I hadn't thrown the old part out the other day.

Swapped out and buttoned it back up and purrs nicely.

give me a day or two and I will do the belt, thermostat and coolant temperature sensor, Stay tuned for my next idiotic question.


Always remember, there are no stupid questions... There are only stupid people... Glad you fixed your issue and good luck with the next job...
 

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