Friday, April 3, 2009

Spark Plugs & the MAF

A short while ago my truck started to act abnormal. My 1996 Ford Ranger has always been very reliable and the engine has run smooth even with nearly 200,000 miles on it, but one morning it started to run very rough. After the engine started, it would jolt and shake like it was missing or the timing was off. It was so bad it would shake the entire truck, but after a mile of driving everything was back to normal. That is, until you started the truck the next time.
I probably should have tried to fix the problem right away but I slacked in my mechanic duties and let it run in its unhealthy state for about a week. I did a couple of simple checks including cleaning the MAF (Mass Air Flow) sensor The MAF is a sensor made up of a thin wire stretched across the opening of a metal ring which resides somewhere between the engine and the air filter. It measures the amount of air the engine is getting and lets the car's computer (PCM) use the correct amount of fuel to mix with the air. Sometimes bits of dust can get past a faulty air filter or carbon varnish can build up on the thin wire and lead to incorrect sensor readings and, consequently, a rough running engine.

To clean your MAF you can follow these steps (these are the steps I used for my truck but it should be similar on most vehicles).
1. Disconnect the negative cable from the battery.
2. Disconnect the electrical harness to the MAF. This should be immediately after the air filter on the air intake.
3. Remove the air inake hose from the air filter housing. Look into the hose and you should see a metal ring with a v
ery fine wire stretching the length of the inside diameter. This is the MAF sensor.4. Remove the MAF housing from the air intake hose - on the Ranger it was held on my a clamp.
5. With easier access to the MAF you can take either specialized MAF cleaner or Electronic Contact Cleaner (aerosal cans) and spray the cleaner onto the thin wire. Be careful! The wire is very delicate and if it breaks you will be spending a nice chunk of change on a new one.
6. Spray the wire several times, allowing it to dry in between sprays.
7. Reinstall in opposite order.

But, I thought this post was about spark plugs, right? It is, because cleaning the MAF did not make my truck's new and undesirable symptoms go away.
Next on my list of things to check were the spark plugs.
I had put spark plugs in the truck when I first got it about 40,000 miles ago. At the time I did not know much abou
t proper plugs and have since learned that 99% of the people who know more about car mechanics than I do that I've talked to recommend against putting Bosch spark plugs
in a Ford.

On the Ranger's 4.0L V6 engine, the three spark plugs on the driver's side are relatively easy to get to. You'll need a 3/8" ratchet with a spark plug socket and having a swivel joint and a 6-8" extension make it even easier. While you're at it, get a pair of spark plug boot pliers - they make removing the spark plug boots much easier.
Do one plug at a time so you do not mix up the wires and the cylinder firing order. When you put a new spark plug in, I like to put the spark plug into the socket first, then install it into the engine. This avoi
ds any mishaps and dropping the spark plug while trying to manauver it into position. Before reinstalling the wire boot onto the new plug, coat the inside of the boot with dialectic grease (white greasy stuff you can get from any auto parts store).

The three plugs on the passenger side are a lot harder to get at. You have to contend with the AC system and HVAC hoses.
When I got to the last spark plug (and the hardest to get to) I found this:

The center electrode had disintegrated, leaving one cylinder nonfunctional.

With all new plugs, the truck runs like new. Problem solved!

I may run some Seafoam through the engine to clean any carbon build up from the cylinder that had the fouled plug. Seafoam is a petroleum based product that can help clean the inside of your engine. Where it cleans depends on where you use it; if you put it in your gas tank it will clean the fuel injectors. If you put it in the crankcase (oil), it will clean the lower portions of the engine. To clean the upper portion of the engine (pistons, rings, valves, etc) you can add it anywhere where it will go to all cylinders evenly, like through the brake booster vacuum line.
But I think I'm getting ahead of myself, maybe I'll do a Seafoam post in the future.

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