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Discussion Starter · #1 ·
Just wondering what the TPS idle voltage spec should be for a destroyer. Is it the same as the street bikes, .45? I began digging into this do to the hard start/ eratic idle problem that i have had with this bike since I took it off the showroom floor. Tonight I have found that my initial idle voltage was at 1.1V. After making some adjustments I could only get it down to .85V. The throttle plates are to the point where they are sticking to the bores. I can not go any farther. I removed the TPS from the throttle body and left it plugged into the harness to take a reading. Got .55v. Got it to go down to .38v with a little assistance from a screw driver. The tps feels as if there is a spring in it and I am starting to wonder if it is stretched. Regardless something doesnt seem right if .45v is the correct spec. Any help or thoughts would be greatly appreciated.
 

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Noel
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Closing up the TB to near closed should not be done, the Destroyer TB is intentionally set to pass more IDLE air past the blades to get you into the ~2000 RPM Idle Speed~ this higher idle is for cam/valve train dynamics.

The folks I've talked to & I 've tried it myself, is to remove the TPS, elongate the two mounting tab holes enough to allow you to turn it down to the neighborhood of that ~0.45v range. you need to ditch the brass ferules to get the openings wide enough.

Theory is that when you go WOT, the sweep of the TPS shows a measureable span to WIDE OPEN, this delta in resistance is used by the ECM/MAP to know that you truly want "FULL POWER"

One caveat, the TPS tabs are more susceptible to breaking, have spares on hand if this happens.
 

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Discussion Starter · #3 ·
Other post on this forum have stated that the IAC motor will not operate unless the throttle is less than 1%. This is what made me wonder about the idle voltage. I now understand that this cannot be true with the destroyer. I've thought about elongating the holes on the TPS but it seems like I would be chasing my tail. A lower adjustment would take away from the top, a higher adjustment would take away from the lower. I removed the Tps from the throttlebody and left it plugged in. I then attempted to start the engine and achieved the same result. Hard start. I no longer believe that the tps is the problem. My next thought is to inspect the throttle cables and throttlebody linkage. Something is not in sync because the engine will run on one cylinder when first started.
 

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Noel
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I understand partly what your saying about chasing your tail, you would be seeing the IAC trying to self correct the idle conditions, you might even toss a code as a street map with a more sedate idle RPM would cause the ECM to think that it's not able to ~control~ the high idle.

Now consider the degrees of movement of the TPS and it's measurable range for instance 0'dgr to' 90'dgr.

Then the throttle plate shaft 5'degr to 90'dgr (this is an example not the real values, since the throttle on a DESTROYER) is open much more that than the street setup you can ensure the sweep is centered within the measurable range of the TPS.

In turn informing the ECM/MAP that maximum fuel is called for as your running the 1/8 or 1/4 mile.

All a matter of which end of the spectrum is most important, smooth off idle control or guaranteed maximum power at the WOT.
 

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I would be inclined to think that there is other issue(s) here.
Being that be bike sat for so long unfired.
Chances are that a set of valve springs were compressed for all this time and most likely lost there spring pressure and there ability to hold valve closed correctly or pull it closed fast as needed with the aggressive cam profiles. This would make for hard starts and problems idling IMO. May run fairly well low and mid RPM but may suffer valve float in upper RPMs depends on what valves have weaker springs.
I would think the ECM program for the destroyer would be compensated for the greater TB blade opening and as long as you have at least 4.5 volts at WOT ECM will see 100% TPS.

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Discussion Starter · #7 ·
Just an update... I checked the cables and linkage over the weekend and all seems ok. I decided to purchase a vacuum sync gauge just for reassurance. Should be here by the end of the week.

I removed the tps once again and left it plugged in. Checked voltage to make sure it was around . 5v. Hit the start button and walla, she fired up and purred like a kitten for about 15 seconds and then the idle shot up to 2900. I burped the throttle and it came back down to 2000 for a few seconds and then shot back up. Iac steps set too high? I know I reset it to factory spec. :mad:
 

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Discussion Starter · #8 ·
So tonight My twinmax carb sync tool finally arrived at my doorstep. I rigged up some fittings that will screw into the intake throat of each head where the existing screws already exist.

Upon warming up the bike I encountered the same old thing, start,stall,stArt, stall. I even modified the tps to allow for a lower voltage at idle. .61v and 0 percent according to the rt data mode. I have also been fussing with iac steps and warmup enrichment for the past several days.

Once I finally got it running and idling I went to burp the throttle and the rpm's went up, came down, and then magically went back up and stayed up to about 3000. Tried to twist the throttle to get the rpm's to come back down, but no such luck. The throttle linkage was at full rest. It has to be the iac motor.

All of the described above has been a constant problem since day one. Tommorow I plan on going to a remote area for the tb sync to avoid pissing off the neighbors anymore. The question of the day is, what would cause the iac to suddenly allow more air into the intake while the engine is at operating temp. Keep in mind that the engine was idling fine until I burped the throttle.
 

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Noel
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Consider all the things that often go wrong on Destroyers: all these factors, if questionable, should be addressed:
  • Fouled plugs,
  • Gummed injectors (U4 fuel is not friendly)
  • Unplugged or damaged sensors.
  • Weak battery, poor performing charging system, racing conditions do not allow proper recharging.
  • Stalling during initial start sequence.
  • Failure to allow proper ~REBOOT~ of the ECM after a stall.
  • Leading to erratic ECM operation and action of critical components.
 

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Discussion Starter · #11 ·
I'm glad I'm not the only one. I have never owned a v-rod before this nor have I had the pleasure to be around many destroyers, except for one other. The guy bought his from another local dealer a couple years back. One of the track owners brought it to my attention and hooked me up with guy. We try to get together every now and then. He brought his destroyer out last year and I watched him start it. He just hit the button and walked away. The engine sounded flawless. Then he came over and watched me start mine. It was embarrassing for me. I asked him what fuel he was running, to which he replied regular old 110. He had the bike dynoed right after he bought it. Said he never had a problem. That made me wonder if the u4.4 is causing my problem. I hope to learn in the near future.
 

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Discussion Starter · #13 ·
The start stall problem only exists when the engine is cold. It will run for 5 to 10 seconds then stall, unless I burp the throttle, which I hate doing to a cold engine. I guess a map sensor is worth a shot.
 

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Since it runs longer (5-10 sec) I'm thinking water temp sensor. It may be telling ECM its cold enough at first to call for enrichment when with just a little heat sensor goes high and ECM leans mix out to normal AFR for idle.

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Discussion Starter · #15 ·
Update... Ordered a new map sensor. I compared resisitance readings between old and new. They weren't even close. Installed the new one and she fired right up and idled like a champ. Have started the engine on several occasions over the past few weeks and have had no issues. I believe the issue has finally been solved. Thanks to everyone for your input.
 

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Noel
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Update... Ordered a new map sensor. I compared resisitance readings between old and new. They weren't even close. Installed the new one and she fired right up and idled like a champ. Have started the engine on several occasions over the past few weeks and have had no issues. I believe the issue has finally been solved. Thanks to everyone for your input.
Good to hear, yes that u4 does seem to eat MAPS, hoping for smooth running season for you!!
 

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Do not know if you have the SERT, but benchmark your values and it would help ID issues in the future. My MAP sensor crapped out and the tuning software allowed me to identify the failed component.
 

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Noel
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start and then stall after 1 second could be a map sensor Problem, typical symptom

Going to look into this myself, MAP was last changed on 2016 refresh build, the Destroyer is doing what Clints describing. I am also going to look at TPS issues, especially if one of the ears broke and it's not maintaining proper position.
 

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Noel
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Since it runs longer (5-10 sec) I'm thinking water temp sensor. It may be telling ECM its cold enough at first to call for enrichment when with just a little heat sensor goes high and ECM leans mix out to normal AFR for idle.

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AHHHHHH, this is another issue I am experiencing, I use Franks fan bypass switch, seems that it should be returned to NORMAL mode after finishing a cool down cycle, the next cold/lukewarm starts have not been happening reliably if it's in the FAN on mode or FAN off mode.
 

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Clint, are you running the temperature bypass switch that sets the engine temperature to 185 degrees Fahrenheit?
If I leave the switch on at start the bike labors to start, then if I turn off the switch the bike starts immediately.
 
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