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Throttle Position Sensor, Help?

5K views 22 replies 4 participants last post by  Riggerwings 
#1 ·
So my truck has a few issues that I've mentioned in other threads and everything points to the TPS. I purchased a new one on RockAuto and when I installed it, the truck would start and immediately die. I figured maybe I bought the wrong sensor so I sent it back. Fast forward about 2 weeks and I ordered another from Ebay (brand new in the box). I installed it tonight and it did the exact same thing.

I did disconnect the negative cable and I even "reset" the codes by holding the key in the start position for 15 seconds with the battery disconnected. When I test for codes, I get the "P done" code, which means everything is good.

Why then, will my truck not work with a new throttle position sensor. This has been with 2 brand new TPS's! I reinstalled the old one, tested for codes and "P done" again. It fired right up.

Why can't I make a new TPS work... is there a trick to it that I don't know? Help!
 
#2 ·
Couple suggestions I can think of, get a new IAC valve, and check the base voltage ( throttle plate closed ) thru the TPS. Using a multimeter on DC voltage, place the positive lead and back probe the middle wire in the TPS sensor connector. Place the black lead on any earth ground ( or on the negative batt cable ). Turn the key to ON but don't start. You should have between .5-.75 VDC. With the throttle floored, it also shouldn't exceed 4.5VDC. Are you using mopar oem brand sensors?
 
#3 · (Edited)
Thanks for the response Blakota. I posted in another thread that I did exactly what you mentioned. With the throttle body at idle position, I was getting .588 volts (DC), at wide open throttle I was getting 3.817 volts. This is within good numbers right?

I installed 2 new TPS's so far and both do the same thing with making the truck die. I had to install the stock one again, which as far as I know is a Mopar.

I ordered a Mopar replacement last night so hopefully that solves the problems. Im not sure that the aftermarket TPS's are "calibrated" for my Dakota, seeing as they're good for numerous vehicles.

Hopefully that solves my issues, if not I may have to take it to Dodge to diagnose and fix. Who knows, maybe someone installed a tuner before and it's tuned specifically for something.

I'm at a loss if the Mopar TPS doesn't work.

EDIT: I also have an IAC on order. Could that be my issue all along with the TPS?
 
#4 ·
Not a problem man. .58 at idle position and 3.8 at WOT is right on the money. It's within range. It very well could be the IAC, usually when that's a problem the engine will refuse to run unless your foots on the gas! When you do replace the IAC, get a can of throttle body cleaner and clean out the TB real well. Clean where the IAC goes. Some guys take the throttle body all the way off, but I've never felt the need to do it.

At this point I'd say your issue is not with the TPS at all. I'd put my money on the IAC. From what I hear, TPS problems usually will make the engine surge, make the trans shift odd or drop out of overdrive. I had 1 go bad on me and the engine would idle at 1000 rpm sometimes. If I tapped the gas it would settle back down to 750.
 
#5 ·
Wow, the more I read I read the more I learn! Most of those symptoms you're describing are my issues. It usually only surges when I first put it into drive or reverse. Next, with the cruise control on it seems to have a shudder. As if the torque converter can figure out what to do.

Luckily, I ordered an IAC as well. I bought the truck on December 30th, but in January I did spray some TB cleaner into the TB. Maybe I will remove it to install the IAC, just to make sure everything is clean. But then again, I don't want to mess with something that doesn't need to be messed with.

I guess if the IAC fixes it, I'll go ahead and keep the Mopar TPS and install it.

I have the maintenance manual (digitally) but it's so hard to find things since its like 1300 pages. I wasn't sure if my TPS voltages were good or not, so thanks for confirming that. You give me hope for my IAC fixing my issues!
 
#6 ·
And you said you don't have a check engine light on? I've had IAC failures that never tripped a code! Sometimes when they're going bad, the rpm will drop like it wants to stall, then catch itself and come back, if you put the trans in gear. That's bc the plunger gets old, sticks and doesn't let air in quick enough to compensate for the increased load on the engine to stay running
 
#7 ·
Glad I can be of some assistance! Always glad to share whatever I may know if it can help someone.
 
#8 ·
Honestly, that was why I joined this forum, for the knowledge of others. I'm a ford guy and always have been. I have a pretty nicely modded 2008 Mustang GT that I bought new, and many of the things I've done to it I got help with from people on forums.

I only threw a code when I installed the new TPS, it was P0123, which I'm pretty sure is for TPS. At first the truck would start and immediately stall. Once I finally got it to run, even without putting it in gear, the truck would finally find idle then slowly go down in RPMs until it died.

The more you mention the IAC, the more it make sense to me. But why would a bad IAC cause a new TPS not to work? Maybe once I change them together they'll work together.
 
#9 ·
A faulty TPS will cause the IAC to not work properly. The PCM "learns" this and will change the way it operates the IAC based on TPS signal. Since you said you had a bad TPS and replaced it, now the truck neeeds to re-learn the IAC position. Which is why it dies imediatly after starting. The IAC isn't set correctly. Try starting it and holding gas pedal down some. If it will stay running pushing on gas pedal, then take it for a drive giving the PCM time to relearn. ALso cleaning the TB can help as well if the bottom of TB blades are gunked up not allowing air past them at idle. They aren't supposed to be sealed tight t idle.
 
#10 ·
So the IAC came in the mail today and I replaced it. The old one was pretty grimey and nasty. I also put one of the new TPS's on there and it started without dying but the idle was as if I was feathering the throttle a bit. It was up and down constantly. I threw the original TPS back on and it idled fine.

Yes, I did disconnect the negative terminal each time I swapped something. Once the TPS was back to original and with the new IAC in, I went for a test drive. The initial "surge" of the throttle is still there when going from park to reverse. I only drove about 4 miles total but I used the cruise control and it seems the shudder is gone. I'll have to test it again on the way to work tomorrow. So as it seems, one problem down. Hopefully I can install the Mopar TPS I bought and not have any issues.

If my stock TPS is still good (based on voltage) then why wont the other new ones work correctly? There's no codes to have to reset. How does it take to "learn" a new sensor? It's just adding up why one good TPS works and one doesn't.
 
#11 ·
I'd think after driving around for 40-50 it'd learn enough to not run rough. Whats odd is by disconnecting the battery it should start fresh, and shouldn't remember compensating for old sensors. But, what u could try too is turning the key to START, holding for 15-20 sec, with the negative cable disconnected. That truly resets the computer.
 
#15 ·
i got a 02 durango with the 4.7L, just out of curriosity, what is the correct idel RPM for this engine? Currently my idle flucuates from about 550-800 give or take. no hunting or surging, just at differnt times it idles at higher or lower RPM's no matter whether its a cold start or already nice and toasty from driving. I know my IACV is probably gummed up and dirty but I just havn't had the opportunity to clean it. that and the fact thats its the middle of winter in Canada, freezing cold with snow/rain/freezing rain conditions most every day and with no garage to work in, it dont make working on the rig fun. that coupled with the fact of getting that shit down inside the throttle body is never good for the engine lol!!
 
#18 ·
Well, the shudder is back and it seems even worse now. Again, it's only with the cruise control on. I can watch the RPMs change almost every time it happens now. Before I changed the IAC valve it wasnt this bad. My Mopar TPS hasn't come in yet but I don't have much faith in it since two other new TPS's didn't work. I'm losing faith in Dodge but I have too much money in it to sell it!
 
#19 ·
So I found a TSB for something that seems like the issue. It's TSB # 0803500

Description: SOME VEHICLES MAY EXHIBIT A SURGE WHILE THE SPEED CONTROL IS ENGAGED AT 74 - 76 KM/H (46 - 47 MPH) AND / OR AT 109 - 111 KM/H (68 - 69 MPH). *TT

Problem is, mine does it even at 55 mph so the speed range is a little off. I have to see if there was a re-flash or anything involved with it.

If so, will Dodge reflash it for free under the TSB, or will they still charge me $932874981327089 to do it?
 
#21 ·
Thanks HSKR, I figured as much haha.

New Update: I drove about 130 miles to my Dad's this weekend and the transmission was always shuddering on the highway. With or without cruise control on. I got there and thought it could be a transmission speed sensor, so I bought one and replaced it. On the drive back home I still had the same issues. It was worse though. Even doing 75mph it would randomly down shift on flat open road. I was pissed, thinking I needed a new transmission. Once I got home, I saw that my Mopar TPS came in over the weekend. I installed it this morning before work and the truck actually started. With the cheap TPS's the truck would always die. On the drive to work I didn't notice any shudder at all, or on the drive home. So far so good. I'm going to try to do a highway trip tonight and see how it goes.

Bottom line up front...Don't ever buy a cheap TPS. You can get them on Ebay for like $12 and the real Mopar part is like $65. I'm not sure why two cheap ones didn't work (both different brands). Don't be a cheap ass and buy the right part, otherwise you'll continue to have issues! This may not have solved my overall issue (though I hope it did) but the Mopar TPS worked from the start, unlike the aftermarket cheap stuff.
 
#22 ·
Glad to see it seems you got your troubles straight!! I bought a value craft in a pinch and 6 months later is when I had 1000rpm idle sometimes. It's possible the same Chinese company made both sensors u got! That's what they do.
 
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