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Discussion Starter #1 (Edited)
I have a 2002 f4i, about 20k miles on it. Only mod is MIcron exhaust. While I'm unsure if the previous owner abused it, I know I do not. I started to get the infamous CCT buzzing so I replaced the tensioner and the bike was running a little rough afterwards. After reinspection I notice I left a vacuum hose off the left side of my airbox. Put the bike back together and everything felt great for about 100 miles or so. Now the bike is slow to accelerate. No real hesitation or bog, just slow rpm climbing, also the FI light has come on since, It is flashing 8 times which I understand is the TP sensor. If I unplug mine with the bike running no change occurs. I would expect the idle to dip or raise since the computer isn't reading throttle position any longer. I am wrong to assume this?

Furthermore being that I am a college student funds are bit low, I am willing to buy a used set of throttle bodies online to replace the sensor, but is this geneally a bad idea?

Sorry for the long post but the last 6,000 miles this years has been nothing but a dream coming from a ninja 650r to the f4i. However, I am losing hope in winning this battle, because I honestly don't know if the TP sensor would cause my symptoms or if it is just coincidental. Thanks to all those who respond.
 

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*If* the TPS has failed completely, then the ECU would not get a signal from it and thus would not see a difference when you unplug it. You need to test the TPS to see if it is faulty or not. I would suggest ordering a service manual. Also, while Honda does not sell the TPS by itself the good news, the use the same TPS sensors on some of their cars. So this opens up a wealth of potential places to get a replacement. Some aftermarket companies also sell them; you might need to put the current connector on it. Before replacing it though, I would test the TPS sensor. If it checks out, then check the wiring as well. You have no idea what the PO has done. If there is a wiring issue, you can replace the entire TB assembly with a brand new one and still have an issue. If the wiring checks out and the TPS doesn't then find a suitable replacement or a used TB assembly.
 

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Discussion Starter #3
Based on the big IF is it unlikely for one to fail? I checked the harness connectors and all were good. I didn't pull the look and check the wires though.
 

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All you need is a voltmeter to check continuity from end to end. There should be a total of three wires. One is the ground, another should be the 5 volt power and the last would be the return to the ECU. Off the top of my head (i.e. I might be wrong) is that when the throttle is closed, the TPS should give .5 volts and at wide open it will provide 4.5 volts. In between closed and wide open will be between .5 and 4.5 volts. More throttle means more voltage reported.

It is not unlikely for one to fail. Honda just doesn't sell the TPS by itself and just sells the entire TB assembly as a complete unit. I have heard that the same TPS sensor is used on Honda cars. So if you can get access to the TPS, you can compare it and the connector to what is used on on Honda cars and find a compatible unit to use. That should be far cheaper than a complete TB assembly with the big advantage being that you have a new TPS sensor rather than a used one.

The big if is to make sure it is the TPS. It is fairly easy to check and the same holds true for the wiring. Some bikes also start to have ground issues as some of the ground wires start to fail where they all meet. Sometimes there is a ground plug (big green connector) and other models had all the grounds come into the wiring loom and then electrical tape was used to cover them. There was a large bump in the wiring loom where they did this. A faulty ground can cause weird readings from sensors.
 

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Here is a picture of a 2004 F4i TB assembly.


This looks like the same unit but this is an aftermarket one


So you could see if the local Honda dealer sells them. If you have alternate transportation, take the one off of the bike and take it to the dealer. I would call and make sure they have at least one TPS in stock though. They won't be able to look up what your F4i takes especially since Honda doesn't provide a part number.
 

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Discussion Starter #6
I guess I'll have no choice but to invest some time into it. The issue is the time, I go to school 70 miles from my house and normally use the bike as my transportation because of the great mileage. Thanks for the help, I'll get back to you with what I find. Do you just grind those weird heads off of the tps to remove? I found a used throttle body with fuel regulator, rails, tested tps, and injectors for 50 dollars. Maybe it's worth it? The only issue I see is mine is a Cali emission, the used set are regular.
 

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For the screws, use a Dremel and make the screws slotted so you can remove them.

I don't think the TB assembly is different from the CA to the 49-state variant.

$50 gives you some spare parts for the future. An aftermarket TPS is in the $20+ range.
 

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Discussion Starter #8
I just got through testing the sensor, the sensor is giving me the correct voltage without issue. Could it possible be when it gets hot it is faulty? Or it's faulty when it chooses to be?
 

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Discussion Starter #10
I checked it at the ecu and the voltage is the same in return. Strange thing is it was all fine for awhile. I got pissed took a break and rechecked now the voyage on return is 5 volts at idle and throttle makes no change. I think the sensor is intermittently failing.
 

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It very well could be the sensor. The ECU should never see 5 volts. So you either need to replace the TB assembly or just the sensor.
 

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Sometimes they can develop dead spots which is commonly what occurs. Seeing 5 volts going to the ECU should not been seen since the valid range is from .5 to 4.5 volts. Some computers know this and report a different error code if it is under .5 or over 4.5 volts. So when a TPS is faulty, it can obviously pass back more than 4.5 volts.

Unless someone else has another suggestion, I would go with replacing the TB assembly or the TPS and see what happens.
 

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Discussion Starter #14
Ok I just ordered a used tb with a tested tps. It was 50 dollars shipped. I'd prefer to use an oem tps rather than aftermarket. The way I tested the old tps will be how I install the new one correct? Just set the idle to .5 volts and check to make sure full throttle is 4.5
 

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Discussion Starter #16
Awesome I really appreciate your help. Bikes are rather new to me. I work on classic cars, Chevy 350 is easy to me. This little motor is a wonder to me. Over winter I'm going to strip it. Install new fairings and go over the whole harness because previous owner did a hack job installing lights. Doesn't help he dropped it either but for 2700 bucks I feel I got a deal.
 

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Discussion Starter #18
I installed a new one and it tested fine. I took it out and I'm having the same issue so I tested it again and it tested perfect. So I start the bike up to test and when the bike is running it seems unresponsive on the voltmeter. What could possibly be going on here.
 
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