1994 F-150 Engine Light Downshift
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1994 F-150 Engine Light Downshift
Hi all. I am an old noob here and have a problem with my 1994 F-150. It has a little over 76,000 miles, original. Well, recently the Check Engine came on and I noticed that it didn't want to downshift properly. If I come to a stop, it will drop down but if coming to a grade on the highway or around town, I press down on the gas pedal, no response. The truck willl lug down and not downshift. But I can manually pull the lever down to 2nd and it will downshift and I can then put the lever back to drive and the truck will normally upshift as necessary.
I think probably the TPS is out but before I spend $35 at AutoZone I want to make sure. Any ideas? I went there to get them to read the code but they can't read anything older than a '96.
I think probably the TPS is out but before I spend $35 at AutoZone I want to make sure. Any ideas? I went there to get them to read the code but they can't read anything older than a '96.
Fleet Owner
Joined: Oct 2005
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From: Kentucky
Bring the engine/transmission up to operating temperature then follow this procedure: Ford Fuel Injection How To Run a Self-Test
Or purchase an Equus 3145 Ford Digital Code Reader
Or purchase an Equus 3145 Ford Digital Code Reader
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All righty. I have several faults but I am going to tackle what I think is the one causing the others.
KOEO: ACT sensor signal less than 0.2 v.
TPS circuit below 0.6 v. This is where I'm starting.
CM: ACT sensor signal less than 0.2 v
EGR valve opening not detected
KOEO: ACT sensor signal less than 0.2 v.
TPS circuit below 0.6 v. This is where I'm starting.
CM: ACT sensor signal less than 0.2 v
EGR valve opening not detected
Fleet Owner
Joined: Oct 2005
Posts: 20,786
Likes: 1,751
From: Kentucky
The TPS is a common cause of idle and/or shifting problems. Before replacing it, measure the voltage with the throttle closed, then slowly open the throttle while watching the signal output. It should be a steady climb towards VREF, 5 VDC. If there are any dips or spikes it is bad.
I also take the closed voltage reading with a grain of salt. Always check to see if a PO has jacked around with the idle stop screw. If the throttle blade has been tweaked you may need to re-adjust it. In many cases when this happens the closed throttle voltage is too high, it is rare for it to be too low but it can happen.
The ACT problem can affect driveability as well as MPGs. Ryan has some great info here: Ford Fuel Injection Air Charge Temperature (ACT)
EGR opening not detected can be a vacuum supply issue such as broken vacuum tubes, EVR or a faulty feedback sensor (EVP).
I also take the closed voltage reading with a grain of salt. Always check to see if a PO has jacked around with the idle stop screw. If the throttle blade has been tweaked you may need to re-adjust it. In many cases when this happens the closed throttle voltage is too high, it is rare for it to be too low but it can happen.
The ACT problem can affect driveability as well as MPGs. Ryan has some great info here: Ford Fuel Injection Air Charge Temperature (ACT)
EGR opening not detected can be a vacuum supply issue such as broken vacuum tubes, EVR or a faulty feedback sensor (EVP).
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Thanks for some good info. The only problem with the truck is the downshifting when needed.If I come to a stop it will downshift on its own or if manually pull the shifter into second then it will drop down. I will check tomorrow. Thanks
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