7.4L MAF Issue?

[Christian Steffen]

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.

Get those damn o2s swapped lol I want to know if this is the issue or not. Sure as **** hope it works. There is nothing more frustrating than having to tow with engine issues.

When I first overhauled my truck(a couple thousand miles after the break in) I had to pull a horse trailer 360 miles and ran into a spark issue mid trip. The truck ran like ****, I got like 7-8 mpg and couldn't pull hills worth a damn, so I feel your pain.

 

[Tom P]

Get those damn o2s swapped lol I want to know if this is the issue or not. Sure as **** hope it works. There is nothing more frustrating than having to tow with engine issues.

TONIGHT! Finally gonna get it done. 24 pack of beer and some pizza, torch, welder. We are gonna burn **** and mess **** up. So Sick of it too, Christian. I bought this truck to pull **** and that's the one thing it doesn't do worth a dam. I'll post up as soon as I get it done tonight. Believe me you guys will be the first to know if this worked.

 

[Tom P]

When I first overhauled my truck(a couple thousand miles after the break in) I had to pull a horse trailer 360 miles and ran into a spark issue mid trip. The truck ran like ****, I got like 7-8 mpg and couldn't pull hills worth a damn, so I feel your pain.

What ended up being the solution to your spark issue?

 

[Christian Steffen]

What ended up being the solution to your spark issue?

It was just a bad plug wire that was letting the spark jump to random grounding points. It was just a pain because it was in the middle of a trip. Once I figured out the issue it was simple to fix.

I'm keeping my fingers crossed that this solves your problem.

 

[Tom P]

Ok I don't want to go all out and say that the problem is solved but man I really think we are there. I drove around with my foot mashed the floor and I've never felt this truck behave this way. Especially in 80 degree heat. The true test will come when I hook up to my travel trailer but as of right now we are damn near good to go.

It took the guy I work with 20 minutes. I felt like such a schmuck but it's amazing what you can get done with the right tools and a little extra torque. Oh and the sensors I pulled out of there were Bosch. Which unless you own and European car I feel like bosches are junk. Ran into the same issue in a Toyota pickup I owned a few years ago.

There's still a little bit of hesitation of the line but it could be symptoms held over from long range fuel trim. I'll keep driving and hopefully it all improves. I'll let you know as soon as I've hitched up to something significant and how that went

 

[Tom P]

Ok let's call this case closed. Did several road tests including some city and hwy towing and we appear to be in the clear. Fuel economy is through the roof. Used to get around 220 km (truck came from Canada originally and its only a 26 gallon tank) per 18-20 gallon fill up. Filled up when needle is on red. Filled the truck up last night and have done 115 km in the first quarter of this tank. Vast improvement.

I believe the O2 sensors were causing the major issue here but I didn't get the final satisfaction until the fuel filter and spark plug wires were changed and the plugs had been gapped.

Christian I believe my truck was suffering from a faulty plug wire just like yours was. More than one that I removed had a compromised outer jacket.

So for all who are curious I'll run down the list of everything done to this truck to make it right

Bosch Injector swap
New Delphi fuel pressure regulator and vacuum hose
New delco 180 degree thermostat
New wix high capacity air filter
MAF cleaned and tested
EGR cleaned and tested
Ignition switched replaced (probably unrelated but it did kill the truck)
New ignition coil
O2 sensors replaced
Spark plug wires replaced
Fuel filter replaced
Spark plugs ok, gapped from .060 to .045

I can confidently tow now not afraid the truck will crap out on me but man I wish I had about 50 more hp / ftlbs. My 2004 titan was way spunkier from a stop. 5 speed auto trans helped that though.

I'd still like to do a compression test and a fuel pressure test just to make sure I'm getting everything I can out of this tired dog. This winter it's going to have to have a top end gasket set done because it's weeping a bit of coolant from between the intake and the head. Plus I found out one of the screw ears on my distributor is broken and the cap is being held on with an oversized sheet metal screw and a prayer. So new billet distributor is on the way as well. Thanks again for your help Christian and Supercharged111. Couldn't have done it without you.

 

[df2x4]

Thanks for updating with your fix info! Seems like a lot of these threads never get truly resolved, or people never come back and update after they find the fix. Nice to see some resolution here!

 

[Tom P]

Thanks for updating with your fix info! Seems like a lot of these threads never get truly resolved, or people never come back and update after they find the fix. Nice to see some resolution here!

You bet. That's why I did it.

 

[Christian Steffen]

Ok let's call this case closed. Did several road tests including some city and hwy towing and we appear to be in the clear. Fuel economy is through the roof. Used to get around 220 km (truck came from Canada originally and its only a 26 gallon tank) per 18-20 gallon fill up. Filled up when needle is on red. Filled the truck up last night and have done 115 km in the first quarter of this tank. Vast improvement.

I believe the O2 sensors were causing the major issue here but I didn't get the final satisfaction until the fuel filter and spark plug wires were changed and the plugs had been gapped.

Christian I believe my truck was suffering from a faulty plug wire just like yours was. More than one that I removed had a compromised outer jacket.

So for all who are curious I'll run down the list of everything done to this truck to make it right

Bosch Injector swap
New Delphi fuel pressure regulator and vacuum hose
New delco 180 degree thermostat
New wix high capacity air filter
MAF cleaned and tested
EGR cleaned and tested
Ignition switched replaced (probably unrelated but it did kill the truck)
New ignition coil
O2 sensors replaced
Spark plug wires replaced
Fuel filter replaced
Spark plugs ok, gapped from .060 to .045

I can confidently tow now not afraid the truck will crap out on me but man I wish I had about 50 more hp / ftlbs. My 2004 titan was way spunkier from a stop. 5 speed auto trans helped that though.

I'd still like to do a compression test and a fuel pressure test just to make sure I'm getting everything I can out of this tired dog. This winter it's going to have to have a top end gasket set done because it's weeping a bit of coolant from between the intake and the head. Plus I found out one of the screw ears on my distributor is broken and the cap is being held on with an oversized sheet metal screw and a prayer. So new billet distributor is on the way as well. Thanks again for your help Christian and Supercharged111. Couldn't have done it without you.

Tom, glad to hear she's running better! Keep us in the loop on the results of a compression test. A tune from someone like blackbear performance or wait4meperformance would help a lot. The stock timing table is quite conservative, and getting rid of torque management makes a big difference. It would definitely be worth your money.

 

[Tom P]

Tom, glad to hear she's running better! Keep us in the loop on the results of a compression test. A tune from someone like blackbear performance or wait4meperformance would help a lot. The stock timing table is quite conservative, and getting rid of torque management makes a big difference. It would definitely be worth your money.

I know you are absolutely right. I really would love to get the tune done but I just spent a bunch of time an money getting it running right so performance upgrades are now a non funded idea. I hate the stock exhaust ~2 1/2" from manifolds to the muffler and then a 2 1/2" tail pipe is the worst setup I have ever seen before. Definitely need a better flowing muffler with a 3" tail pipe. And I don't have downstream O2 sensors so I have no way to know what shape the Cats are in. We don't do emissions testing where I live so a part of me is thinking about cutting them out and welding in a straight pipe...