WTF is happening with my 99 4.6 AWD? HELP ME. PLS.

[98RedExp]

So I picked up another Expedition. 99 4.6 AWD.

I replaced the front diff (was blown)
Replaced Spark Plugs.
Replaced a Coil Pack.
Replaced an o2 sensor.
Replaced a the Camshaft Pos Sensor.

The passenger manifold has been replaced. The drivers side has a HUGE rotted hole in the manifold.

The mechanic was supposed to replace BOTH of them with my Pace Setter Shorty Headers but decided he didn't want to do that and just replaced one side with a stock header and didn't do the other at all.

It hard starts, like SUPER HARD. It bounces around at idle, between 500 and 1500. Sometimes it will turn right over, other times its SUPER hard to start. It has back fired both through the intake AND in the exhaust.

When driving it, thankfully only to get it towed away from scum bag mechanic, it won't get up above 55 MPH, has NO POWER driving uphill (I couldn't even drive it on to the tow truck) and drags gears out REEAAALLLLLYYYYY long. I jam it to the floor and nothing happens. Its also throwing lean codes.

When I put it in gear to move it, RPM's drop SUPER LOW and it fights to stay running or stalls. Same thing if I come to a stop.

Would the drivers side leaking manifold cause these huge problems? What else should I be looking for?

 

[98RedExp]

Anyone have some insight? I am pulling my hair out.

 

[Shabadoo]

It is possible for the exhaust leak to cause a lean condition. If enough of the exhaust gases are escaping before reaching the oxygen sensors it can skew the readings. In addition, I would check for any vacuum leaks if you haven't. These can cause the same symptoms you described.

This link has some interesting information which might help you: https://www.ericthecarguy.com/kunen...ons-Answered-Here/50573-exhaust-manifold-leak

 

[98RedExp]

Thanks Shab!

 

[Shabadoo]

My pleasure, let us know what you find

 

[docraymund]

Check fuel pressure at the rail and if you can at the pump itself before the filter. Check it at idle and at mid throttle using the ac as load.

 

[JoShing]

I had a 97f150 w the 4.6 and soundsto me like the same carp I had,so I bought a can of mass air flow sensor cleaner, fixed most of my problems right there my 01 Expo with 5.4 i use it whenever I clean my K&N

 

[98RedExp]

Done both exhuast manifolds and replaced vac lines, including the one that runs behind the intake. It idles fine sometimes, starts right up some times. Other times it really hard starts. Once put in to gear, still runs horribly. It will rev out and then die when it comes back down.

Idle Fuel pressure 34, Open Vac, 43.

What else should I be looking at.

 

[1955moose]

I'd run a dtc check. If you don't have a scanner, their relatively cheap, most shops like Midas, and repair shops will do it for you for free. Bring a pen and paper, write down any and all codes. You could have a bad mass air flow sensor, throttle position sensor, the list is endless. You need to know the basics first. Fuel pressure is fine, so you can pretty much rule out that you have a good pump, filter, up to the rails. Keep us posted what you come up with.


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[98RedExp]

Just ran the codes and there is a code for TPS. Which wasnt there before. So of course, during the removal of ****** screws, this happened.

JUST MY LUCK!!!!!!!!!!!!!!!!!

 

[1955moose]

Oh well you'll get it off. If not just replace broken part. Never ends does it!


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[98RedExp]

Update.

Replaced Spark Plugs
Replaced Coil Packs
Replaced Camshaft Sensor.
Recently Replaced MAFS
Replaced TPS
Replaced both Headers
Has new EGR Tube
EGR Recently Replaced.
Fixed Various Vac Lines.

Still starts up fine sometimes and idles OK, dies out after a long hard rev.
Other times, it hard starts and cranks hard and just BARELY starts up and then runs super rough.

Possibly a bad fuel pump? I am open to hearing suggestions at this point. I have so much time and money out, IDK what to do.

 

[1955moose]

Well as some of us old timers have stated time and time again, check fuel pressure at fuel rail. It should be at least 33 minimum. You could have a fuel pump screen that's disintegrated that's struggling to pass fuel through it. Or a weak pump that's on it's last leg. You've replaced all the other culprits. Coils, maf sensor, ran the code checks. Run a fuel test, you can probably borrow the gauge. Exaust leaks will make you lose some power, but as extreme as your problem I would say probably not. I had a 82 mustang gt with a 5.0 liter. When I had an Exaust leak it felt like I was running on 7 not 8 cylinders. But it still ran, didn't die or have your systems. Keep the faith, you've come this far.


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[98RedExp]

Well as some of us old timers have stated time and time again, check fuel pressure at fuel rail. It should be at least 33 minimum. You could have a fuel pump screen that's disintegrated that's struggling to pass fuel through it. Or a weak pump that's on it's last leg. You've replaced all the other culprits. Coils, maf sensor, ran the code checks. Run a fuel test, you can probably borrow the gauge. Exaust leaks will make you lose some power, but as extreme as your problem I would say probably not. I had a 82 mustang gt with a 5.0 liter. When I had an Exaust leak it felt like I was running on 7 not 8 cylinders. But it still ran, didn't die or have your systems. Keep the faith, you've come this far.


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The Expy is currently at my best friends and my mechanics house, 120 miles away from me. What should he do to give a proper fuel test at the rail? Edit - It also can idle completely fine after hard starting too.

I ordered an IAC, FPR, Fuel Filter and a New Fuel Pump to be there tomorrow, so hopefully we can clear things up.

 

[1955moose]

Change the fuel filter hook up gauge to Shrader valve up front on fuel rail. If your mechanic friend doesn't know what to do to get proper reading, I'd question his ability. You need to do a pressure test, both off and running. Look online to figure out how. Theirs always a how to video online.


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[1955moose]

After hooking up gauge, fire up SUV observe reading, should be 33-42 psi. Leave gauge connected, shut off see if pressure holds. If it drops more than a few pounds, theirs a leak that you guys will have to figure out. The important thing for performance is running pressure. If it's low the SUV will run lean and poor. Keep us posted.


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