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Discussion Starter · #1 ·
I have a 2007 VRSCDX (V&H 2 into 1, high air flow topless) that has a hard time staying running at Idle. While it's not as prominent when the engine is first started, eventually the idle will start to bounce from 950 to 1350RPM. I'd say 1 in 5 stoplights the RPMs will bounce so low that the engine will stall.

I'm showing no codes on the bike.

I have replaced the IAC, physically removed and cleaned the fuel injectors (although that doesn't rule them out), inspected and cleaned the rubber boots on the intake, as well as clean the throttle body that contacts the rubber boots very well with a wire brush.

I've checked the resistance of the TPS as well as monitored on my SEPST. The voltage and throttle position graphed out appears to have no glitches, goes from 0 to 100% smoothly.

In February, I had the bike tuned at my local dealership. After that, the low end seemed kind of chuggish. It's a bit harder to ride in 1st gear doing < 10. Not to say this is related to the problem, I'm just trying to give the whole recent history.

For the past month, the bike has had this idle swing, but it's now starting to stall at idle.

I have removed and cleaned the MAP sensor. I haven't completely ruled out MAP sensor, but I need to get a vacuum meter to properly check it.

I have a SEPST, so I have access to running graphs that show the problem. See attached images: idle_warm.jpg, throttle_blip.jpg, engine_start.jpg. In the idle_warm.jpg, the throttle bounces from 1432 to 967RPM. Again, this still happens on cold start, but it is not as pronounced.

The bike is a monster and runs good otherwise in the mid to high rpm range. This tune is yielding me 119HP, but I'm considering going back to stock tune to help rule out any issues that the tune may be causing (is that logical?)

I need help.
 

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Discussion Starter · #2 ·
Just a little further information on this: I went back and opened one of my old recorded runs from the SEPST and noticed that the MAP sensor regularly read 6-8in Hg at idle and now jumps around from 8-11in Hg.

This tells me either:
1. Map sensor is bad?
2. Map sensor is not bad and is just responding to changes in engine RPMs, but a swing of 3in Hg is a lot for a 400 rpm swing.
3. There is an intake leak? I've really gone over the intake with a fine tooth comb (and propane, starter fluid, and carb cleaner) without finding any leaks. Not to mention the MAP sensor appears to be located AFTER the intake boots and fuel injectors so I have a tendancy to believe it would accurately respond to leaks and not be so jumpy. Additionally, if there was a leak, I don't believe the MAP sensor would be up and down, I believe it would just give a constantly higher reading than normal.

Anyone second those thoughts?
 

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" In February, I had the bike tuned at my local dealership. After that, the low end seemed kind of chuggish. It's a bit harder to ride in 1st gear doing < 10. Not to say this is related to the problem, I'm just trying to give the whole recent history."

That sounds a bit suspect. Sounds like it's got worse. Have the dealer preferably as they tuned it or a local bike dyno run it with a sniffer and see what your F/A mixture is doing at idle and low speeds I wouldn't change the tune till you do that - let all here know, it's interesting and good luck !
 

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Based on the data, the MAP sensor is bad. It should be reading between low 20s to 30kpa at idle and 98-100 bike not running. A good sensor cannot be dragged down lower then 10.3 on hard decels. An intake leak would show higher then normal KPA. Fueling for the vrod is TPS based but timing is controlled with the MAP.
The TPS volts are a tad high as well. Should be .045-.047

Ron
 

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download the software mytune from www.tunemyharley.com and data log with the tuner..it will generate new VE tables and synchronize the cylinders..I think you have a bad tune,sometimes v rod's do this with just the canned map from HD..it's lean surging

you can try to set the Cylinder size 0.3 higher and see what happens,it will set the entire map richer..if the surging goes away,you know your map is lean
 

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Discussion Starter · #7 ·
Thanks, Ron. Eight inches Hg (mercury) is equivalent to 27KPA at idle, and my MAP load is 29.7in Hg while bike is not running (which is equivalent to 100.58 KPA. I believe this is in normal range.

I'm not totally ruling out the MAP sensor, but I hate to just start throwing money at parts until they're proven to be bad. I have a vacuum tester coming in the mail tonight so I can check the calibration of the MAP sensor to make sure it's operating without fluctuation and on a linear scale.

In regards to the TPS, we're essentially dealing with a potentiometer, so I'm not concerned with a 40 millivolt difference. The computer still reads this as 0% throttle and my service manual indicates a hot idle voltage of between .2 and .8 volts, so I'm well within spec.
 

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Discussion Starter · #8 ·
Thunderdemon, thanks for the advice. I have previously looked into tunemyharley but it only works with bikes that have o2 sensors.

I took the bike to the dealership yesterday afternoon and they are going to throw it back on the dyno at no cost under labor warranty, despite me being ~10 days past the labor warranty on the tuning. I figured it wouldn't hurt to have them re-evaluate it.

I can confirm that they used a sniffer to determine the AFR when it was on the Dyno previously, as the data in the file they gave me on the USB had 2 sets of data for AFR1 & AFR2 (assuming they took independent readings from each cylinder)
 

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Thanks, Ron. Eight inches Hg (mercury) is equivalent to 27KPA at idle, and my MAP load is 29.7in Hg while bike is not running (which is equivalent to 100.58 KPA. I believe this is in normal range.

I'm not totally ruling out the MAP sensor, but I hate to just start throwing money at parts until they're proven to be bad. I have a vacuum tester coming in the mail tonight so I can check the calibration of the MAP sensor to make sure it's operating without fluctuation and on a linear scale.

In regards to the TPS, we're essentially dealing with a potentiometer, so I'm not concerned with a 40 millivolt difference. The computer still reads this as 0% throttle and my service manual indicates a hot idle voltage of between .2 and .8 volts, so I'm well within spec.
Correct. I missed noting it was set to hg rather then the normal kpa standard. As for the tps spec, yes it's in range technically. The tps is set to 0 on each start but if the volts are too high there comes a point where the ECM will not see the engine as being at idle and the IAC will not set correctly. Not sure at what point it is but don't think 0.51 will cause that.
MAP for the vrod is responsible for timing. If it changes or bounces around it can be pulling higher and lower timing or hunting which in turn moves the idle rpm up and down, sometimes a lot. Set front and real cyl timing and closed throttle from 1200-1500 should all be set to the same value. 10kpa left and right of your normal idle kpa should also be the same value. If your hg has changed from your previous logs where it pulls timing will also change. Try logging the timing behavior and see if this is happening. Like you, without further testing, I can't explain why the hg would have changed beyond normal every day baro differences, which are small.
Ron
 

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Thunderdemon, thanks for the advice. I have previously looked into tunemyharley but it only works with bikes that have o2 sensors.

I took the bike to the dealership yesterday afternoon and they are going to throw it back on the dyno at no cost under labor warranty, despite me being ~10 days past the labor warranty on the tuning. I figured it wouldn't hurt to have them re-evaluate it.

I can confirm that they used a sniffer to determine the AFR when it was on the Dyno previously, as the data in the file they gave me on the USB had 2 sets of data for AFR1 & AFR2 (assuming they took independent readings from each cylinder)
sorry for the late response but mytune works great without O2 sensors also,I tune a lot af different bikes with it..glad your bike is good now
 

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Well that's great it's fixed, thanks for the follow up ! Kinda figured the dealer dyno tune had something to do with it. Based on the other thread like this currently here on the site with Mike & Ron talking the dealer may have neglected to properly adjust the warmup and low end mixture properly after they got the base map done ? I guess that can happen. My bike was the other end, it wouldn't run without stumbling bad above 6000 RPM, it felt like it was dropping a cylinder before I bought it. Working with the seller (that never revved it that high) we found out he had an open pipe removed when he bought it then reinstalled the stock pipe with hollow points but never retuned it. It was running so rich we had to lean it way out then she ran like a champ. Since then I've learned the sound & feel of rich and lean playing around with the simple Dobeck controller. Looking fwd. to a wide band O2 sensor Daytona TT system to really dial it in, not looking fwd. to the learning curve but I'm sure it's worth it. :blahblah: :D
 
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