Ask a Car Mechanic and Get Answers to Your Car Questions ASAP
Thanks for getting right back to me. Help me through this one and I'll be sure and tip well.
How can I determine for sure that it is indeed a mass airflow sensor?
Some additional info about the problem:
Last week, 2 or 3 times when I started the car it stumbled and and ran rough for 10 or 20 seconds, then smoothed right out and ran fine.
Then today when it went all out and only ran really rough, I nursed it home for 100 miles or so and the entire time the "Service Engine Soon" light was going between staying on and flashing. It seemed to not run as rough when I put it in O.D. and increased the RPM's. I thought it might be the catylectic converter or oxygen sensor (of course, I am only a casual weekend mechanic).
What are your thoughts on this?
If the MAF is dirty, the fix is easy enough: just clean or replace the MAF sensor. In many instances, the MAF sensor can be successfully cleaned by spraying the sensor element with electronics cleaner. Do not use any other type of cleaner as this may damage the sensor.
Disconnect the air inlet tube just ahead of the sensor, and then spray the electronics cleaner through the screen at the wire element in the center of the little MAF sensor. Let the cleaner soak in for several minutes, then give it another shot of cleaner. Let it sit another five minutes, then reconnect the air inlet tubing and start the engine.
If the lean codes keep coming back, the MAF sensor may have to be replaced.The mass air flow sensor can also cause the vehicle to run rough and create random misfires.
Thanks for the trouble shooting directions.
I'll test my MAF sensor tomorrow and if it turns out to be the problem, I will be sure and add bonus to my payment.
If it is not the mass airflow, could it be the catyletic or something else?
I'll be in touch tomorrow night.
Okay, so far I took out my MAF sensor and cleaned it with electrical cleaner. Re-installed it and still have the problem. I have not checked the sensor with a multi meter yet.
After I put it back together and cleared the codes, I drove the vehicle for about 10 minutes (still the same sputtering syptoms). I then checked the codes again (service engine light did not come on during myXXXXX the 2 codes I got were #4 and #7 cylinder misfire.
Based on that, do you still believe that I have a MAF sensor problem? The Navigator has 130,000 miles with the factory plugs. Could these 2 plugs be the problem? Or the EGR?
I appriciate your feedback.
Okay. I will go ahead and pick up a MAF sensor tomorrow and install it.
Evidently, the 2002 Navigator is a real project to change the spark plugs. I was quoted $600 by the shop that changes my oil. I'm told my car takes extensive labor to change out the plugs.
Do you have any shop instructions on how to get to my plugs?
Ford Excursion, Expedition, Lincoln Navigator 2000-2005
Check the plugs for deposits and wear. If they are not going to be replaced, clean the plugs thoroughly. Remember that any kind of deposit will decrease the efficiency of the plug. Plugs can be cleaned on a spark plug cleaning machine, which can sometimes be found in service stations, or you can do an acceptable job of cleaning with a stiff brush. If the plugs are cleaned, the electrodes must be filed flat. Use an ignition points file, not an emery board or the like, which will leave deposits. The electrodes must be filed perfectly flat with sharp edges; rounded edges reduce the spark plug voltage by as much as 50%.
Check spark plug gap before installation. The ground electrode (the L-shaped one connected to the body of the plug) must be parallel to the center electrode and the specified size wire gauge (please refer to the Tune-Up Specifications chart for details) must pass between the electrodes with a slight drag. NEVER adjust the gap on a used platinum type spark plug.
Always check the gap on new plugs as they are not always set correctly at the factory. Do not use a flat feeler gauge when measuring the gap on a used plug, because the reading may be inaccurate. A round-wire type gapping tool is the best way to check the gap. The correct gauge should pass through the electrode gap with a slight drag. If you're in doubt, try one size smaller and one larger. The smaller gauge should go through easily, while the larger one shouldn't go through at all. Wire gapping tools usually have a bending tool attached. Use that to adjust the side electrode until the proper distance is obtained. Absolutely never attempt to bend the center electrode. Also, be careful not to bend the side electrode too far or too often as it may weaken and break off within the engine, requiring removal of the cylinder head to retrieve it.
Okay, I cleared the codes and then installed a new MAF sensor. The problem still persist.
I drove about five miles, as soon as I started up a small hill the "Service Engine Soon" light began to flash and when I returned home and pulled the codes, I got P0171, then the P0307 and P0304.
What do I check next?
Fig. Disconnect the Coil On Plug (COP) electrical connectors
Fig. Exploded view of the coil on plugs-4.6L and 5.4L SOHC engines