We have a 2002 F-150 4.6L 4x4. The engine went bad and we bought a new engine (remanned ATK). Had this engine installed and a year later it was bad and was determined it was a manufacturer defect so they sent a replacement engine under warranty.

We had this new engine installed. The mechanic fired it up and it backfired through the intake. They claim that the compression is good, the fuel pressure is good, and the timing is correct. Can they check these things when the truck is not running? Anyone have any ideas?? The mechanic is not very helpful as he is completely frustrated with the situtation...

Everything I read leads to a timing issue but they say they checked it so before I go in there screaming I want to make sure it couldn't possibly be anything else... PLEASE HELP!!!

 

sounds like timing to me

 

Could be a camshaft went flat, or a follower fell out, or a stuck valve.............Remanned engine.........I'd be looking for another mechanic..............He should diagnose it....thats his job.

 

Ok so I camped out at the mechanic all morning today and here is what I know...
1) when they received the new (remanned) engine the cylinder heads were dirty
2) the place where the water pump goes was not threaded
3)cams appear to be ground down

The mechanic is saying that the cams are 7.4 degress and they shoudl 6.5 degrees he says that they are the correct Cams for a 4.6L engine just not this particular engine. Does that make sense?

So now the engine manufactuere (ATK) is out for the holiday and I have to wait until Tuesday to see what they say.... UGH!!

 

I wouldnt believe that the cams are not for that 4.6.........I dont believe your mechanic knows what he is talking about. it should run fine if the camshafts are in time, and the rebuilder doesnt make the camshafts, he just buys them. I believe in your case, you have a poorly rebuilt engine, and an incompetent mechanic.=a bad situation all around.

 

i agree, any cam would work in the motor and startup... might not have full power or RPM, but would start. If it backfires thru the intake either the cam chain is not timed so the valves open and close at the right time, or the ignition timing is off and the spark is firing at the wrong time. Do you have a cam shaft position sensor bad ??

 

Been having same issue here. Got 2000 F150 7700 with 5.4 and this engine was rebuilt a while ago. It was swapped from and Expedition of same year. It was running rough after guy swapped it. So I checked it and fuel pressure is at 35 idle, and raises around 40 when revving. After turning off, fuel pressure holds at 35 and slowly drops overtime. Found several bad coils and replaced them. I also had to disconnect the cats cause driver side is completely plugged.

Well I finally got everything ready to start again. I go to start and still have to flood clear it but it started up. Sounded to have slight miss at idle but revved fine. Revved few more times then loud bang and it stalled. It backfired and blew pcv tube right off manifold. I put it back on and tried again, and fired without flood clearing (didn't start up) then backfired through intake blowing pcv tube off again.

I can't think what's causing this. It has never thrown a code for misfires or any code to help. All it throws is a p0453 due to pressure sensor on tank being bad. Previous mechanic broke it removing tank. I'm fairly stumped how a good running engine just suddenly won't unless previous mechanic got into something he shouldn't have.

 

I know this isn't going to help much here but for the rest:
The engine control system is very complex,. Unless one knows a lot about how it all functions, you get into these jams and it becomes a nightmare and very costly before it's all over.
.
On this situation, the engine vendor has not offered a quality product, the shop is not supposed to 'have' to trouble shoot the product but only support the service needed on the install but he does have to recognize certain issues.
Backfire in the intake is purely the ignition firing a cylinder before the intake valve closes. Since the fuel injectors are outside the cylinders and keep injecting gas as the engine is cranked one 'incedent' sets off any others that have injected gas because the intake is common to all cylinders.
Ever see a AAA fuel dragster blow to top off a motor from missfire and hydro lock?
For this to happen the camshafts have not been timed properly at assembly.
To add to the issue, fuel injection and ignition timing are dictated by the cam position sensor on the driver's side head.
You can see now what can happen if the cams are not timed properly, the sensor is also out of timing.
Don't do it, but my 'thinking' is it's base ball bat time on some body, for the mess.
Now you see why everyone has to be competent.
Good luck.

 

pretty much the truth..............and This is also why I hate these cheap remanned engines......the quality isnt there.......Ive replaced one engine in my trucks, and I either rebuilt it myself, or I put a used engine in....I put a used 4.2 in a 97 F-150, and that was over 3 years ago, I no longer own the truck, but its still going......

 

Even if you know a lot about the systems, it can still be a nightmare to figure these issues out. I understand the systems, and followed down the lines to do the repair. It made no sense to me why it would run great beyond 2500rpms, but miss and stumble horribly down low and not throw a code. But after sitting and thinking about it after posting, I realized one thing, stuck valves.

I tore valve cover off, and three rocker arms were laying in the head and a lifter. I pulled some used, but good lifters, from another engine to see if could get it to run. Well found the valves have to be bent cause even with the cam tightened down, I could slide the rockers right on and have a huge gap to cam lobe. So that explains why when I changed that one coil, it finally got spark to that cylinder and kept backfiring blowing pcv tube off. Needless to say, the quick engine swap he had in mind with two other mechanics ends with me finding issue 8 months after it began. Seems I made more progress in two days then they did in months. Guess I will either be building him a new engine or going to Jasper.

 

It is always difficult to get a clear picture...when when paint is already been on the canvas.

It is refreshing to know that are some who are willing to step up to the plate for issues that are not entirely self started...that is how you build customer relations.

Annap13
I'd be on the phone with this place where the remanned engines are coming from...& demand satisfaction. Parts coming all dirty and holes not complete....not a good sign if the simple stuff is over looked then what about the critical work being done?? Obvious that they don't care about quality and craftsmanship! ...if they give you grief demand you money back...& go else where.

 

And get a different mechanic.

 

Hi everyone!
I wanted to give an update...
So I "demanded satisfaction" from the ATK engine people. They are now shipping me a new engine and will pay all the labor in the current engine is in fact not functioning due to a manufacturer defect... I also have the mechanic (who swears it is the engine) covering the labor in case it was not the engine adn it was something they did.

Apparenlty the whole 6.5 degree thing was incorrect. I went to the shop today and I saw what they were talking about.... the issue is that the Lobe Lift Intake is 7.4mm (.028 in) which is consistent with a 5.4L engine. I have a 4.6L which should be 6.5mm (.025in) Does that make more sense?

Either way new engine on its way hopefully we can get this one installed and running correctly!! Thank you all for your words of wisdom!!

 

So here is another update to my ongoing saga...
The people at ATK sent a new engine the mechanic installed it and now they are having the same issue... it's backfiring through the intake again... ARE YOU KIDDING ME???

I am at a loss... I already had to pay $4K to the mechanic... and they still can't get this truck working. Any ideas on what to do??

 

Has the ECM or engine computer been checked and verified good??
and all sensors...especially the cam position and crank shaft position

old school tells me this is a timing issue... hints of like 180* off??

defiantly don't pay anyone any more until this is running. & you're satisfied