Bonneville America Forums Forums Technical Forums General Tech Engine Cutting Out - TPS Sensor Acting Up

This is more of an FYI for some of you who might be having similar problems.

Engine started cutting out while cruising around the city 2 days ago. Bike would run fine for about 15 minutes then just cut out on both cylinders for a second or two then run, then quit and run again. Did this several times then it would run fine. It almost felt like the engine was cutting out like it does when you hit the rev limiter. It only acted up when I was cruising at between 2000 and 3500 rpm. Engine idled ok and full throttle was ok. A couple of times it quit while accelerating from a stop. Parked the bike to think about the problem. Next day did the same thing. Cracked the tank vent, cycled the petcock to reserve and back, pulled the choke but it made no difference. Idled ok and full throttle was ok but the mid range was messing up after about 15 minutes of riding. I checked the forums and found a post some time ago about a person who had a problem with their throttle positon sensor. They had similar symptoms and they unplugged the sensor and everything ran fine. This got me thinking because I recently had a problem a couple of months ago with the sensor filling up with water. Anyway I checked all the electrics again, primary and secondary wires on coils ok, resistance ok, pickup coil at 564 ohms, ok. but the throttle position sensor was acting up. It has 3 wires and the resistance should change as the throttle is move from stop to stop. I had some erratic resistance readings in the mid range. I unplugged the sensor and took her for a ride. Everything ran fine. Went out for over an hour and it purred. Didn't notice any difference in performance but I did notice that there was virtually no more popping in decelleration. Anyway, the cutting out problem appears to be resolved because of a TPS sensor?????

Any of you fellows disconnect their TPS sensor? Did you notice any adverse effects with gas mileage, performance, driveability? I don't know if the sensor is replaceable??? One thing I have to emphasize is the tremendous reduction in decel popping. I purposely decelerated my bike from high speed to try to get it to pop and it didn't. Anyone up to trying?

That's a pretty interesting question and result. Not sure what the long term effects would be without the TPS. If you don't get an answer here, you might want to post in the Bonnie/T100 forum at NewBonnevilleRiders. The standard Bonnie folks seem to be more inclined to engine changes like that and might have your answer.
http://www.newbonnevilleriders.com/forum/forumdisplay.php?f=2

I disconnected mine because I was having trouble with my bike cutting out after hitting the rev limiter. The bike would lose power with no throttle response at all for about 10-15 seconds. After disconnecting the TPS wires she runs great and the rev limiter works as was intended. No adverse effects at all. I wouldn't worry about it and leave it disconnected if it is running OK now.

"Any of you fellows disconnect their TPS sensor? "
Not me but many have. Like when you change out the oem carbs for anything else...

"Did you notice any adverse effects with gas mileage, performance, driveability?"
n/a

"I don't know if the sensor is replaceable??? "
No. It is only available as an oem part WITH a complete set of $1700+ carbs.
Yes. if you buy a used one on fleabay.

I thought the thing was useless clutter and ditched it long time ago.
The end of the throttle shaft where it came off was colored green with dye chem or something.
I daubed a little "chrome" paint on that.
Also got rid of the resultant unused wiring.
No adverse effects that I can tell.

Hello,
I can report some similary experiance regardening the TPS.
Up untill spring -07 I used the standard CVK with the TPS and it was popping on de-acceleration. Then I switched to Keihin CRII (no TPS) and the popping disappeard. This summer I put the CVK back again for some other reasons and of course the popping was back. Up until now I thought that the popping was caused by the CVK in general, not the TPS in perticular. So this afternoon I disconnected the TPS on my CVK and went for a ride. Sure enough the popping was gone! Interesting. I will keep a cloose look to see if anything else changes also.
Regards
Hasse

Thx Hasse for confirming my findings.

I'd really be interested in the reference resistance readings you might have for the three wires from the TPS. One pair had a range from approx 1800 to approx 6000 ohms for idle to wide open and was linear. The 2nd pair had a steady setting or around 4500 ohms no matter what the throttle position. The third pair started at around 2750 for idle but jumped around in the mid throttle setting all over the map. Full throttle settled down around 4700 ohms. This is what I thought was causing my cutting out condition. Now I'm trying to figure out if the sensor is at fault of the CDI?

If you fellows who have swapped out your carbs to non TPS units have had no problems, what the heck is it there for?

Anyway, it's not going to be replaced for the price of a set of carbs.

Fellows, I can't reinforce this enough, there is no more popping on decel. Go figure. The TPS has to be affecting the timing somehow.

havent had tps for a long time and no issues at all. bike runs great

Frank

What are the correct settings?

I saved this tip when I first found it without saving the source:

Quote:

---

TPS readings from a
showroom bike are:

Blue & Yellow wires = 4.42K OHMS (4.40-4.44) closed throttle &
1.38K OHMS (1.36-1.40) wide open throttle.

Black & Yellow wires = 0.81k OHMS (0.79-0.83) closed throttle &
3.96k OHMS (3.94-3.98) wide open throttle.

---

Performance wise, running with and without the TPS hooked up showed no difference on the dyno. I ran it connected and then disconnected and the two power lines were almost identical. I can't say about the popping on decel, but there is no power increase one way or another.

how do you disconect it?
Now I want to try it out.

never pulled your carbs eh?

Are you refering to Mr.Lucas,aka"The prince of darkness",
maker of all those wonderful, snap,crackle,and pop electrics?

You know that's interesting... I was lamenting my problems with a guy that loaned me his phone to call the dealer to come pick up my dead bike from the side of the road a couple of weekends back. Out of nowhere he says "Know why Brits drink warm beer? Lucas makes refrigerators"

Good one

Looks like mine is already disconnected by the previous owner....ok.
Can’t imagine how bad it would pop with it connected..

Its the seal between the header and muffler.I sealed the right side last week and its a ton better,the left was never as bad but I am going to do that too.