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Feels like it is starting in second gear

Tiny
DUCATIMN
  • MEMBER
  • 1995 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 153,000 MILES
From a stop my truck feels like it is starting in second gear. This happened about 2 months ago and then was fine till last night. When on the freeway doing 70mph I lost speed to about 55mph then the trans down shifted till I was back to 70. This happened repeatedly for a few miles. Then at the next stop sign felt like it was starting in 2nd gear like before, this continued off and ob till I was home. This morning everything was working fine again. Any ideas, that hopefully don't involve me laying under the truck removing the trans?

The trans does not seem to be slipping and the engine seems to be running fine.
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Thursday, September 24th, 2009 AT 11:26 AM

11 Replies

Tiny
RACEFAN966
  • MECHANIC
  • 5,029 POSTS
OK yes I have two ideas that do not involve transmission overhaul. The TPS (Throttle Position Sensor) and the VSS (Vehicle Speed Sensor). The TPS and the VSS can both be tested with a digital multi meter. So if you have one or can find one to use then I can walk you throught he tests on both. The tps is on the throttle body 3 wires and the VSS is on the rear diff 2 wires. Let me know if you have a meter and I will walk you through the tests on both. Takes only about 20 minutes to test both. Get back to me.
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Wednesday, March 24th, 2021 AT 10:56 AM
Tiny
DUCATIMN
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  • 6 POSTS
My next move was going to be replacing the VSS, testing it before could save some money. Yes, I have a multi-meter.
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Wednesday, March 24th, 2021 AT 10:56 AM
Tiny
RACEFAN966
  • MECHANIC
  • 5,029 POSTS
Should measure between 190 to 250 ohms. I almost forgot we can check the transmission range sensor too. Let me know how it goes. Here is a pic of the VSS.


https://www.2carpros.com/forum/automotive_pictures/249564_551041_1.jpg

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Wednesday, March 24th, 2021 AT 10:56 AM
Tiny
DUCATIMN
  • MEMBER
  • 6 POSTS
Whien I tested the VSS resistance I received a reading of 1390 ohms. DId I test it correctly? I tested the two poles on the sensor where the plug goes in. I had zero if I tested the pole that inserts into diff to either plug pole. The pole on the plug that inserts into diff was flush with the plastic, where the picture you sent of the sensor pole extends out. Is that a clue that the sensor is bad or do I have a different sensor than pictured?

Update: It occurred more today, I was able to pay more attention this time. It seems more like when I press the throttle it is not reacting, maybe it isn't a shifting problem. It still does not seem to be running bad or rough, just like it isn't responding to the throttle (problem is intermittent). Maybe?
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Wednesday, March 24th, 2021 AT 10:56 AM
Tiny
RACEFAN966
  • MECHANIC
  • 5,029 POSTS
Ok if you got the ohms you got then the VSS is not good. You just unplug and ohm the terms on the VSS itself not the wire harness. Now as for the pic this is just a pic so you know what to look for. Yours is problably flush on the bottom. Get back to me and we will go from there.
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Wednesday, March 24th, 2021 AT 10:56 AM
Tiny
DUCATIMN
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That's how I tested it and that is the reading I received. I even went back and tried it a couple times thinking I was doing it wrong. My speedo does not act funny when problem is occurring, should it? I was starting to lean towrds the TPS because the speedo and odo were not acting up.

Thanks again for your help.
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Wednesday, March 24th, 2021 AT 10:56 AM
Tiny
RACEFAN966
  • MECHANIC
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Ok thats fine we can test that to make sure weather or not it is good. The speedo may not alway's act up. I must ask is the cruise control working? What size V8 do you have? If it is the 5.8 ltr then is it California emissions or not (this info will be on the underhood sticker). Here is the TPS test. So you first need to find the gray wire with the white stripe at the TPS plug in connector. Now you will need a paper clip, with the paper clip you will back probe the connector at that wire. Now hook up your meter and set it on 12 ot 20 volts (which ever option you have on your meter). Now turn the key on engine off. You should get a reading of.8 to 1 volt. Now slowly lift the throttle the voltage should steadily and gradually increase with no drops or glitches as you open the throttle. Now at wide open throttle you get 4.5 to 5 volts. Let me know what you find and please give the answers to the questions above too. Thanks.
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Wednesday, March 24th, 2021 AT 10:56 AM
Tiny
DUCATIMN
  • MEMBER
  • 6 POSTS
The cruise does work when the problem is occurring. I have a 5.0L engine. I finally gave up and brought it to a mechanic to scan the codes before I started replacing parts willy nilly. He couldn't retrieve any codes. Bu tsaid it was running lean at the top end and rich at the bottom end. He replaced the O2 sensor. Everything was working great for about 10 miles then the problem started again(problem has been continous just before bringing it in).
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Wednesday, March 24th, 2021 AT 10:56 AM
Tiny
RACEFAN966
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Ok so lets look back at some basics if you would. How old is the fuel filter? How old are the spark plugs and wires? How old is the distributor cap and rotor? Are willing to do a couple more test? I would like to check the coolant temp sensor and air charge temp sensor and then the map sensor. Get back to me and let me know what you would like to do.
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Wednesday, March 24th, 2021 AT 10:56 AM
Tiny
DUCATIMN
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Another update: Brought the truck back to the mechanic, he replaced the O2 sensor again and made sure to clean the oil out of the plug really well. He thinks leaking oil on the sensor caused everything and that he may not have cleaned the plug good enough the first time. He put in an O2 sensor with longer wires so he could tie it up out of the path of leaking oil. It had been running good for a week now, so hopefully that fixed it. (2nd trip to mechanic was free of charge)
I suppose I should try to find that oil leak and take care of it. I think it is just the oil pan gasket? It has become worse in the last couple months. Is this a simple fix or do you have to mess with motor mounts, just wondering if I can do it after work or should wait for the weekend?
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Wednesday, March 24th, 2021 AT 10:56 AM
Tiny
RACEFAN966
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Glad to hear it is running good. Now as for the oil leak it could be the oil pan gasket or the valve cover gaskets. If you need help with procedures just let me know once you found the leak. If it is the oil pan do your self the favor and buy the one piece gasket. They cost a bit more but you won't be doing it again anytime soon. Let me know what you find.
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Wednesday, March 24th, 2021 AT 10:56 AM

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