So after some work under the hood, I am still suffering from a bogging issue that I am sure is heat/humidity related. It appears to only bog down during the day when it's warm and when it's humid. Any other time, it doesn't do it and runs really good. But as soon as it gets over 78* or so, it can barely move and requires flooring it in every gear to get it to go.

EDIT - This occured before I did any work to the truck as well.. even before the new exhaust.

New -
Timing belt
Water pump
Thermostat & all hoses
Head gasket (only did because I had the kit and had it torn down for the belt)

Fuel pump was replaced before I bought the truck, has proper pressure at the rail. No check engine light. Replaced the O2 sensors and exhaust 2 years ago so it's not the converter.

I am personally thinking it's a failing sensor that hasn't triggered a check engine light yet. I was assuming either the MAF, intake air temp sensor or coolant temp sensor for the EEC.

Any ideas?

 

This vehicle has OBD-2 so its difficult to believe no CEL is lit. The CEL isn't burned out, it does light up for its self check at KOEO....right???? Have you scanned the computer for any stored pending trouble code clues that haven't happened often, or long enough to aggravate the computer to light up the CEL????

If you have a scan tool that can read & display live PID's, plug it in & have it take a look at fuel trim, fuel injector pulse width, O2 sensor & MAF sensor response & TPS sensor response.

If no joy there, since it seems to be temperature & humidity sensitive, maybe perform a wet down test with a spray bottle of water, of each plug, wire & coilpack, at warm idle, after dark, while looking for a arcs & sparks light show.
If no joy there, unbolt & lift the coil packs & inspect closely for cracks underneath that they are known to do, as that could cause high voltage electrical leakage, or arcing to ground & a wimpy spark. Or lift them a little & spray under there to see if you can induce break down with the engine at idle.
Don't forget to inspect the plug boots & spark plug external insulators for carbon track signs of flash over, or cracks in the plug insulators, which the wet down test should aggravate enough to cause the arc & spark light show.
Some thoughts for consideration, let us know how it goes.

 

Oops, forgot to mention that it has new wires and coils as well. Plugs only have about 3,000 miles on them. As for CEL, it does work and hasn't came on at all except for an EVAP leak that I fixed 2 months ago. No stored codes, either.

My Dad does agree that I need to borrow a scantool with live data to see what the deal is.

 

OK, good feedback, sounds like the problem is something the computer isn't monitoring & it's occurring Only at temps over 78F is a good clue but I can't for the life of me figure where this piece of the puzzle fits just yet.
Since you don't have a scan tool, that can read & display live data, maybe the inexpensive ELM scantool running FORScan or the like software to the viewing device of your choice as discussed here https://www.ford-trucks.com/forums/1...-scantool.html may fit your needs, as it can scan All the vehicle computer/controllers & monitor & display up to 19 live data feeds at once on its dash board, so you could view & monitor a large number of suspects at once, to see if any are obviously acting out, or are border line. This kind or electronic trouble shooting is Way faster & more accurate than trying to back probe suspects with a multimeter, or swapping suspect parts.
Let us know how it goes.

 

While your waiting on a scan tool, make sure all the basics are right, like battery charge is up to snuff, the alternator is outputting under load & at hot temps, B+ & B- connections at the battery posts, body & engine ground contacts are clean bright & tight, the B+ cable connection to the under hood power distribution center is clean & tight & the fuse & power relays sockets inside the distribution box are clean bright & tight & without corrosion. Once your satisfied all the basics are sound, proceed with under hood thump & wiggle tests on suspect electrical connectors & connections & wiring harness runs.
In the early morning before its warm, try warming suspects with a hair dryer or heat gun, to see if you can induce the problem.
to confirm, once its warm enough to act out, try cooling the suspect & see if the problem will clear. More thoughts for pondering.
Keep us posted on your trouble shoot.

 

Thanks for the suggestion. Being a computer nerd, I should have thought of a Bluetooth OBD2 scantool in the first place. Went ahead and found a genuine ELM327 on eBay and bought one. Should have it in 2-3 days and will report back with the results.

New Bafx ELM327 Bluetooth OBD 2 Can V1 5 Scan Tool Android OBD Reader Scanner | eBay

As for battery connections and grounds, I cleaned the snot out of them when I did the head gasket so they are all clean and tight.

 

Ok, while waiting for the ELM, have a look at fuel pressure again with your fuel pressure gauge, when its acting out. Also perform a fuel volume over time test when its acting out, it should be something like 1/2pt in 15 seconds. Post up the numbers.
When its acting out, using your analog multi-meter, have a look at how smooth the TPS sensor resistance changes when you slowly go from closed to WOT.
If all that checks out, have the ELM scan tool take a look at the MAF & upstream/before cat converter O2 sensor PID's, to see how they're behaving when its acting out. Fuel trim will tattle on vacuum, or fuel feed problems. Misfire codes can isolate cylinders to check spark & fuel injector problems. You can have a listen to the fuel injectors with a stethoscope, or one fashioned from a length of tubing, or hose, wooden dowel, long screwdriver, one end on the suspect, the other to your ear while listening for one that sounds different that the others, or in time with engine roughness or miss.

 

check my thread i just posted about fuel pump filter deterioration. talk about an a-ha moment. pull the fuel pump from top of tank and inspect the filter if it is still even there. apparently they deteriorate after 10 or so years and causes power loss and bogging after running about half an hour. where all fuel tests and sensor tests pass, with no CEL. this was my problem and i guarantee its more common than just me. good luck !

 

Forever and a day later.. I finally got the ELM327. It got lost in the mail and was supposed to be here last Wednesday. As for the fuel strainer filter, it, the pump and the sending unit were replaced right before I got the truck.

pawpaw, here is a video of the live data after being driven for 15 minutes. As far as I can tell, everything appears to be fine. At first the TPS percentage worried me, but I guess it's supposed to be around 16% at idle.

https://www.youtube.com/watch?v=NbV_...ature=youtu.be

 

OK, so have you had the ELM hooked up & running when its acted out, so the ELM can get a snapshot of what was out of order when it acts out???

 

My friend came over today and we hooked up the ELM and I drove around while he watched. Nothing appears to be abnormal at all except the exhaust smells a little bit when it bogs down (typical bad smell from running rich, the egg smell). We even hooked the fuel pressure gauge up while driving and the fuel pressure doesn't change much at all. Stays steady in the normal range.

I am going to chalk this whole thing up to a bad injector or 2. I noticed when I pulled the rail when I was working on it last month, I found that 2 of the injectors had wet tips and some wetness in those runners. I thought it was most likely normal but I guess not. Gonna buy a complete set of good, matched injectors and will post results whenever I get them.

 

Are you saying the ELM didn't find fuel trim out of whack when it bogged down & no set trouble codes????

 

Oops, forgot to mention after the bogging and smell that the O2 readout showed the mixture was rich. When it runs fine, the numbers are low. He thinks it's errant or shorted out injectors that do what they want to when they want.

 

OK, that's good feedback. So, were Both cylinder banks indicating rich???

 

Finally downloaded a screen capture app on my tablet to record some driving live data. To me, it seems like it's running a bit rich at times according to the O2 sensor voltages. You will have to go full screen to read the text.

I think it's supposed to range between 0.1 and 0.6 for driving and anything over that is considered rich. Not sure. All I know is when it spikes to 0.8-0.9, the exhaust starts to smell rich and the converter starts to stink.