Rough Idle, Poor Mileage, Studdering when accelerating

JAKESEEBACH

MEMBER
FORD RANGER

I have a 1997 Ranger 4x4 with the 4.0 ltr V6, manual transmission 130K miles.

I have replaced the MAF (mass air flow) sensor, cleaned the K&N air filter, replaced the fuel filter, checked the spark plugs and wires and replaced the Idler Control Valve. I did all of this because the Check Engine light came on and when I had it checked out, AutoZone told me that it was the MAF sensor. After I replaced and checked all of the above, the Check Engine light came back on.

The idle is fine for a few minutes, regardless of the engine being warm or cold, and then turns very rough. The engine will die on occasion. If it does die, it will restart but will die again if left idling or after pressing the gas. If I drive around for a little bit, the idle will either return to normal or be very high.

Does anyone have any ideas?

Thank you.

5 Replies

MERLIN2021

MECHANIC
17,250 POSTS

Can you remember the code(s)? MAP EGR and fuel delivery all can do this. Lets nail it down before you spend all your money.

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Saturday, November 17th, 2007 AT 4:56 PM

JAKESEEBACH

MEMBER
4 POSTS

There are two codes. The first one is the following with the possible causes.

TROUBLESHOOTING PO171

DEFINITION: Fuel trim bank one condition.

EXPLANATION: The powertrain control module uses the oxygen sensor to calculate the air/fuel ratio of the engine. The computer has recognized a ruch or lean condition on one engine bank only.

PROBABLE CAUSES:
1. If bank one and two codes set together suspect fuel pressure of MAF (Mass Air Flow) Sensor.
2. Oxygen sensor defective.
3. Ignition misfire-repair.
4. Fuel injector problem.

The second one is as follows with the possible causes.

TROUBLESHOOTING PO174

DEFINITION: Fuel trim bank two condition

EXPLANATION: The ECM has detected a rich or lean air/fuel ration condition on engine bank two.

PROBABLE CAUSES:

1. If bank one and two are set together suspect a fuel condition or MAF sensor fault.
2. Failed HO2S21
3. Ignition misfire condition
4. Fuel injector problem
5. Engine mechanical condition.

Some more background.

I had not changed the fuel filter nor cleaned the air filter since I got the vehicle (about 100,000 miles ago). I was told (by an apparent retard and then I listened which makes me a retard) that neither needed to be cleaned nor changed. After changing both, I ran a fuel system cleaner/fuel injector cleaner through the tank. I have about 1/4 of the tank of gas left with the cleaner in it. I was told that since it had been so long since I changed the fuel filter, that the injectors will most likely fill up with junk the fuel cleaner will get loose. Is this more B/S or what?