Rough idling and poor fuel economy on 92ford f-150

A vacuum leak in the intake manifold of a 2000 Ford F150 4x4 with a 4.6L engine and automatic transmission can cause a range of symptoms, including:

1. Rough idle: A vacuum leak can cause the engine to run rough at idle, which may be especially noticeable when stopped at a red light or stop sign.
2. Misfires: The engine may misfire or hesitate under load, such as when accelerating or climbing a hill.
3. Poor fuel economy: A vacuum leak can cause the engine to run lean, which can result in decreased fuel economy.
4. Check engine light: A vacuum leak can trigger a check engine light, which may indicate a code related to the engine's fuel system.
5. Stalling: In some cases, a vacuum leak can cause the engine to stall or die, especially at idle or when coming to a stop.
6. Hissing sound: A vacuum leak may cause a hissing sound to be audible from the engine compartment, especially if the leak is large or near the intake manifold.

If you suspect a vacuum leak, it's important to have it diagnosed and repaired as soon as possible, as it can cause damage to other engine components over time if left untreated. A mechanic can perform a smoke test or other diagnostic procedures to locate the source of the leak and repair it as needed.

Oil pressure light came on 3 or 4 times during our 5 minute test drive The engine is worn out, a new motor will exceed the value of car.

Vacuum leak. Just idles less rough in gear. Could be time for a tune up. Bad engine/transmission mounts will also cause more vibration.

I had the same problem on my 2001 Sunfire (same car as the Cavalier-different branding) which I was able to fix successfully.

My symptoms were:
-Traction Control OFF light illuminated
-Cooling fan running even if engine cold and it was freezing outside (I also noticed that when the Traction light illuminated, the fan would then begin)
-Rough idle with black smoke when cold
-Poor fuel economy


I have a code reader which produced codes P0130 and P0171. These are error codes for the upstream oxygen sensor (the one under the hood).

I simply replaced the O2 sensor (it took me 10 minutes). I did not reset the check engine light after the repair as I wanted to see what the car would do on its own. The idle was much smoother with no smoke and the cooling fan stopped running unnecessarily. After 1/2 mile down the road, the Trac light went away and the system functioned normally. I tested this by trying to accelerate quickly up a snowy driveway. I also noticed that the acceleration and shifting (auto tranny) were smoother. I reset the check engine light. All is satisfactory.


What was happening to the car before the repair:

P0130 is usually for a bad O2 sensor and P0171 is the sensor detected that the motor was running too lean (but it actually wasn't-the sensor was essentially giving a false lean signal).
The rough idle, black smoke, and poor economy are due to running too rich. In my case, the sensor told the PCM (the car's computer) that the air/fuel mixture was too lean. In response, the computer said "OK, more gas!" That's why it ran rich. This was evidenced on the old O2 sensor as well...it was completely caked with carbon from an excessively rich mixture. This further destroyed the performance of the O2 sensor.

Check the firing order, The push rod has 2 differnent sizes for intake and exhaust, If they get switch you get the rough idle

Hi, Try to replace fuel filter. It maybe clogged up and making engine run rough or poor. Also check and replace spark plugs. A bad spark plug will make it run rough too. Good luck.

Possible Idle air control, simple to change on the throttle body

One suggestion:
Speed sensor failure.

Info:
Some of the classic symptoms, stalling at dead stops. failure to auto lock doors. poor fuel economy. Failure to go to overdrive.


Recommendation:
Go to your local parts store and run the failure codes.

Shop notes:
Your ECU thinks that the engine is running with out moving, During slow down the engine steps down the idle to match ground speed and as a result the engine will not stall. At present it goes directly to idle and stalls due to drag on motor.
Hope this tip helps.

R/
David

first you need to find out why the light is on go to auto zone or advance auto parts they do it for free.

if your exhaust system is not up to factory spec this will cause idle and rough running conditions,as well as the poor fuel economy, this is due to the sensors not getting accurate readings and sending skewed info to the onboard computer, (the exhaust system has as many as 3 sensors, although i think yours has only one, if you can also remove the catylitic converter, you will get more power./better fuel economy