Would an o2 sensor really cause a misfire?

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Blain

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Ive been at this darn ram trying to get it to run right almost a year now.

I have a great idle and great acceleration. I however have a miss from 1300-1800 rpm.

Short history, father in law said it was running bad, did tune up (cap rotor plugs coil wires) and did not help. We tossed some new injectors on it and that didnt help either. By this point he was fed up and it started gushing oil. Ended up getting a new truck.

So far it has sat here for over a year and rotted fuel and brake lines. I replaced all the brake lines and fuel lines, replaced gaskets, and did other needed maintenance.

Recently I replaced the crank sensor under suspicion it was causing an erratic misfire. Turns out it was worn down to the metal pickup, but did not cure the miss.

I routed all spark plug cables in a manner they werent touching, have not dished out for taylor cables yet, but that is still an option if these wires dont ohm out right.

IAC is new. As well as the PCV.

Tested the throttle position sensor, I have 0.9v thru 3.6 with no spikes or drops (even when tapping)

Fuel pressure is a solid 39-50 at idle and rev (havent tested under load, hose isnt long enough to see with hood closed)

I have good compression on all cylinders (140ish)

What am I missing? Ive read many articles mentioning the oxygen sensor- could it really cause this missing even at a cold start?

The truck accelerates great and shifts properly, but at a 40-50mph cruise its almost bogging down and has no power.

We stuck an inspection camera down the intake and didnt see any oil. Some carbon deposits but nothing that would shout busted intake.

Could the cat be getting clogged? Or is the o2 causing this?

What about the MAP sensor?
 

dapepper9

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What kind of plugs were used?
Hope fuel pressure you meant 49-50 not 39-50
Bogging down at 40-50, try hitting the od off button. Does it still seem weak?
What did cyl 8 spark plug look like do you know and how does it look now?

Without blown plenum i don't clogged cat. Cats need to burn contaminants to clog and unless it's got nearly 300k miles normal exhaust won't provide that. 02 sensor is possible but in my opinion not likely. I would start with all of the above and if everything checks out you might try filling up with 91 octane fuel.
 
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Blain

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Plugs champion rc12yc

Fuel pressure was more like 39-45 vibrating between those 2 points consistantly during idle and rev

Od off seems to run way better but is also running above 2000 rpm.

Im going to pull it back in tonight and check out plug 8.

What should the fuel pressure be? I read around 40psi for 94-95
 

dodge dude94

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40 psi is correct for OBDI trucks.

Low RPM misfires are a pain to diagnose. Most are from poor quality wires or routing. I have seen a couple cases where one jug was just a hair low on compression and caused a low RPM miss.

I would think the fuel pump would only be a real issue if you were dropping pressure hard on acceleration, just cruising it would be fine or it would surge.
At this point I would verify ignition strength and move toward a compression and leak down test.
Also, how is your plenum?
 
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Blain

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I have considered getting the 8mm taylor cables, I want to look at the plug #8 again and see if its oiled up again. Didnt get a chance to tonight. I have also routed my existing wires per the TSB as well and just common sense keeping them apart from eachother.

We stuck an inspection camera down the TB and looked around, didnt see any gaps at the gasket or oil. Doesnt mean much I guess.

Im getting a sucking sound when it dies out, but uts hard to see where its coming from. Replaced pcv and IAC sensors, could just be regular noise coming thru the kn filter.

If you drive hard it climbs steadily and bangs thru the gears, od off it will cruise at 50mph just fine but revving above 2k rpm. Punch it and it will promptly kick down and start hauling again.

I fear its going to be a ring on cyl 8. The oil smells kind of gassy, and the last plug was black oiled.

Will pull tomorrow night and inspect/ re do compression and see whats up.

Im almost to the point of dropping a running 318 in and just saying to hell with it.
 

dodge dude94

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definitely inspection time, bud.

How many miles are on this engine?
 
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Blain

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Just bums me out, started with a compression test 6 months ago and everything came out 130ish.

150,000 mi
 

dodge dude94

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hmmm maybe maybe not compression, but it still wouldn't hurt.

I guess you could unplug the pre-cat O2 just for ***** to throw it in open loop and see what it does.
 
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Blain

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This is almost too embarassing to post

I pulled #8 again and it looked clean, but gassy. Had a hunch about the wires.

Pulled the summit racing ones from my 454 motorhome and started with the #8 wire.

Runs flawlessly.

Drove it 250+ miles this weekend, I'm suspecting the front driver wheel bearing for a faint ticking when I roll to a stop- but the truck towed and drove like a dream.
 

Yeret

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You say that your fuel pressure swings between 39-50 psi (which is excessive) and that you have replaced the fuel injectors and your spark plugs (or at least #8) smell gassy.

Sounds like a leaky fuel injector to me. A leaky injector will quickly bring down the fuel pressure as well as cause it's cylinder to operate excessively rich. The leak may be static in nature which can make the problem worse at operating conditions which don't require much gas (low RPM, low load).

Were the replacement injectors new or remanufactured? Also by chance, are they some fancy "4 hole" design or anything that flows more than what the OEM injectors would flow? Without a tune, you can get into a lot of trouble quickly by using "fat" injectors on a stock engine. Never mind what the ricers might say. If I had a dollar for every time that I've read of some guy selling an old "tuner" that has "Deatsch 1000cc" injectors and some "weird" rich running condition, I'd retire young. :p
 

dapepper9

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You say that your fuel pressure swings between 39-50 psi (which is excessive) and that you have replaced the fuel injectors and your spark plugs (or at least #8) smell gassy.

Sounds like a leaky fuel injector to me. A leaky injector will quickly bring down the fuel pressure as well as cause it's cylinder to operate excessively rich. The leak may be static in nature which can make the problem worse at operating conditions which don't require much gas (low RPM, low load).

Were the replacement injectors new or remanufactured? Also by chance, are they some fancy "4 hole" design or anything that flows more than what the OEM injectors would flow? Without a tune, you can get into a lot of trouble quickly by using "fat" injectors on a stock engine. Never mind what the ricers might say. If I had a dollar for every time that I've read of some guy selling an old "tuner" that has "Deatsch 1000cc" injectors and some "weird" rich running condition, I'd retire young. :p

Wire fixed his issue
 
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