Took Eric’s advice; saw odd RPMs on Ford Freestar

[Scott]

Hi everyone, I’m new to the forums, but am going to enjoy hanging out here. I’m a DIY guy who spends a good part of the day on YouTube and then under the hood in the evening just exploring and learning. I used to run an electronic repair shop, and now I’m learning about cars. My real job is a principal at a school.

First the car: 2005 Ford Freestar SEL, 4.2L, automatic transmission, AdvanceTrac, stock (no mods)

The van had some weird “buck” that would happen while driving. I seem to have eliminated that by finding a faulty wire on the alternator connection. I just mention it for full disclosure.

I’ve also done the Ford TSB on the wet PCM, resealed it per FordTechMakuloko’s videos several months ago. I called Ford and they already did the torque converter recall before I bought it.

I took Eric’s advice on scan tools and watch live data as we’re driving and the car is running well. The other day I was playing around with values as my wife was driving. I was having fun, it is a great way to learn and find more topics to learn about. On that trip I started looking at RPM. What I saw were some spikes that were showing up on the data scan (BlueDriver) but not on the tachometer or how the engine drove. Had I not seen it on the scan tool I never would have known it was happening.

I attached the data file (in .pdf) and highlighted all the times it happened; it’s big but you can move through and look for the highlighted areas. I was only looking at three parameters on that drive (Engine Load, RPM, and TPS position). Sometimes it happened for just a second, sometimes for several seconds. The engine would be cruising along (never happened at idle) at 1600-1900 RPM and the scan tool would tell me it was momentarily jumping to around 4000 RPM. Like I said, the tach and the car did nothing to make me think anything was wrong. Just a normal trip back from the library.

Additionally, the Mode 6 data gives me an error on TID 56 00, which after some looking around is “potential misfire events” as reported by the crank position sensor. I may be wrong on that, I’m still learning.

My first inclination is to think there’s something wrong with the crank position sensor, because of the reported RPM spikes, and maybe something from the Mode 6 data. But I’m still learning, so I thought I’d ask the experts before I just start swapping out parts.

Would you go ahead and change the crank sensor, or would do more tests for verification, or would you look somewhere else, or is this just normal?

Thanks for any help or direction you can give!

Attachments:

• DataLog-Mar_11_2017_4-02-14-PM.pdf

Topic

[college man]

i would not change anything at the moment. I would wait for a problem to show.

[zero]

Generally a misfire code will only be set when a certain number of misfires in a given time frame are detected. So Mode 6 may be saying ‘hey, there’s a couple of misfires but nothing extraneous’. On tech level scan tools there are counters for total misfires and each cylinder, you can watch the numbers go up and then reset themselves only to cycle again.

If you don’t have a CEL I wouldn’t start throwing parts at it like beads during Mardi Gras.

[Author]

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