'01 EB Ex V8 bogging at full throttle

[Joe Dirt]

Ok, so one of the guys that works at the place next door came over because he saw my Explorer in the parking lot. He's having a hard time trying to figure this out.

He recently replaced his upper intake after cracking it (with a new stock one) when trying to tighten down the coil pack bracket. He had the fuel rail off also. There are no fuel leaks though. (I don't know why he took it off)

Afterwards, when the truck runs, it seems to accelerate just fine if you're under, say, 75% throttle. Seems to be normal zip. IF you floor it, it kicks down the trans, the RPM's hit the kickdown level, and the truck doesn't accelerate, totally bogged down. If you back off the throttle a little, it shifts back down and goes. From where I drove it, it doesn't have a problem going highway speeds or anything, it's just that it only seems to have access to "most" of the throttle.

Checked the accel cable, kickdown cable, both are fine. Butterfly is open at full throttle. Everything is plugged in. He said that when he put the vac lines back on, he used a tree (red/green/white) from a '97 Ex, everything fit except that he had to pull the '97 rubber end that pushes onto the intake and put the one from the 2001 on there because the '97 wouldn't fit the intake tube. The FPR and EGR are hooked up to vacuum. When I had the scanner hooked to it, the throttle position was showing high enough that it should go. It seems more like it's bogged, not getting either fuel or air.

Anyone have thoughts?

 

[Tbars4]

Anyone have thoughts?

..:scratch:...I'm thinking I'll move this out of the first gen section for ya...

 

[Joe Dirt]

Good Lord... Maybe I'll figure this place out in a few years.

But, how about the stock Gen II section? (still a stock intake/stock truck if that was confusing)

 

[JCase]

Have him put a new fuel filter in and check fuel pressure. Had the same problem and it ended up being a bad fuel pump.

 

[Joe Dirt]

Need to grab a new gauge. My tester seems to have lost the adapter to screw onto the schrader valve, will try maybe on Monday. This is kind of a frustrating problem, glad it isn't mine... Ouch...

 

[2000StreetRod]

lean condition?

I normally don't comment on V8 issues since I have no first hand experience but your description sounds like a lean condition. With the age of the vehicle I would suspect low fuel pressure due to clogged fuel filter or weak fuel pump. However, since the symptoms apparently just started after the intake manifold swap I would be suspicious of that. From your original post I think:
The engine is a 2001
The replaced manifold is a new 2001 with a 1997 vacuum tree
The fuel rail is a stock 2001

Without an air/fuel ratio meter it is difficult to detect a lean condition at WOT when the PCM is in open loop and using stored tables to control the injector pulse width. There is no installed sensor that measures actual fuel flow or vacuum which needs to be done under load. The PCM adjusts the injector pulse width assuming a 65 psi fuel pressure. If the pressure is low at WOT the injected fuel will be less causing a lean mixture. If the fuel pressure is good but there is a vacuum leak the MAF sensor will measure a lower air flow than actual and the mixture will be lean. As the throttle is opened more a vacuum leak has less effect because it is fixed and a lower percentage at WOT. Vacuum leaks usually have the most effect at idle.

I agree with JCase to check the fuel pressure. Has the synchronizer been disturbed? If so, it could be out of synchronization and the fuel charge could be "stale" when the intake valves open.

 

[Joe Dirt]

Thanks Dale- you know, I called him today and he said that he did take the retainer off the cam synchronizer but did not remove the cam position sensor. But, when he put the retainer back on, the synchronizer did get pushed back down about 3/8 of an inch, so it could have indeed moved. So that could definitely be the issue... I don't have an alignment tool, is it possible to move that thing around like an old distributor to see if it changes the qualities of the truck? I think you may be on to something there... I could see fuel pressure/pump/filter and still plan to check that, but it seems really odd that this started the first start after he worked on the truck...

How much rotational movement of the sensor could cause a driveability problem? I've never replaced one so I have no previous experience...

Just talked to him again, he said that the sensor is pointed "directly forward as it was before" and the sensor itself on top was never removed for whatever that is worth...

 

[Joe Dirt]

Ok, here are the fuel pressure readings...

Idle: 64 psi

1,100: 63 psi

2,000: 60 psi

3,000: 60 psi

4,300: 54 psi

Also triggering a P0174, system too lean code.

 

[colintrax]

He should go ahead and replace the fuel filter, I have a feeling it won't fix it but it's cheap to try and considered normal maintenance.

As to the cam position sensor, it caused a miss on my 4.0 but it was low on power throughout the rpm range. Shouldn't cause it to only be low on power at upper RPMS.

 

[2000StreetRod]

P0174 System too Lean (Bank 2)

I suspect a clogged fuel filter or a weak fuel pump. My fuel pressure did not drop from 62 psi at idle to 3,000 rpm. The engine doesn't require a lot of fuel at 4,300 rpm in Park compared to WOT in drive at the same RPM. I bet if you check the long term fuel trims, the PCM will have compensated both banks for lean conditions. However, there may be two problems: weak fuel pump and leaking/unconnected vacuum line. Recheck all of the vacuum connections/hoses on the driver side.

 

[JCase]

Starting to look like a vac leak now.

Did he reuse the old upper-to-lower intake gasket?

If he did that could be the problem. Hose the gasket area down with carb cleaner (while idling and a cold engine of coarse) and see what happens.

.

 

[Joe Dirt]

Info info info... All good things to have.

Talked to him again, when he put the intake on initially, the old vac tree lines got caught between the upper and lower intake, and crushed in there. (New gasket) So, he loosened it again, and pulled them out then re-torqued it down. So, if the gasket was crushed in there, there could indeed be a vac leak. He got the '97 tree to replace the ones that were crushed. I know we re-painted our old lower/upper intake gaskets on our Mustangs back in the day and it worked fine, but he said this one had some "crush" to it out of the box so it could compress...

I just tried spraying the intake, no difference at all when running. I'll probably try the fuel filter next. Maybe it's just a bizzare coincidence that the problem starts the very first start afterwards, but hey- stuff has to break sometime.

Have to fix this- it's a personal quest now.

 

[Turdle]

This is the point of vacuum drop off,--fuel pump pressure increase.

I would check the egr and fuel pressure regulator vacuum lines are not crossed.
The EGR solenoid will turn off vacuum at full throttle. So, if the fuel pressure regulator was inadvertently connected to the switched egr vacuum, I would expect this symptom. I think it could also happen if the lines going into the egr vacuum solenoid "splitter" are switched around ( supply going to switched hole)

Does this make any sense?

 

[FIND]

My fuel pressure runs only slightly higher than that, but maybe fuel filter. Cracked or disconnected vacuum bulb? I know it would be kind of a coincidence but hey. I guess my suspicion would be a vacuum leak too. I guess there is also the outside possibility of a crack to the passenger side manifold that also was coincidentally timed. I mean, he was obviously having some sort of issues before he replaced the coil, so, perhaps the problem could have been pre-existing, but he didn't notice it when faced with his other issues.


Or do what Turdle suggested first... That sounds much more like it.

I don't think there would be a problem with the upper intake manifold as long as it hadn't been through a bunch of heat cycles. Unless the surfaces are really bad or the gasket was really over-crushed, the gasket should still squeeze back after re-torquing.

 

[JCase]

Makes sense to me but the 2001's have the fuel pressure regulator in the fuel tank. Does it even have a vacuum line going to it?

Never worked on the returnless systems before.

 

[Turdle]

Yes, the returnless systems still have a vacuum fed "dampener" on the fuel rail.

 

[JCase]

Alrighty. Thanks Turdle.

 

[Joe Dirt]

Ok- this is interesting... Like I said before, he had to put the 2001 Splitter that plugs into the bottom of the intake vacuum port onto the 1997 vac tree. If there are 2 holes on the splitter (one for red, one for white) it would make a difference which one is plugged into which hole on the splitter? I would have figured that both holes would run vacuum from the splitter. Shows how much I know... Will have to have him swap the lines...

 

[Turdle]

Yeah--that!!

 

[Joe Dirt]

Ok, tried that, still the same issue. He pulled the splitter off the bottom of the rear of the intake, and swapped the lines to the other holes on the rubber splitter. Same issue...

I'm thinking that we need to check that tree, or is it a possibility that the EGR vacuum regulator is bad? Should I swap the lines on there, are they in different locations on the part in 97 vs 01?