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03' RC51 Erratic Idle

really need to measure output voltage of TPS and MAP to determine if they are proper. Vacuum leak will cause MAP to report higher-than-actual load and ECU injects too much petrol. Leading to stumbling and erratic idle.
 
DannoXYZ said:
really need to measure output voltage of TPS and MAP to determine if they are proper. Vacuum leak will cause MAP to report higher-than-actual load and ECU injects too much petrol. Leading to stumbling and erratic idle.
Click to expand...

Yeah, I was think you're on to it.

Hopefully I'll have time to test it today.

Cheers
 
Still trying to figure out tests. Especially on the TPS.

Messing with the RR here.

I sprayed carb cleaner around the hoses, and haven't found any leaks yet.

I see a mechanic in my near future :wtf
 

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I sent a vid to a local mechanic who knows Hondas. He 'thinks' it's the TPS but has never seen the weird idle before. TPS means changing the throttle bodies and that can't be cheap. :wtf

*Just tried testing the ohms on the TPS. The reading I saw was 4.28 but of course I have no idea if I did it right.
***Edit, the thing I tested between the throttle bodies was the MAP sensor, not the TPS

(not my pic, just showing the MAP sensor)
mapsensorlocation-jpg.14334
 
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Yesterday it started, & idled without revving up. Instead it backfired & stalled. More proof of a vacuum leak?

I didn't want to keep it running for too long in case I was doing any damage but it's weird that it stopped doing the 3000-3500 rpm revs.

New Vid: https://youtu.be/Y9tB7ot6xds

BTW: It looks like someone went to town on the ECU/CDI

Sorry for all the posts but I'm going nucking futs out here. It's been around 80 all week & I have track days coming up.
 

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weasel said:
Yesterday it started, & idled without revving up. Instead it backfired & stalled. More proof of a vacuum leak?

I didn't want to keep it running for too long in case I was doing any damage but it's weird that it stopped doing the 3000-3500 rpm revs.

New Vid: https://youtu.be/Y9tB7ot6xds

BTW: It looks like someone went to town on the ECU/CDI

Sorry for all the posts but I'm going nucking futs out here. It's been around 80 all week & I have track days coming up.
Click to expand...

What's all the dirt and grime on the electronic circuit board? No, its not guaranteed to malfunction, but its definitely not supposed to be that way. If you get humidity inside it will behave unpredictably.
 
Right? It surprised the crap outta me. I'm gonna clean it up. I'm guessing that's a sign that the ECU's been flashed(?)

Tom G said:
What's all the dirt and grime on the electronic circuit board? No, its not guaranteed to malfunction, but its definitely not supposed to be that way. If you get humidity inside it will behave unpredictably.
Click to expand...
 
Popping and backfire could be sign of leak. Lean mixtures from leak may cause misfires and accumulation of unburnt petrol. Which then does giant >BOOM< in your muffler.

Improper adjustments to ECU maps would certainly cause issues. Try to find shop with proper flashing software and have them download maps and compare to stock map. If there's difference, that might be issue. Then flash with stock maps and see how it runs. Or swap with known-good ECU from well-running bike.
 
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Why the hell would someone cut the ecu open, when you just plug into it to reflash?!?!

I think that ecu may be fubar.
 
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Nobody ever flashed RC51 ecus. They were all PC.

Disconnect the PC, get yourself a known good stock ECU and hopefully everything clears up. I dunno what happened to that ECU but someone should be on the sex offender registry for molesting that thing.
 
Yeah, looks some of driver transistors were replaced. And heatsink modified or replaced.
 
scootergmc said:
Nobody ever flashed RC51 ecus. They were all PC.

Disconnect the PC, get yourself a known good stock ECU and hopefully everything clears up. I dunno what happened to that ECU but someone should be on the sex offender registry for molesting that thing.
Click to expand...

:rofl

Thanks all.

Guess it's off to a mechanic next week.
 
If you're experiencing a *continuous* high idle then suspect an air leak because
on a fuel injection system any air that gets past the throttle bodies the map just
adds the corresponding fuel... the result is high uncontrolled idle... the fact that
your problem is not continuous suggest something else... I'd view the engine
running with the lid of the airbox removed so you can note if the throttle
butterflies move or not during your intermittent high idle...
 
Now I just need to figure out how to remove the airbox lid. :)

Tanks,

Busy Little Shop said:
I'd view the engine
running with the lid of the airbox removed so you can note if the throttle
butterflies move or not during your intermittent high idle...
Click to expand...
 
That’s not the ecu. That’s the CDI box. Supply’s voltage to ignition coils. When they fail sometimes people open them and do a repair that Rc51forums posted. The ecu is in front of the CDI and next to the battery. By the 12.64 volts is not fully charged. 12.8 or above for lead cell type & 13.2 for lithium.
 
Airbox lid just has self tapping screws around the perimeter of the top. Easy peasey.
 
stever said:
That’s not the ecu. That’s the CDI box. Supply’s voltage to ignition coils. When they fail sometimes people open them and do a repair that Rc51forums posted. The ecu is in front of the CDI and next to the battery. By the 12.64 volts is not fully charged. 12.8 or above for lead cell type & 13.2 for lithium.
Click to expand...

If it's a used battery, 12.64 volts is completely charged, is considered a full charge, and is still in the good range. You will only see 12.8 with a brand new battery.
 
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stever said:
Airbox lid just has self tapping screws around the perimeter of the top. Easy peasey.
Click to expand...

Yeah, no. I need to remove all the hoses and the throttle bodies just to get the airbox lid off.

Thanks peoples. It's off the the mechanic on Friday.
 

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Well, that's not really the airbox "lid" down there, more like the base.
And that is a tasty aftermarket CF one at that....which may have different mounting/attachment as the stock one, where the lid does come off with a few captive phillips screws.
 
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