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Discussion Starter #1 (Edited)
HELP! 2007 Taurus - Transmission Shift hiccup from 1st gear to 2nd gear

Hi all - I'm new to posting in the forum, but I've referred to this place a lot over the years for help with repair and maintenance.

I currently have an issue that I have not been able to diagnose/repair and was hoping for some help.

I have a 2007 Taurus with 136,000 miles. About a month ago - when the engine is warm - it started to have this hiccup (best description) that happens just after it shifts from 1st to 2nd gear. No lights or codes are on or available. My first thought was I had a transmission issue starting, and since it had been 60,000 since the last transmission fluid/filter change, I took it in to Certified Transmission for a diagnosis and service. They said the transmission looked fantastic and the jerk I was noticing was most likely due to needing a tune-up, as they said they noticed a slight "miss". But the transmission itself got a clean bill of health.

My hunch was it might be the VSS (Vehicle Speed Sensor) so we changed that and it ran fine for about day. So then I thought maybe we got a bad VSS (aftermarket) so we replaced it again. Same thing. Ran fine for almost 2 days, then started acting up again. So I thought we would try a Motorcraft VSS. Same result. We also changed the Cams Sensor (but not the synchronizer) and replaced the plugs and wires.

We have a code reader that runs Bluetooth to an android phone - no codes - and when driving the vehicle used it to graph the acceleration. When we charted it, there would be a steady incline until it would hiccup just after shifting into 2nd then it would have a small sudden drop (looked like a “V”) on the graph and then continue to accelerate. All other shifts from 2nd to 3rd and from 3rd to 4th and OD performed normally without a hiccup.

We only get this little slip at the start of 2nd gear.

Any ideas or suggestions as to what we might try next? Anyone experience the same or similar issue?

Thanks for your input!
 

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Discussion Starter #2
Addendum:

We tried resetting the PCM by disconnecting the battery overnight. There were no shifting issues under regular commuting driving conditions for almost 48 hours then it started again. Any suggestions as to what to try next? We are stumped.

Thanks!
 

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I’ve been scouring this forum for ideas on what it may be and how to fix it. We replaced the VSS twice – worked for two days each time then started doing it again. We replaced the Neutral Safety Switch – and it has worked for a week with no issue, then started doing it again today. When I reset the PCM by disconnecting the battery, it will work for a day or two then start acting up again. Transmission was recently serviced and received a clean bill of health. I’d sure like to know what the issue is. It has to be a sensor or something similar if it will stop doing it when the PCM is reset. Any other ideas?
 

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HELP! 2007 Taurus - Transmission Shift hiccup from 1st gear to 2nd gear

Hi all - I'm new to posting in the forum, but I've referred to this place a lot over the years for help with repair and maintenance.

I currently have an issue that I have not been able to diagnose/repair and was hoping for some help.

I have a 2007 Taurus with 136,000 miles. About a month ago - when the engine is warm - it started to have this hiccup (best description) that happens just after it shifts from 1st to 2nd gear. No lights or codes are on or available. My first thought was I had a transmission issue starting, and since it had been 60,000 since the last transmission fluid/filter change, I took it in to Certified Transmission for a diagnosis and service. They said the transmission looked fantastic and the jerk I was noticing was most likely due to needing a tune-up, as they said they noticed a slight "miss". But the transmission itself got a clean bill of health.

My hunch was it might be the VSS (Vehicle Speed Sensor) so we changed that and it ran fine for about day. So then I thought maybe we got a bad VSS (aftermarket) so we replaced it again. Same thing. Ran fine for almost 2 days, then started acting up again. So I thought we would try a Motorcraft VSS. Same result. We also changed the Cams Sensor (but not the synchronizer) and replaced the plugs and wires.

We have a code reader that runs Bluetooth to an android phone - no codes - and when driving the vehicle used it to graph the acceleration. When we charted it, there would be a steady incline until it would hiccup just after shifting into 2nd then it would have a small sudden drop (looked like a “V”) on the graph and then continue to accelerate. All other shifts from 2nd to 3rd and from 3rd to 4th and OD performed normally without a hiccup.

We only get this little slip at the start of 2nd gear.

Any ideas or suggestions as to what we might try next? Anyone experience the same or similar issue?

Thanks for your input!
 

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Missfires are often misdiagnosed as transmission problems. Check the coil pack for any cracks, especially on the bottom. If ANY cracks are found, replace the coil pack with Motorcraft or BWD ONLY. When ware the plugs and plug wires last replaced?

If the speedometer works, there is no problem with the VSS as the speedo uses the VSS signal as well as the PCM.

Most modern drivetrains use "torque mamagement" which momentairly reduces torque during shifts by retarding ignition timing to limit tranny wear and tear. Ignition system issues sometimes rear their ugly head during this process.
 

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Missfires are often misdiagnosed as transmission problems. Check the coil pack for any cracks, especially on the bottom. If ANY cracks are found, replace the coil pack with Motorcraft or BWD ONLY. When ware the plugs and plug wires last replaced?

If the speedometer works, there is no problem with the VSS as the speedo uses the VSS signal as well as the PCM.

Most modern drivetrains use "torque mamagement" which momentairly reduces torque during shifts by retarding ignition timing to limit tranny wear and tear. Ignition system issues sometimes rear their ugly head during this process.
I am having intermittent bumpy upshift; vanishes then comes back, often disappears after a run, shut down, then a hot start. A replacement alternator seemed to half-cure the problem.

I'm wondering if it's a tricky ignition wire; or a poor battery not holding amps after shutdown for many hours. The problem is definitely 'on-off' and not a slow change of performance over a drive. This feels electrical. What's your take on it?
 

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Battery is really only used to start the engine. After start, the high amp alternators in modern cars will take care of 100% of the cars electrical load, assuming, of course, the alternator is operating as designed.

Measure system voltage with engine running and no electrical loads. Should be around 14.2V or a little higher after a cold start, and drop to 13.7 to 14 V after several minutes with engine at 2000 RPM. Turn on high amp draw accessories like all lights, rear defrost, blower on high etc with engine at 2000 RPM. System voltage should drop by a half a volt max. If the voltages are in range there is nothing wrong with the charging system.

If the batt is not holding a charge, you will have slow or no crank.
 
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