97 5.0 issues

[lugnut1009]

Pulled the intake today. Couldn’t find any leaks or anything at all wrong. Blew out and cleaned everything. Took off passenger side valve cover since it’s the worst side. No problems there. Did another compression test on that side with valve cover off and all plugs out. Still 150 psig on all. Sure thought I’d find a smoking gun here. Even pulled the ECU just to look for bad parts, all looked new inside.

 

[1998Exp]

View attachment 423945Pulled the intake today. Couldn’t find any leaks or anything at all wrong. Blew out and cleaned everything. Took off passenger side valve cover since it’s the worst side. No problems there. Did another compression test on that side with valve cover off and all plugs out. Still 150 psig on all. Sure thought I’d find a smoking gun here. Even pulled the ECU just to look for bad parts, all looked new inside.

With the valve cover off it may make some sense to check for a timing chain issue. Both valves on cyl #1 should be completely closed on compression stroke when the harmonic balance is indicating TDC. If you are on the passenger side, it's probably #6, but not absolutely sure.

 

[Justinwht]

O2 readings are high, which if I understand correctly indicated a lean condition and adding fuel. And the O2 graphs are cycling up and down and not flat lined so they’re working

Though it may not apply in this case, I just want to throw this out about O2 readings. P0170 - P0172, especially P0171 - System Too Lean.
That would point to insufficient fuel feed but if you reword it, it can mean too much air feed. That would indicate a vacuum leak sucking in more air after the MAF sensor is assuming there is.

 

[C420sailor]

I’d take a good hard look at ignition. We tend to take that for granted on these trucks. We change the plugs, wires, coils, and assume everything is good.

I worked on a 5.4 triton recently that was throwing lean codes, wouldn’t throw a misfire. Fuel trims were absolutely ripping (high). It was desperately trying to dump fuel in.

Two of the COP coils were shot. Those jugs were moving nothing but air and raw fuel. The O2 sensors saw all that air as a lean condition, and tried to compensate with lots of fuel.

 

[lugnut1009]

Does anybody have a good wiring diagram? Curious about my O2 sensor wiring vs sensor wiring, and the wiring at the coils. I’ve gone over spark plug wires and locations multiple times but need to make sure I have a good ground to the block and just curious of what the wiring is in general.

Used this for spark plug wiring:

 

[410Fortune]

This is correct 5.0 firing order

Lean code
Too much air in the system, the computer has attempted to compensate by adding fuel abs was not able to overcome the lean code

Lean condition can be caused by low fuel pressure, bad injector, or by un metered air, any air entering the intakes after the mass air flow sensor

Check the intake plumbing really well
No evidence of leaks at the intake plenum gasket where it meets lower intake?

I would not be suspecting wiring with those codes unless something jumps out at you on the wiring side of things

Looking at the picture you posted above there is a lot of black dirt/ soot on that lower intake where the gasket was.. it should be shiny metal, looks like a leaky gasket no?

 

[lugnut1009]

This is correct 5.0 firing order

Lean code
Too much air in the system, the computer has attempted to compensate by adding fuel abs was not able to overcome the lean code

Lean condition can be caused by low fuel pressure, bad injector, or by un metered air, any air entering the intakes after the mass air flow sensor

Check the intake plumbing really well
No evidence of leaks at the intake plenum gasket where it meets lower intake?

I would not be suspecting wiring with those codes unless something jumps out at you on the wiring side of things

Looking at the picture you posted above there is a lot of black dirt/ soot on that lower intake where the gasket was.. it should be shiny metal, looks like a leaky gasket no?

A lot of that was RTV sealant from the previous owner. I haven't found any vacuum or intake leaks at all. I put the intake back on yesterday and my next plan of attack is to use a temp gun and see which cylinder is cold when running by shooting the exhaust manifolds right at the heads. My theory now is possibly a failed or plugged injector. Which would explain a miss and the excess air in the exhaust. All of them look to be the factory yellow 19# injectors, the part number on the side of them is F6VE-A5A.

 

[Mbrooks420]

I’d suspect whatever he goobered with RTV.

 

[lugnut1009]

Well since I can never remember to borrow one from work, I went to harbor freight and bought a temp gun. Cranked it up and shot each individual head pipe leaving the head, and looks like 1, 5, and 7 are cold. Guess that narrows it down to fuel or spark!

 

[410Fortune]

You could have pulled all 8 injectors and bench test/ clean them quite easily

I followed a YouTube video years ago and made an injector tester cleaner using an old tire valve stem and some jbweld. Also cut off an old injector wiring pigtail Now I am able to run carb cleaner through an injector as I open and close it with a jumper
Box or car battery. I can see each injector spray and run cleaner through them. I have rehab many injectors this way. I do this to every used injector before they go into my engine projects. It has become a valuable tool.

There should be no silicon on the upper plenum gasket!!!! Just a dry gasket

The intake elbow gasket and throttle body gaskets should also be checked, it is quite common for the elbow gasket to blow out over time leaving you with large air leak

 

[lugnut1009]

You could have pulled all 8 injectors and bench test/ clean them quite easily

I followed a YouTube video years ago and made an injector tester cleaner using an old tire valve stem and some jbweld. Also cut off an old injector wiring pigtail Now I am able to run carb cleaner through an injector as I open and close it with a jumper
Box or car battery. I can see each injector spray and run cleaner through them. I have rehab many injectors this way. I do this to every used injector before they go into my engine projects. It has become a valuable tool.

There should be no silicon on the upper plenum gasket!!!! Just a dry gasket

The intake elbow gasket and throttle body gaskets should also be checked, it is quite common for the elbow gasket to blow out over time leaving you with large air leak

I have seen the videos testing them before, and I should have pulled them if for nothing else just to inspect. But I have a test kit and another gasket on the way. So I’ll pull the intake, again, and test them all. Also I want to inspect that big wire bundle that goes right beside the EGR valve to see if I have any bad wires in there going to them.

 

[410Fortune]

Get a valve stem, carb cleaner red straw and some in weld make the tool now so the job weld has time to cure

 

[lugnut1009]

Get a valve stem, carb cleaner red straw and some in weld make the tool now so the job weld has time to cure

Already purchased a tool to do this with so no need to fabricate one. Thanks for the heads up though.

 

[lugnut1009]

UPDATE!!

My injector tester came in today. So I pulled the intake back off and the injectors. Testing the injectors with this tool was an eye opener. It has one setting that pulses the injector coil like the ECU does. I was able to find several that were partial plugged or sticking maybe, and one completely dead. I’ve ordered an o-ring kit for the working 7 and 1 replacement injector.

Also see a coolant leak that I think may be coming from the lower intake gasket? It’s to the drivers side of the thermostat and behind the water pump. Don’t know what else it could be, plus I have the new gaskets for it. So might as well tackle that while I’m waiting on my injector.

 

[lugnut1009]

By the way if anyone is interested, this is the test kit I bought: ALLOSUN Fuel Injector Tester &... Amazon product ASIN B07VC37VRB
I had to fabricate some smaller wire connections to properly connect to the injector, but other than that I’m happy with it.

 

[EB4X]

GREAT NEWS!! .... Always great to finally get to the bottom of a headache/ mystery !

 

[410Fortune]

Coolant leak could be
the timing cover gasket?

The water pump weep hole can spit coolant when water pump gets old

There is coolant temp sensor to the drivers side of the thermostat also

Or lower intake like you said. The front two bolts of the lower intake enter the water jacket. If you did not put sealant on those
Bolts (thread sealant or anti seize) coolant can seep past

Consider a coolant system pressure tester if you need to pinpoint

Well done on the injectors!!! A set of 8 reman is not expensive
Replacing one is fine too just make sure it’s a Bosch

 

[gadawg30124]

Not even in open loop at initial startup? I thought the 2nd set of O2’s were only measuring the efficiency of the cats. I wouldn’t have removed them, but I got it this way.

Also I’ve checked the EGR valve, it’s operating properly, and purchased a new IAC valve, waiting on the throttle body mounting gasket before I put all that back on.

Don’t listen to that guy. All 5 of my 5.0 trucks are custom exhaust without cats. As long as both front 02s are present your just fine

 

[gadawg30124]

Did you disable the Bank 1 and bank 2 O2 sensors after the non existent CATs? Also remove the DTCs for those O2 Sensors. This way your fuel trims should reference the 2 existing O2 sensors. I would expect to see a noticable improvement. Sometimes people just take the CATS off and expect a miracle to happen when it comes to performance. They don't realize it is all tied together in the program. Best of luck.

 

[gadawg30124]

Did you disable the Bank 1 and bank 2 O2 sensors after the non existent CATs? Also remove the DTCs for those O2 Sensors. This way your fuel trims should reference the 2 existing O2 sensors. I would expect to see a noticable improvement. Sometimes people just take the CATS off and expect a miracle to happen when it comes to performance. They don't realize it is all tied together in the program. Best of luck.

Stop posting incorrect info, you can in fact drive just fine without cats and a tune. All 5 of my explorers prove that. The pre o2s are required for fuel and air the post are only there for cat functions. That’s your o2 lesson of the day. Thanks for trying. A miracle does happen you gain power and free flowing exhaust and the rears are not tied to fuel trim