I have a recently acquired 1996 F150 with a 4.9L / 5 speed . The truck has 175,000 miles and seems to be in very good mechanical and cosmetic condition . My problem is twofold ! It has no power and tends to overheat when put in a load situation .I have replaced the plugs and wires , the O2 sensor past the cat , and the distributor cap and rotor .I also cleaned the Throttle body , MAF sensor , and the IAC sensor . It does run better but still no power when put in a load , such as going up a hill ! If you drive around on level ground it runs about midway on the heat gauge , unless you turn on the AC . This will cause it to start to heat up past midrange on the gauge and to boil over onto the ground when you park and shut it off . The strange thing is I just let the truck idle in my driveway for 10 minutes and the gauge never got past midway on the gauge . So I thought perhaps the extra strain from the AC is causing the extra heat so I turned the AC on ( still idling in the driveway ) and let it run for 15 minutes at idle . The heat gauge never moved past midway for that 15 minutes ? I have suspected a faulty fan clutch but this questions that theory ? If it idles , for that length of time in my driveway , and doesn't overheat then I'm doubting the clutch is bad ? Also , the engine idle sometimes hovers around 1100 rpms , when you stop ( i.e.- at a red light ) for maybe 10 seconds then drops down to about 800 rpm's . Could the TPS be a factor in the condition discussed ? What else could be causing this ? Timing , or ....what ? All help will be truly appreciated !

 

have you considered the cats, if their clogged it would cause the truck to strain and overheat from the extra work

 

Could be right, it's much more common than people think.

If yours are just bolted on, try unhooking them and see if it makes any difference. The more work the truck is doing, the more exhaust needs to pass through. If they're somewhat plugged, the increased flow can cause problems.

Out of curiosity, what gears do you have?

 

It's a standard cab 1996 F150 SWB with a 4.9L , AC , and a 5 speed . Would the cats being partially clogged cause the low power yet allow it to run at idle with no obvious problem as well as the overheating problem when the engine is under load compared to idling in the driveway ? I replaced the O2 sensor because of the " check engine " light being on at time of purchase . The code showed a problem with the one after the cat. converter. I'm basically an illiterate when it comes to any newer model ( computerized ) vehicle ! Too many sensors , too much wiring , too many special tools and needed special knowledge to work on them ! They certainly don't make them like they used to ! Hopefully with your help , I'll get this " thang " fixed ! Thanks guys ! P.S. - I just now went out and checked the tag in the door frame and it lists the axle as " 18 " which according to the vin decoder ( at the top of the forum page ) is a 3:08 non-LS !

 

I had a Nissan pickup for a little while that would do basically what you describe with the overheating. I tried the fan clutch and the thermostat as well before I finally pulled the head off. Turned out to be a blown head gasket, but it was just blown enough that it caused no other trouble but the overheating and bubbles in the coolant surge tank. No coolant in the oil or anything else.

I also had a Jeep Wrangler that had your lack of power problem. It turned out to be a bad cat conv. Didn't have the overheating thing, though. Just the lack of power. Replaced the cat conv. and power came back.

 

If the truck has 2 cats, then just eliminate one, if state emissions law will let. I did the same thing to my '92 F-150, I6, 5 spd. Front cat was ok, second(rear) cat was warped and fused together. If the age is consistent with mileage, it may be a clear cut case of a bad cat as described earlier by others.

As you stated the O2 sensor was faulting and resulted in a code, then it may be worth a couple more bucks to cut between the 2(may be possible or not to get in a spot where you can see either one from the opposing end of the cut) and inspect. If the mixture had been running rather rich for an extended amount of time, it can and has been known to damage a cat, and/or severly shorten the lifespan of it. Another reason, with only a small percentage of shorter lifespans of a "CAT", is the use of motor oil with higher than normal Zinc in it/and other elements for fighting metal to metal grind. This has been supported by many as the leading role in motor oil, since at the time the vehicle was new, higher Zinc was acceptable to prevent nasty cold, dry starts. But as we constantly try to improve the "wheel" we inadvertantly forget the PAST million vehicles on the road that still needed a good amount Zinc, since they weren't designed with such tight clearances, or newly redesigned engines, resulting in much more efficient, cleaner vehicles, needing only like 5w-20.


I got way off topic, but a reputable muffler shop can assist if you decide to cut one out and just put a piece of straight pipe if you can salvage either cat.

 

Makes sense what youre saying Timbersteel but a muffler shop will not cut off a cat. Ive been down that road and the multiple shops I went to told me all they can do is put it together like factory.. Even if I was to come in without anything after the manifold they would not replace anything without replacing it as stock.

If you get lucky you may find a shop that will cut corners but odds are most of them will be jerks about it.

 

The one thing you don't want to do is randomly replace parts. It will be expensive, frustrating, and probably not solve the problem.
Once you get used to the computerized engine, you will appreciate it. The computer can help you figure out what is wrong. Even if the check engine light is not on, the computer can still have codes stored that will help find the problem. The 4.9 normally has plenty of power. You axle is good for fuel economy, but not so good for putting power to the road or pulling any serious weight.
The first thing to do is pull the codes, and come back here with the results. Here is one way to pull the codes: http://fordfuelinjection.com/?p=13
Stored codes can be read any time. The engine running codes need to be read while the engine is up to temp. Reading codes on a cold engine will give a long list of codes, because the sensors are not hot enough yet.
Often a code will take some thought as to what is actually wrong. It is not as simple as replacing the sensor giving the code. I like to erase the codes by unhooking the battery for 20 minutes then take it for a drive. It takes a few minutes for the computer to relearn how to manage the fuel again, and it may idle bad, and run rough for a short time. Then I pull the codes, and know that any codes present are current and not something stored for a long time.
A basic tune up is almost always a good thing to get out of the way. Plugs, wires, air filter, and timing. Be sure and check the base timing with the spout connector out. Improper timing can kill power, and if it is off far enough, can cause overheating problems.
Many problems like partially clogged cats can be diagnosed with a vacuum gauge. This is a lot easier and quicker than pulling a cat off. You can read how to do this here : http://www.secondchancegarage.com/public/186.cfm
If working on an overheating issue. I think the first step is a new and tested thermostat. Get a new thermostat in the factory temp range, cooler is not better. Put the new stat in a pan of water on the stove. Use a cooking thermometer to test the temp where it opens. New stats have been known to be bad too. Really creates a problem when you put one in assuming it is good.
To do what I have described, you are needing just basic hand tools, a timing light, and a vacuum gauge. If you are going to keep you truck running great, the timing light and vacuum gauge are basic tools also.
The 4.9 is well known for lasting a long time. It can easily outlast the body and tranny, and present very few problems. Seriously overheat any engine and all bets are off on how long it will last.
Good Luck Frank

 

a clogged cat will cause exactly what your saying. lost power and in turn overheating

 

Could be the cats , i would do a preasure test on the cooling system to make sure it holds pressure & check the radiator cap & thermostate , how long has it been sence the cooling system has be serviced , flushed ect .... Lew

 

Check out your cats and test the temp sender, but I would also recommend doing a complete flush of the cooling system. This means removing the antifreeze plugs in the block, thermostat, and draining the radiator. If you have a way to hook a hose up to your kitchen or other faucet, use HOT water to flush it out. Flush the block from the thermostat housing for at least 5 minutes and flush the radiator for the same amount of time.

My pick up had problems regulating heat, especially during the summer- after eliminating the sender unit as a suspect, I did a complete flush of the system and haven't had a problem since. You'd be surprised how much gunk can build up in the system.

 

On the cat issue, if you can eliminate 1 cat, most muffler and inspection shops are completely fine on the issue. It's just certain states require that you have 1. Mine doesn't mind, so I cut between the 2 and inspected, and that's how I came to see that one cat was destroyed. I simply purchased a new cat and had both removed and installed the new one in the OE spot right below the exhaust manifold.

And yes, Muffler guys can be real jerks and terrible welders! Been there and wont' go to another one again that sell's "Monkey" welds!!

As dbgrif stated, I did the same with a Prestone flush kit, but removed the Thermostat and reused the old gasket to prevent leakage. The gasket itself is only like $1.00. I then bolted the housing back up and hooked the garden hose up to it, but not full blast. Just a gentle flow with someone helping. Once I got in, I had my assisstant turn the water on and I started it. I ran it for about 15 to 20 mins, from idle to 2000rpms and then gently back down, with the same cycle every few mins. When I shut the engine off, I had my assistant turn the water off and then water for the rest of the water to empty from the filler neck hose that was hooked to even longer hose that emptied into the street. I purged the system with some compressed air and filled it back up with 50/50 mix. About 12 quarts is what mine took.

 

Guys , I appreciate your help ! I haven't had the chance yet to check out the cat ( s ) ! Can anyone tell me why the truck appears to have two cats on it ? Is the second one ( to the rear ) a cat also or a resonator or ...? I'm new to F150's and I'm a little lost at the moment ! I do remember ( from looking underneath at an earlier time ) that the first cat and the second cat ( ? ) almost appear to be one unit connected by a seamless connection . Can they be separated for replacement or do you have to replace them as a unit ? My questions make it obvious that this is all new to me and I hope I don't come off as an idiot ? This truck seems to be a solid truck ( other than the posted problems ) and I look forward to getting it right where it can be enjoyed ! Again , thanks !