I have hunted but not found the thottle position sensor output values. I have checked mine with a volt meter and am getting (if i follow the haynes) 5 volts on the signal line at idle which reduces to 1 volts at full throttle. The reference works the opposite. I kind of wonder if the connector is opposite what is in the haynes manual but the one thing I don't understand is why the reference is floating with throttle position.

The rest of the story is that I have a p1121 TSP to MAF mismatch reading. The MAF was changed about 6 months ago with a new from NAPA. I have a scanner that will display ODB sensors values real time and both the MAF and the thottle position seam to be reading and those values change as I drive in the maner I would expect. I'm not sure what to do next so any suggestions would be helpful.

Thanks,
jtdwab
P.S. 98 F150, 4.6L with 199,000 miles

 

Drill out the brass bushings - Tip it forward until you hit .99 or little lower in the key on position. -Then Reboot

Or , clean your MAF sensor.

 

First, thanks for the fast replay, second, what is the "brass bushing". I did clean my MAF about 2 days ago.

Thanks,
jtdwab

 

Hang on , I'll search for the thread.

 

https://www.f150online.com/forums/sh...ght=TPS+SENSOR

 

Thanks for the link that brings up a worse problem though which is why I was testing. I was going to replace mine due to the codes and that the MAF was new but I stripped out the head of the top phillips screw so I was trying to determine if I need to drill it out or leave it be. I will check the wires again I think I am at 1 volt though instead of .99.

 

Impact or vise grips - The Throttle body comes off in about 3 minutes . You can stick the screw head in a vise and turn just a little to break loose - be careful tho. You'll see what you have to do once you get to that point.

Replace with bolt heads .

 

I was getting a picture while you were posting but I don't have a sight to upload it to for a link.

I may try that. I allso was think of cutting the heads off with a dremel and then twisting the screws out. Its going to be a pain no matter what I do.

On the side I did notice that when at idle the scanner shows a constant 20% throttle and increases from there although it does stop at 93%-98%. I will do the removal tomorrow.

 

That is a perfectly normal observation of the TPS Load %

 

Okay so if 20% is normal for idle, then why does my truck bellow black smoke and run awful. It did have codes for Rich on both banks before this and I changed the fuel pressure regulator (I believe vacum is good and I don't have a gage for fuel pressure). After that the engine runs worse because it would only do this every so often before.

Something is bad wrong and I don't know where to go now. Thanks for any help.

 

On the 4.2l V6 it is between 14-20% on idle.

 

So if i assume the TPS is good does anybody know what the normal MAF readings should be in lb/min so I can check those values.

Thanks,
jtdwab

 

I would not make that assumption yet based on your initial post. The reference must remain constant at 5 V. I must suspect an error in your method of measuring it, perhaps due to a misidentification of the connector wires or a mis-placement of your negative test lead.

C123 (TPS) wires are as follows:

BR/W - Sig Rtn (ground/return)
GY/R - +5 V Ref
GY/W - Signal out

I also suspect you need the real Ford docs instead of the Haynes (which, IMHO, should be reserved strictly for when one runs out of Charmin).

From the 98 PCED for the 4.6 F150 w/auto

Hot idle - 4-5.1 grams/sec
2500 RPM - 11.5 - 15 grams/sec

As DC voltages:

Hot idle - .6 -.9
30 mph - .9 - 1.5
55 mph - 1.2 - 2.3


Simple answer - because it is being mis-fueled (overly rich). The question then becomes - why?

I'd suggest starting with the diagnostic for your retrieved fault code. Download it here: http://www.mediafire.com/?cu6dd6dxlnm

Entry point for your specific fault code is step DH15.

Of course, you'll have to get by that little mechanical difficulty with the screw first....

Steve

 

Remember if you take the TPS off you have to install it with the connectors facing down towards the engine then rotate UP to the front of the truck, this engages the splines inside and mates correctly to the throttle blade.

You may have to remove the throttle body to re-install, i had to, too close to put it on correctly. If you put it on incorrectly you'll get a TPS fault code because the blade and sensor are not connected.

 

Well after going ahead and pulling the TPS and then drilling it per jbrew as well as going through the diag provided by projectsho89 (thanks for that) I think the MAF is bad. I am reading 2-3 lb/min or 15gram/sec on a hot idle from the MAF so it looks like my newer sensor is bad.

I pulled it and the truck started to run much better so here is my next question. Can I leave it out and drive the truck? Its sunday and I want to return it to NAPA because it should be under warrenty so I have to do that tomorrow. Will it hurt to drive it say 20 miles tomorrow till I can get if fixed?

Thanks everybody for the help,
jtdwab