7.4L MAF Issue?

Christian Steffen · Jun 28, 2017

Tom P said:
Not yet. Haven't had a chance when the truck was cold to actually start pulling plugs. I will check that this weekend though.

Finally got a chance to change my coil last night and some interesting things happened. First, the truck seems to be running better albeit far from what I would expect. Even in when the truck made it to Closed Loop, I still had enough power to almost spin the tires going around a corner. Truck does have locking diff though. Second, I got both the HRT and the O2S readings on my code reader to check out. Then the scanner popped a Pending DTC of P0131 which said low voltage in O2SB1S1. Checked the live data and saw .000. Confirming the original diagnosis. Still planning on swapping them out Friday after work. I don't want to get my hopes up that changing these stupid things are going to give me more power. I suppose thats all possible but I drove our shops 1997 C3500 flatbed towing the same tractor and trailer that i was towing when my truck stranded me. This truck has a Vortec 350 but easily did better than my 454 in its current state. Hoping that by the time we are said and done here, I'll run circles around the shop truck.

I hope that is the issue then, definitely keep us posted. It really shouldn't even be a comparison between the two. Unless the C3500 has numerically higher gears?

Tom P · Jun 28, 2017

Christian Steffen said:
I hope that is the issue then, definitely keep us posted. It really shouldn't even be a comparison between the two. Unless the C3500 has numerically higher gears?

Will do. As far as I know the shop truck has 4.11 like mine. Has 100,000 less miles than my truck though. Going to gap my plugs down to .045 tonight. I noticed every plug available for this truck is factory gapped at .060. What would you recommend for plugs if I have to replace them? I'm not sold on iridiums because theyre expensive as hell and you cant gap them anyway. The guy who built my boat motor drag races on the weekend and he swears by the standard copper delco's because they are adjustable and can be run over an over.

Tom P · Jun 28, 2017

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Ok here's a pretty good snapshot at what 5 out of the 8 plugs look like. This probably being the ugliest of them. I quit trying to get the back three because I effed up a wire and had to stop and fix it. Truck is running but I'm doing new plug wires before I go. The ones that are on there are junk 7mm anyway. I gapped what I could down to .045.

These are NGK V power plugs

Christian Steffen · Jun 29, 2017

I don't see any issues with the plugs you have. I'm pretty sure I'm running those NGKs, are they iridium? If so, then they're what I have.

Christian Steffen · Jun 29, 2017

NGK TR55IX?

Tom P · Jun 29, 2017

They are NGK TR55. No iridium. You cant gap iridium plugs (or at least you really aren't supposed to). I've read forum post after forum post and article after article about what the best type of plug is (E3's anyone? :head3:

). I think what a lot of people forget is that the other components in their ignition system ie cap rotor wires coils etc... probably have more to do with the spark your vehicle makes than the plug itself. Sure you may not get 100,000 miles out of a set of copper core plugs but when was the last time I put 100k on a rig? never. Why spend 8 bucks + when I can go buy quality Delco or NGK's for $1.50 and you'd probably need an engine dyno to tell the difference, if any. Especially on a bone stock 170K mile truck?

Sorry I'm rambling. Not changing the O2 sensors until tomorrow night so I'm trying to fill the void in my life. Not really sure how I'm going to feel if swapping the sensors out solves my issue? I love a good mystery, almost more than I love solving them.

Christian Steffen · Jun 29, 2017

Tom P said:
They are NGK TR55. No iridium. You cant gap iridium plugs (or at least you really aren't supposed to). I've read forum post after forum post and article after article about what the best type of plug is (E3's anyone? ). I think what a lot of people forget is that the other components in their ignition system ie cap rotor wires coils etc... probably have more to do with the spark your vehicle makes than the plug itself. Sure you may not get 100,000 miles out of a set of copper core plugs but when was the last time I put 100k on a rig? never. Why spend 8 bucks + when I can go buy quality Delco or NGK's for $1.50 and you'd probably need an engine dyno to tell the difference, if any. Especially on a bone stock 170K mile truck?

Sorry I'm rambling. Not changing the O2 sensors until tomorrow night so I'm trying to fill the void in my life. Not really sure how I'm going to feel if swapping the sensors out solves my issue? I love a good mystery, almost more than I love solving them.

I hear ya, I don't know how much of a difference the expensive plugs make. And you can gap them, you just have to bend the strap or at least that is what I did. I haven't had any issues running up to 5k.

Either way the plugs you have are fine.

What? · Jun 29, 2017

MAPP gas, heat the hell out of the oxygen sensor thread. Circulate the heat so it isn't in one spot. That's going to get it out. It'll be in one piece or broken. Good news is exhaust shop can weld new o2 sensor bung cheap. Shouldn't be more than $40 for labor/material per bung.

Even better if you can find a local Welder and you just remove the exhaust and bring to him/her.

Tom P · Jun 29, 2017

What? said:
Even better if you can find a local Welder and you just remove the exhaust and bring to him/her.

Thanks for the tip but if you saw the connections and hardware on my exhaust, you'd know id be better off with a sawzall... There is some truck underneath all my rust haha

We are going to get the torch and the welder out. Worst comes to worse we weld a big ass nut over top of it and us a bigger wrench to bust it free.

Tom P · Jun 29, 2017

Well I finally put the truck over the edge tonight. Honest to goodness lit up on the dash check engine light popped up tonight. I was towing my boat to the lake. Started out great until the truck warmed up again. After about 10 miles I got the stutter and hesitation. Noticed the CEL and plugged the scanner in. Beeps and red flashing lights all over the place. O2 sensor fault. At that point I switched over to live data and under fuel system it said Closed loop-fault. Truck ran a little bit better after the fault code popped because the truck shut off the O2 sensor system but still what I would call limp mode. Better but I'd hate to stay in that predicament. I hope the new sensors really do fix me up. It would be nice to see closer to 12mpg rather than 8.

7.4L MAF Issue?

Christian Steffen

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