Lazarus-F150

I have a 92 5-speed manual 4x4 with the 4.9L motor and I have been having some hesitation during acceleration at all speeds for a while now. She's idling just fine. I just replaced the fuel pump and there is no change. From the reading that I have been doing it sounds like it may be a faulty oxygen sensor and/or throttle position sensor. I have also had the truck tuned up recently, which included new cap, wires, and plugs. Any thoughts?

If you agree, any recommendations on oxygen sensor brand? I don't mind paying a little more for something that will work better and last longer. I have heard some good things about Bosch, but I am also considering the Motorcraft replacement.

Thanks for any suggestions that you can give!

crazzywolfie

anyone? i am in a similar situation and the oxygen sensor is on the list of stuff that i am pretty sure needs to be replaced. i am just not sure what brand or or model number would be good for the 4.9 with 5 speed. would the NTK Part # 22503 work good? i know on my dodge NTK is what is recommended but ford might be a bit different.

GMtraitor

Did this happen after tune up? Any codes? Check ur spark plug gaps

crazzywolfie

i am almost wondering if the issue is related to a bad map sensor. poor acceleration is one of the symptoms of a bad MAP sensor.

Lazarus-F150

My truck is an old farm truck that I am trying to get back into shape. After a tune-up, lots of Seafoam, and a new fuel pump it is much better, but still has some hesitation issues while driving. The idle is smooth at ~1000RPM, which I have heard is a little high. The engine speed also takes a few seconds to return to idle after putting the clutch in and letting off the throttle while driving. As a result, I am thinking that the throttle position sensor may be involved.

After reading a bunch of posts, it sounds like there are a bunch of sensors that could be part of the problem.

Thanks!

Lazarus-F150

Do you know how to test the MAP sensor?

Thanks!

crazzywolfie

from what i found while searching it sounds like you need a expensive multi meter that can read Hertz Frequency to test the map sensor.
http://troubleshootmyvehicle.com/for...e-map-sensor-1

Lazarus-F150

Update:

I disconnected the green vacuum line to the EGR valve and the truck drives much better; however, there are still some hesitation issues. Also, I now notice that once the engine is warm it sometimes idles around 1500RPM and sometimes at around 1000RPM.

Any thoughts?

Thanks!

crazzywolfie

i am almost to the point where i am thinking about spending $100 and ordering a TPS, MAP and o2 senor from rock auto. then i got all things covered. o2 sensors are suppose to be changed every 90k miles or so anyway but most people don't change them until they start running into issues. i don't know about the other sensors.

Lazarus-F150

My replacement O2 and TPS sensors arrived yesterday and I am hoping to have the time to install at least the TPS tomorrow. I will post the results when I have the chance to get the swap done and do a little driving. Also, to answer your earlier question about O2 sensor brand, I have heard good things about Bosch sensors (part #15719), which is the brand that I bought from Rock Auto.

If you are going to buy any/all from Rock Auto, then here is a discount code that will save you 5%. It may not be much, but its a little savings at least.

1800366715424204