random misfire '97 expy 290k

IMINYOURCHAIR · Oct 12, 2014

as the title says, I've got a misfire that is more frequent on #8 followed by #2. I pulled the number eight plug and was greeted with this from #8. these plugs all have about 14k miles on them. she does burn some oil but I keep it topped off. from what I have read this is some type of ash deposit that is normal with an oil burning engine. I wouldn't say I burn more then 2 qts over 4k miles of mixed highway/city. I also do get to go WOT a couple times a month to stretch her legs some.

I do plan to replace the coil pack I believe is at fault then check what plugs I can get to w/out pulling the fuel rail to check up on them.

FordandPolaris · Oct 14, 2014

You could just switch a coil pack from a known functioning cylinder to see if the misfire moves or stays put. Also, with that many miles, fuel injectors could be an issue as well.

IMINYOURCHAIR · Oct 14, 2014

what do you think of the spark plug I uploaded a picture of? anything unusual about how it looks?

FordandPolaris · Oct 14, 2014

http://www.gnttype.org/techarea/engine/plugs.html

I use this website a lot, it looks like excessive oil buildup to me.

IMINYOURCHAIR · Oct 14, 2014

Yeah, she does use some oil as I stated in the OP..I will pull the next plug I can access without removing things and then swap the two and see where we go.. I will also swap the plug wires from 8 and whatever wire is the same length and see if the code follows (should it present one) if it does not follow and keeps showing misfires on 8 I will just go rent a compression tester and go from there.

she does have 290k miles as of today so the engine may be done "lasting a long time" I just don't have the $$ to drop on a new or used 4.6... even so I wanted to also do the trans swap to a 5 speed but I feel it's a pipe dream for a worn out truck...

IMINYOURCHAIR · Oct 14, 2014

I should've went ahead and re did the tune up back when I had the $$ and went with proper motorcraft plugs/wires and changed the coils out. I didn't because the autolite parts I put in were doing so well and I pulled autolites out of it back at 276k miles here is a pic of that for comparison. (plugs aren't in order they fell off the seat when I put them there..) the oil deposits are still there

FordandPolaris · Oct 14, 2014

You can get a running expy for as low as 1500 bucks. Or a fairly decent one for around 3-3500. Cheaper than the motor swap itself

IMINYOURCHAIR · Oct 15, 2014

yeah, the thing about the cheap expys here is a lack of knowledge when maintaining them. spark plug blow out galore and oil starvation are two things that I see often on craigslist here. then there are the "good condition" ones that I would have to go back and do exactly what I've done with mine. stage zero as I call it.. oil, plugs/wires all filters etc

FordandPolaris · Oct 15, 2014

I would do a compression test on that cylinder. It clearly is burning quite a bit of oil, if it has no compression, the motor needs a rebuild anyways. You can rent the tester for free from most auto parts stores.

IMINYOURCHAIR · Oct 15, 2014

I will do the compression test and see but truth be told I don't feel it's the compression. I haven't had a misfire for about 2 days.. then I am climbing a hill in 4th (pre downshift) and it stutters a couple times holds then down shifts and continues as normal... I think it's going to be bad plugs for the motor combined with the oil problem

random misfire '97 expy 290k

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