I have a '95 F-150 with the 4.9L 5-spd combo. I can hear an exhaust leak which I believe to be ahead of my O2 sensor and causing my truck to run richer than it should be. It's not rich enough to foul the plugs but my average fuel economy has gone down by 3mpg over the last 6 years.

I believe the exhaust leak to be on one of the pipes where the manifold bolts together to go down toward the catalytic converter. It looks like the bolts on these connections are so rusted that even if I could get them apart, they will probably never go back together.

I'm thinking therefore that I would like to remove the manifolds entirely and install a header. This would mandate removing the EGR and AIR systems and the cat as well. My question is this.... it looks like hooker and heddman make a header for the truck, but neither says it will work for this year, no doubt for emissions reasons. Has anybody every used either of these brands, and were there any fitment issues? Secondly, when removing the EGR and the AIR systems, does anything need to be done to ensure that it does not set a service engine code?

Thanks!

 

First of all don't assume. Find the leak. More than likely your A.I.R. rail on the manifold has cracked causing your exhaust leak(a common issue on 4.9's). Secondly EFI 300 manifolds flow very well. You will not notice any improvement of power or economy by running headers and dumping your emmisions. You'll be better off saving your money by tuning up the truck and fixing the leak.

Swing by the Inline forum and do a search. This has been covered many times. Lots of good info there.

 

I appreciate the feedback and I will certainly investigate this as an option when I am taking it apart. Should, however, this not be the problem, does anybody have an answer to my actual question?

 

dont remove the egr and air system. performance gains will be dismal and youll have engine codes out the wazoo. try to fix any minor problems before molesting the motor like that. anyway, my 4.9 gets a new exhaust leak every time i fix one. first i had to replace the air rail. a short time after that i had to replace both manifolds and the gasket. now a year later the manifolds are leaking again and it sounds like a pos. does your leak sound like a tick that gets faster and higher pitched as rpms increase? you can have somebody put their foot over the tailpipe and it will make the leaks much easier to find. the exhaust manifold on these motors share a gasket with the intake manifold. so to do the exhaust manis, the intake has to come off as well. major
PITA in my opinion.

 

Wow I didn't realize they had issues with leaks. Mine is 12 miles shy of 100k. Never had an exhaust leak. Minus the many many mufflers and tail pipes short trips. Hence the 100 k on a 91. Bought new!

 

i just replaced both my fuel pumps and did it by lifting the bed, my exhaust pipes are cracked damn near completely from the cat back. dont know why seeing as i live in arizona and drive it everyday. found the whole system, cat back including muffler, from autozone for under $100.00.

 

So what I'm gathering here is that nobody knows the answer to my question.

Let me try to explain this a little bit better... the truck has 198k miles on the clock. The SOUND of the exhaust leak, although annoying, is not my primary concern. I would love it to be a simple fix but I can tell you just by looking at it that the manifolds, AIR pipe, EGR, etc, are so rusted that if they come off, they are going to do so in a thousand little bitty pieces. Now, I have a contact with a header manufacturer who can get me the headers for cost, this means that it will cost no more money to do headers than it would to buy replacement factory parts.

Installing headers may not gain me any horsepower but if I can eliminate the EGR and AIR system it will eliminate about a hundred different potential leaks, and it will clean up the engine bay significantly and open up the way for me to do other performance modifications in the future. Emissions are also not a concern because this is in the middle of becoming an off-road only vehicle. You may ask then why I even care about fuel economy, simple, even an off road vehicle needs to be at least somewhat cost effective to operate. I want to retain fuel injection for its economy, easy starting, and ability to operate fairly well under any conditions (think rock crawler)

So please, with this in mind, would somebody please answer the most important original question, which is "Is there a way to remove the AIR and EGR system and make the computer still be happy and not set a code?" I don't care if I have to trick the computer into thinking the system is still there, or somehow turning the system off by re-programming the computer. There are plenty of race cars out there that run factory fuel injection systems and don't have EGR / AIR nor do they set codes. This is because you can program the computer to not look for them. Is there a way to program these ECM's or otherwise fake it out?

 

i cant help you with exact details on removing all that egr mumbo jumbo, but i can tell you that speed density computers are much less programmable than MAF equipped cars. your truck might have a maf on it. if it does, you can probably do everything you just mentioned. if not, it will be much harder. im seeing a carb swap or a maf swap in your near future .

 

I've done a fair amount of tuning in my day and to be honest I usually prefer speed density over MAF, although MAF does have a little bit more ability to "tune itself" because it can directly measure airflow. Sometimes though using the less advanced computer is actually a good thing because it can just command something to happen and have no real feedback that it occurs. For example on speed density GM LT1 cars if you leave the vacuum solenoid that controls the EGR connected and just cap off the vacuum ports, the computer is all fat dumb and happy. I may have to see if the same trick will work here.

I tore into the truck today. I got the upper and lower intake off as well as the lower exhaust manifold piping, AIR, and EGR tubes. There is not an obvious leak in any of it. The AIR tube that injects directly into the exhaust ports could still have a leak in the bottom, I haven't taken it off yet to see.

What surprised me is the amount of gunk in the intake ports of the cylinder head. I have had the valvecover and the oil pan off and the inside of the crankcase is remarkably clean for a truck that lived on non-synthetic oil for the first 160k of it's existence. The PCV is certainly getting the crankcase vapors out of the valvecover, but it's just accumulating in the intake. Typically high quality fuel would help prevent deposits of this sort, but it looks like the design of the manifold allows the injector to spray right over the top of the deposits. This absolutely can't be helping performance any and could be a source of bad economy. Once I get it cleaned up I believe I need to install a catch can to help prevent these deposits from accumulating in the intake.

 

Okay Nathan, what's the verdict.

Did you remove the smog pump and the EGR and how does it work now?

I have a 94 4.9L with 5 speed that I want to put in my 48 Chev and I would like to remove as much unnessesary hardware as I can and still have the engine run good and get decent milage. The 48 engine bay is not as roomy as the F150.

 

I am afraid I can't answer yout question just yet. I have the header but the weather has turned too cold and wet for me to work on it. I was able to block the AIR passages on the cylinder head using some allen socket head pipe plugs. Brass was too soft and stripped immediately.

I need to get an O2 bung and vband clamp flanges welded onto my header and then have it ceramic coated. I hope to get it done this spring.

 

Can I assume these are NPT plugs? Any reason why you used those rather than 9/16-18 bolts, same thread pitch as the original fittings?

To your original unanswered questions, I can provide some real-world feedback. I have removed most of the AIR stuff although the rail and pipe remain for now, ends capped off. The EGR remains plumbed as original, though I've stuffed an aluminum foil ball in the line to reduce flow - indeed that "fixed" some low-RPM stumble issues I had. The EVAP stuff is all removed, with the exception of the relay attached to the back of the valve cover. In fact, all three(?) relays back there are still hooked up. All related vacuum lines are either removed or blocked off, as appropriate.

A couple thousand miles later, I get no CEL ever. Ironically enough, I used to get one all the time before I went down this "get rid of the clutter" path, but that may have been due to something else.

Fuel mileage is about the same before and after, roughly 18 MPG.

 

Yes the plugs I used are NPT. They may be very close to 9/16 - 18 but the original looked a lot like a pipe thread to me. Pipe threads are tapered, thus the tighter you get them, the tighter the threads seal.

Good info to know on the EGR stuff. I intend to put it back together with all the electrical portion of the EGR connected so the computer still thinks it is there, but with the passages blocked. I'm hoping the computer is stupid enough to not know the difference.

 

Nathan, you need to determine if you have speed density or MAF. In '95 it could be either one. If it's MAF, you MUST retain ALL of the emissions systems or the computer will never come out of open loop mode and your mileage will only suffer. If it's a SD remove it all just leave the solenoids on the valve cover hooked up.

 

Mine is speed density.