It's late on a Friday afternoon, and I've got my hands full. In one bay is a Caravan with its dash peeled back, waiting for
an evaporator core. In my other bay is an Eclipse with its block on a stand and its guts on my workbench. Out of the corner
of my eye, I see my service writer coming.
"Pete, I know you're slammed, but I have a customer who is heading out of town, and needs his car looked at," the service
writer says. "He says it isn't running right, and he's afraid of breaking down on his trip. Can you help me out?"
I've been in this business long enough to know that you are either too busy or not busy enough. I also know it's important
to take care of your customers – or someone else will. Of course I'll take a look at it. So I walked up front with my advisor
to see what we had.
LET'S TAKE A RIDEUp front, the customer and his 2001 Ford Explorer were waiting. I asked him to take a ride with me and tell me what the symptoms
were. We got in the car, and the rough idle complaint was obvious. It was a little rough, but not severe.
I also noted that there was no Malfunction Indicator Lamp (MIL) on. I asked him when he first noticed the rough running, and
he told me it just started that morning after returning home from the local store. Because he was leaving with his family
for a long weekend in the morning, he didn't want to take any chances that there was something seriously wrong.
I turned out of the drive onto the main road that runs by our shop. Our location allows an easy test drive route that has
city driving on the first half and highway driving on the second half. Normal city driving didn't reveal anything abnormal,
but I did notice that the engine smoothed out off idle. The next symptom showed itself as I accelerated onto the on ramp to
the freeway: The engine skipped a beat under load. Again, nothing severe, but certainly not normal.
When we returned to the shop, I dropped my customer off at the waiting area and asked him to give me a few minutes to check
it out.
IN THE BAY
I pulled in behind the Caravan and grabbed my scanner. Just because the MIL wasn't on didn't mean the Engine Control Module
(ECM) didn't have anything to tell me. I went in using Enhanced Ford mode to see what, if any, codes were stored or pending.
This check showed nothing.
The next area I checked was current data. When I check current data, I like to take a look at the listed Parameter Identifications
(PIDs) to see if anything stands out. With the key on and the engine not running, I saw that the barometric pressure (BARO)
PID was off, reading 150 Hz and 27.03 in/Hg. My town is just about sea level, and normal BARO for us is 157 to 159 Hz and
29.90 to 29.98 in/Hg. This may or may not be related, so I just made a mental note of it for now.
Figure 1 This scanner screen capture shows BARO and fuel trims. Notice the BARO PID.
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The next place I checked was the fuel trims at idle and 2,500 rpm. I wanted to know if the ECM established fuel control and
to get an idea if there is anything that is causing the ECM to make corrections outside of normal ranges. Figure 1 illustrates
what I saw at idle. Note again that BARO is out of range.
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