7.4L MAF Issue?

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my name is alex

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Upgraded to the Bosch 4 Hole style. Also installed a delphi fuel pressure regulator and replaced the vacuum hose between the FPR and intake. Incredible fuel economy increase. Went from average of 9 to probably close to 12-15mpg. Will know more at next fill up. Plugs cap and rotor were done right before I purchased... P/O's were chasing the ignition interlock module issue (ignition key security or whatever you really call it) and I have a receipt from the shop that did the work.

Again it only happens when the truck is hot. I would assume injector issue or plug wire cap/rotor issue would present 100% of the time.

One thing leading me to MAF issue is the P/O's had installed a K&N air filter (drop in not cold air kit) and I noticed when changing it the intake tube was oily and smelled like gas, which I assume is from the injector and FPR issue? Pulled the KN and installed a dry paper element.

I need to fix my hot start issue as well, and I'd love to get an MPG increase as well. Where did you get your injectors and FPR?
 

Christian Steffen

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This would explain why I didn't notice any hesitation before I replaced the faulty thermostat. O2 sensors it is then. I've read the downstream sensors send signals but do not influence the tune of the engine? Other than the possibility of throwing a code what is the reason for this?

That is correct, the downstreams are just a check that the cats are functioning. Mine have been deleted for years.
 

Tom P

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I need to fix my hot start issue as well, and I'd love to get an MPG increase as well. Where did you get your injectors and FPR?

I got the FPR off of Amazon, and the Bosch injectors off of eBay. I would highly recommend doing distributor cap and rotor while you're in there. Also a great time to drain the coolant and replace the thermostat, because its nice to have the upper rad hose out of the way. You'll need new plenum gaskets (amazon as well). Take your time with this job. The injectors can be a pain to remove from the fuel rail, and hooking the fuel lines back up to the rail is a true test in patience. Learn from my hassle that the fuel lines re install easier when the rail is completely bolted down. I thought having some wiggle room would help but that was not at all the case. Also replace the vacuum hose from the FPR to the intake. Consider putting clamps on it, to keep it tight and prevent future leaks.

If your injectors aren't slobbering like mine were, then I can't really say that you are going to see a huge increase. 3 or 4 of the intake runners on mine were black. At best I was getting 9 mpg, and now, I'm getting a more realistic 12-13. And I'm assuming that issue caused my O2 sensor issue as well. This thing was a bit of a basket case when I bought it but I knew that going into the purcahse. Its a great truck for all intents and purposes and I'm hoping to get it running properly soon because I've got a family camping trip coming up and this will be the first time loading up the family and hitting the road with our travel trailer. Some day I'd like to do a complete tear down on the engine, but for now we are cobbling with parts.
 

my name is alex

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Thanks for the tips Tom. I'm going to have this done at a shop (one of these days) as it's not something I have the time/patience/skill to do myself. I plan on bringing my own parts though.
 

Tom P

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Went to get started on the O2 sensors and they are stuck tight. They look dam near original and the corrosion around them is frightening. Ive sprayed them with penetrating fluid and then started and ran the truck for 60 seconds to let the pipes warm up and hopefully let the fluid seep in. I bought an o2 sensor socket in an attempt to do this properly. Drivers side is very accessible and gives lots of room, however the passenger side there is only one angle to get at it and its not forgiving at all.

So now I'm faced with a dilemma... Friday morning I'm leaving on a camping trip which is 460 miles round trip. The last thing I want to do is accidentally disable my truck 2 days before I'm supposed to leave.
 

Tom P

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After driving for a bit yesterday with the o2 sensors unplugged, I think I may try that route for the trip and worry about replacing them after I get back. The truck did throw a CEL after about 15 minutes on the road but the hesitation and stutter issue was gone. There is a pretty good little shop next door to where I work and I know the owner. I may give him a call and see about having him replace the sensors for me. They've got lifts and proper tools.
 

Supercharged111

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One way to check (depending on how they failed) is to floor it unless there's a PE delay, don't recall. Anyway, if the truck sees PE mode it'll richen itself up and, for me, take off like nothing's wrong. Same with unplugging.
 

Tom P

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Well, we just got back from our trip yesterday and I'd have to say this truck is like Jekyl/Hyde. I started the journey with the O2 sensors unplugged hoping that perhaps I'd see some improvement.... not the case. Some times it could pull a hill rather reasonably, and other time it would stutter and act rather gutless. It hesitated at almost every stop. I'm thinking about pulling the EGR valve off and checking it for carbon build up. Any way to test it? Don't want to throw a $120 replacement at it if its not the issue.

One way to check (depending on how they failed) is to floor it unless there's a PE delay, don't recall. Anyway, if the truck sees PE mode it'll richen itself up and, for me, take off like nothing's wrong. Same with unplugging.
You'll have to pardon my ignorance, what is a PE delay?

I lied about my mileage too. I thought I was getting around 12+ MPG but I did that math forgetting that my Odometer was in KM (purchased from Canada) and I'm really only getting about 8, closer to 9 hwy. Wondering if the bad EGR could kill mileage too?
 

Tom P

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Still looking for an answer. I cannot get the O2 sensors out. Purchased an O2 sensor socket and soaked the sensors in Kroil (penetrating fluid) to no avail. I don't want to ape on them and break them and end up in a massive world of hurt because I have no proof that these are the issue. Truck still fires up great and runs good cold. Sucks when I'm towing. I picked up my brother in law's tractor last night and towed it home (15 miles one way). Truck ran ok on the way out there empty and then slowly deteriorated on the drive home to the point I could barely get up to 50mph on the last leg of the journey. I've been reading up on anything I can find that deals with this hesitation/loss of power/crappy fuel mileage problem that seems to plague this engine and so far everyone who's solved their issue's solution is different from everyone else. What a gremlin factory.

Two new discoveries/possibilities that I am going to try tonight. My truck has had some witchcraft done to the battery cables and when the truck warms (or when the alternator has charged the battery back to full after starting) the voltage drops to below 14. I know that 13+ volts should still be plenty to run the truck but I'm going to check and improve grounding contacts, just to make sure. I'm also going to replace my Ignition coil. Its one of the few components that will deteriorate performance wise due to heat. Plus the issue has been getting progressively worse. I'm leaving on another long camping trip soon, but this time I'm pulling two mountain passes and will be driving in much hotter conditions, something this truck hates.
 
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