97 F150 Almost Dies when i touch accelerator
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Senior User
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97 F150 Almost Dies when i touch accelerator
I bought a 97 F150 4x4 from a guy who had left it to die after the tranny went out. I worked a good portion of the day getting the tranny out, but the truck has another issue. It was manufactured with a 4.6. PO blew her up and put in what he said was a used 5.4 with 88K miles on it. It idles really good and sounds great until you touch the accelerator. It nearly dies then rev's high. I put fluid in the tranny and it wouldn't move in forward but would in reverse. Same thing in gear. Touch the pedal and it nearly dies then revs high! Any ideas?
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Not enough specific info.
What happens in Park or Neutral?
What happens in Drive?
Will the truck move at all?
Have you looked at codes?
Is there a CEL on or a shift lever light?.
There are several things that need to be investigated for knowledge.
1. The 4.6 did not have the same ignition hardware and layout as a 5.4.
2. Was the PCM and harness changed for this swap?
You have a lot of things floating that need to be answered because there potentially are multiple issues at the same time
Good luck..
What happens in Park or Neutral?
What happens in Drive?
Will the truck move at all?
Have you looked at codes?
Is there a CEL on or a shift lever light?.
There are several things that need to be investigated for knowledge.
1. The 4.6 did not have the same ignition hardware and layout as a 5.4.
2. Was the PCM and harness changed for this swap?
You have a lot of things floating that need to be answered because there potentially are multiple issues at the same time
Good luck..
Thread Starter
|
Senior User
Joined: Oct 2011
Posts: 485
Likes: 1
Not enough specific info.
What happens in Park or Neutral?
What happens in Drive?
Will the truck move at all?
Have you looked at codes?
Is there a CEL on or a shift lever light?.
There are several things that need to be investigated for knowledge.
1. The 4.6 did not have the same ignition hardware and layout as a 5.4.
2. Was the PCM and harness changed for this swap?
You have a lot of things floating that need to be answered because there potentially are multiple issues at the same time
Good luck..
What happens in Park or Neutral?
What happens in Drive?
Will the truck move at all?
Have you looked at codes?
Is there a CEL on or a shift lever light?.
There are several things that need to be investigated for knowledge.
1. The 4.6 did not have the same ignition hardware and layout as a 5.4.
2. Was the PCM and harness changed for this swap?
You have a lot of things floating that need to be answered because there potentially are multiple issues at the same time
Good luck..
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
The only thing that happens in Park or Neutral with the throttle is the TPS moves as the throttle plate moves.
Looks like you got a major 'hack' job to sort out.
I can't tell you even where to begin with such an issue because it's not normal for a engine to die in off idle position like this..
For thoughts; off idle adds air for the motor to accelerate, TPS and Mass add fuel and ignition timing.
Sounds like these actions are not taking place.
With this there should be codes set.
Look at it with a scanner to be sure what you have.
And again a 5.4 can't be swapped unless all the supporting hardware and control is present.
What about this? What do you have?
Good luck.
Looks like you got a major 'hack' job to sort out.
I can't tell you even where to begin with such an issue because it's not normal for a engine to die in off idle position like this..
For thoughts; off idle adds air for the motor to accelerate, TPS and Mass add fuel and ignition timing.
Sounds like these actions are not taking place.
With this there should be codes set.
Look at it with a scanner to be sure what you have.
And again a 5.4 can't be swapped unless all the supporting hardware and control is present.
What about this? What do you have?
Good luck.
Thread Starter
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Senior User
Joined: Oct 2011
Posts: 485
Likes: 1
Okay, i'll do some more investigation. i may still be able to get in touch with the guy i bought it from to ask about the harness. I read on another forum that the #'s on the valve cover will indicate 5.4 or 4.6. I also read that the plug wires were visible on the 4.6 vs. whereas the 5.4's are hidden. Don't know if there's any truth to this or not. I may wind up parting the truck out or finding another one to swap the 5.4 into if I do have a wiring harness issue. thanks! Any further help appreciated.
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
The 4.6 would normally have 2 coil packs up front with plug wires leading to each cylinder.
The 5.4 will have 8 coils over the same plug locations.
Can't mistake the difference. Plug wires vs no plug wires unless some changes were made.
You can see the harness and PCM would have to be changed to support this swap.
Good luck.
The 5.4 will have 8 coils over the same plug locations.
Can't mistake the difference. Plug wires vs no plug wires unless some changes were made.
You can see the harness and PCM would have to be changed to support this swap.
Good luck.
Thread Starter
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Senior User
Joined: Oct 2011
Posts: 485
Likes: 1
The 4.6 would normally have 2 coil packs up front with plug wires leading to each cylinder.
The 5.4 will have 8 coils over the same plug locations.
Can't mistake the difference. Plug wires vs no plug wires unless some changes were made.
You can see the harness and PCM would have to be changed to support this swap.
Good luck.
The 5.4 will have 8 coils over the same plug locations.
Can't mistake the difference. Plug wires vs no plug wires unless some changes were made.
You can see the harness and PCM would have to be changed to support this swap.
Good luck.
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Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Ok you have the 4.6L unless it's a 4.2 v6 in which case there will be 6 plug wires instead of 8.
Now return to how the system works and look into what's wrong.
First thing is to check fuel pressure with a gauge on the test port.
It must be in the 35 psi +/- range.
Obviously the motor is not getting enough fuel.
Your looking for the reason why.
Low fuel pressure, plugged fuel filter, pinched fuel line feed, faulty pump etc.
Might even be the mass air sensor not electrically plugged up in which case there would be a code set.
Remember your sorting out someone else's mess so you don't know what you will find..
Good luck.
Now return to how the system works and look into what's wrong.
First thing is to check fuel pressure with a gauge on the test port.
It must be in the 35 psi +/- range.
Obviously the motor is not getting enough fuel.
Your looking for the reason why.
Low fuel pressure, plugged fuel filter, pinched fuel line feed, faulty pump etc.
Might even be the mass air sensor not electrically plugged up in which case there would be a code set.
Remember your sorting out someone else's mess so you don't know what you will find..
Good luck.
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Thread Starter
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Senior User
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Definitely the 4.6 v8. I'll have to check all of the wiring out a bit later. I've got to rebuild the tranny first. I've tried to get the tranny out without removing the exhaust, but the cross over pipe wont let me. The truck sat for the last 4 years without being moved and has a nice orange color all over everything from the south Mississippi mud. I'm assuming that's what killed the tranny. The exhaust bolts won't budge. I've got a feeling its going to get fun when they break. I'm going to put some heat to them and see what happens.
Freshman User
Joined: Apr 2013
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Had the same RPM drop issue on my 97' 4.6. Check the condition of the rubber elbows on the pcv hose on the drivers side, runs from the valve cover to the throttle body. Also check the condition 2" or so sections of 3/8" hose on the passengers side pcv on each end of the main line, runs from the passenger valve cover to the back of the intake.
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Senior User
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Had the same RPM drop issue on my 97' 4.6. Check the condition of the rubber elbows on the pcv hose on the drivers side, runs from the valve cover to the throttle body. Also check the condition 2" or so sections of 3/8" hose on the passengers side pcv on each end of the main line, runs from the passenger valve cover to the back of the intake.
Thanks, i'll check that out. I got the tranny out an tore into it today. The forward clutch pack was toast. All of the clutch material was gone. It was steel on steel. The rubber on the accumulators were all pretty hard and the reverse servo rubber was torn. It needed a rebuild. the OD clutches looked brand new.
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