Hello all newbie here!
I have a 92 F150 w/300 l6 manual. I am having trouble with it loosing power as it warms up. I recently replaced the O2 sensor(again) and the coolant temperature sensor(among many others over the past year). It appears to be running rich. I also have what sounds like an exhaust leak in the engine compartment passenger side after it warms up. I do not have this exhaust leak sound when it is cold. I have had it in to ford and independent mechanics with no results. The gas milage took a dive after I replaced the engine coolant temp sending unit. Any and all assistance would be appreciated.
Thanks

 

Does the check engine light come on? If so check the codes. Also besure you replaced the right coolant temp sensor. I believe the inline 6 has two of them. One for the gauge and one for the ECM. What does the exhaust leak sound like? Is it a ticking noise while driving? That usually mean a cracked exhaust manifold or bad gasket.

-Jon

 

The light has not come on since I replaced the Engine coolant sensor and the rear antilock brake sensor last week. I disconected the Bat. , so no new codes, but I will check for the stored codes. I have had a code in the past that indicated a fault in the primary wiring for the fuel pump, but both pumps are still working? The Ford tech told me that I would't be driving if that was the case. I double checked the code after which to check my ability to count flashes.? It came out the same.

The exhaust leak sound shows up the same time as the drivabilty/lack of power symptom. It sounds like ticking, but not like tappets. I have had vehicles with exhausts that were going "out" and would say that that would be the culprit, but no evidence of any bad pipes. The trouble with trying to locate the source is that it only appears when there is a load on the engine, for example when accelerating on the freeway. Any diagnostic suggestions?

 

Just to be clear, did you replace the temp sensor on the t-stat cover/heater hose tube, or the temp sender on the pass side of the block, just below the exhaust manifold?

Either way, I'm pretty sure your exhaust leak is coming from your air injection tube. It's under the upper intake, and sends a small tube into the head at each cylinder. They are made of crappy pot metal, and they rust out very easy. The rear most tube, for some reason, is usually the first to go, which makes it extremely difficult to isolate. It also makes the noise more pronounced inside the cab. It will be loudest under load, like when the light turns green, or travelling uphill. This will create a rich condition, which will eventually clog your cats.

I'd look there first.

Take care,
~Chris

 

Yes, it was the sensor on the heater hose tube. I will check the air injection tube this morning. Is it easy to replace, or will there be a lot of swearing?
Thanks for the suggestion.
V

 

Well, I checked the codes and nothing. The Actron code reader I have indicates checking the timing. I referenced my chilton manual which said the timing could not be adjusted. I broke out the timing light anyway and could not find a typical scale or mark to reference. could someone confirm whether or not the timing can be adjusted? I found the air injection tube and felt as much of it as possible and did not discover anything obvious. Do they rot out where it screws in or on the main tube?
Thanks
V

 

The timing can be adjusted, but you must remove the spout connector first...



The timing marks are right where they should be, except on the passenger side. They can be best viewed by standing next to the fender, about where the battery is, and looking down towards the crank. It should be at 10 degrees BTDC with the spout removed.

The air injection tubes tend to fail right where the smaller tubes meet the larger tube. You won't necessarily be able to spot it at idle, though. The best way is to block the wheels, apply the e-brake, and load the engine.

The job of replacing it isn't that tough. You need to remove the upper intake, which is fairly easy. The one tool that makes the job SO MUCH EASIER is one of these!!!!! Best $20 I ever spent.

Take care,
~Chris

 

Thanks for the tips! I'll give the timing a whirl again. Is the adjustment still the same as it used to be? Do I loosen and adjust the distributor like the good ole days, or is it some high tech thing.
Thanks
V