CBF1000

CBF1000 => General Maintenance, Servicing, and Mechanical => Topic started by: Marudny on 02 May, 2016, 07:43:53 PM

Title: Vacuum value at idle (rough idle problem).
Post by: Marudny on 02 May, 2016, 07:43:53 PM
Hi,
I have problem with my CBF 1000 FA (2012, 25kkm).
Problem look typical - rough idle and high fuel consumption (avg 9.0 liters per 100 km).

I've checked:
- vacuum lines - no leaks.
- oxygen sensor (brand new)
- spark plugs - clear.
- valves
- compression (12.5 bar on four cylinders)
- TPS - work good (resistance and voltage equals service manual values)
- throttle body with engine connections - no leaks

Last thing is throttle synchronization. Yes, i know that service manual says "don't do that", but after vacuum meter connected I found 4 different values . 710 mbar, 850 mbar (on that cylinder where leaks under the regulation screw), 740 mbar, 750 mbar. I did it with procedure: unplug MAP sensor, unplug IACV, remove vacuum lines (3 to map sensor, 1 to idc) and set vacuum values to 775 mbar (which gives 1080 rpm without IACV correction). I don't know if it correct value. When set to 800mbar rpms were 1100 rpm, engine was running stable but had problem with going down with rpm after rev (was very lazy - looked like IACV was opened at value and ECU closed it to maintain idle speed).

Here is a rpm meter movie:


Maybe anyone knows what is correct vacuum value or what is correct rpm speed with MAP sensor unplugged? Does ECU maintain idle speed with IACV connected and MAP disconnected?

Thnx in advice.

Best regards, Marudny.
Title: Re: Vacuum value at idle (rough idle problem).
Post by: richardcbf on 02 May, 2016, 09:41:05 PM
Sorry, don't know the vacuum values, but have you checked the ECT Sensor?
Title: Re: Vacuum value at idle (rough idle problem).
Post by: FireBladerDk on 02 May, 2016, 10:33:22 PM
I have never had any real experience with abnormal idle and high fuel consumption on my biffer, so my input might not be worth much.

Could it be one of the cylinders not having  efficient ignition?

Did you compare spark plug conditions when you replaced with new ones?

And come to think of it. I did once manage to run a full tank empty in less than one hour. Reason was using almost full throttle all the way.

 :041:   ... Fred
Title: Re: Vacuum value at idle (rough idle problem).
Post by: Robo on 02 May, 2016, 10:49:39 PM
If it runs bad only on cold start I'd recheck the IACV motor again even unplug it and see what happens, I'm sure you know what the IACV motor does .

Does it run and idle up when hot  :261:

I know of a few MK1's that ran rough with faulty IACV motors.

A faulty or unplugged ECT sensor won't do a thing until the bike reaches running temp.

I wouldn't mess withe the throttle bodies as I think you are looking in the wrong place.

Is the MIL light flashing  :261:

Have you erased the DTC  :261: If not do it and see what happens. :028:
Title: Re: Vacuum value at idle (rough idle problem).
Post by: Marudny on 02 May, 2016, 11:16:05 PM
*Originally Posted by richardcbf [+]
Sorry, don't know the vacuum values, but have you checked the ECT Sensor?

Honestly? No. I just realized I focused on throttle body cause someone (i'm second owner of that bike) unscrewed throttle regulator screws and caused vacuum leak. Tomorrow i'll check resistance of ECT in different temperatures.

*Originally Posted by FireBladerDk [+]
I have never had any real experience with abnormal idle and high fuel consumption on my biffer, so my input might not be worth much.

Could it be one of the cylinders not having  efficient ignition?

Did you compare spark plug conditions when you replaced with new ones?

And come to think of it. I did once manage to run a full tank empty in less than one hour. Reason was using almost full throttle all the way.

 :041:   ... Fred

Yes, i compared spark plugs.  All four looks identical - rich mixture.

I drained full tank in 1,5 hour (not in CBF). Long highway and avg speed 200km/h, but trust me now i achieved 9 liters per 100km with avg speed 100km/h. It's impossible for me.

*Originally Posted by Robo [+]
If it runs bad only on cold start I'd recheck the IACV motor again even unplug it and see what happens, I'm sure you know what the IACV motor does .

Does it run and idle up when hot  :261:

I know of a few MK1's that ran rough with faulty IACV motors.

A faulty or unplugged ECT sensor won't do a thing until the bike reaches running temp.

I wouldn't mess withe the throttle bodies as I think you are looking in the wrong place.

Is the MIL light flashing  :261:

Have you erased the DTC  :261: If not do it and see what happens. :028:

Yep, no problems with starting (cold, warm, hot). It's a reason why excluded ECT sensor. Always the same problem - rough idling. Today i did throttle balance with unplugged and plugged IACV - no difference in idling. As I mentioned below - mess with throttles someone done before me (i've had vacuum leak through too much unscrewed screw).

MIL light works typical. Goes out after pre-start diagnosis and never light / flash during the ride.

I've tried to reset DLC. No changes.
Title: Re: Vacuum value at idle (rough idle problem).
Post by: Robo on 03 May, 2016, 10:37:16 AM
Buy another set of throttle bodies. I would be interested how you think you would adjust the ones you have :261:

A set of bodies can be bought for around 100

The ECT won't be the fault. if someone has messed around with the throttle bodies I think you answer is there.
 :028:
Title: Re: Vacuum value at idle (rough idle problem).
Post by: J-man on 03 May, 2016, 11:43:07 AM
The Choke function keeps ON ?
A wild guess though.
Title: Re: Vacuum value at idle (rough idle problem).
Post by: Marudny on 03 May, 2016, 11:48:17 AM
*Originally Posted by J-man [+]
The Choke function keeps ON ?
A wild guess though.

How recognize choke function? Higher idle when cold? Exhaust gas has typical smell for rich mixture at idle, what suggests choke still on.

I'm car engineer, not motorcycle. I met different behavior of choke function.

*Originally Posted by Robo [+]
Buy another set of throttle bodies. I would be interested how you think you would adjust the ones you have :261:

A set of bodies can be bought for around 100

The ECT won't be the fault. if someone has messed around with the throttle bodies I think you answer is there.
 :028:

I'm seriously thinking about new bodies. ECT will be fault when receives something unexpected - I know.

I'm car engine engineer and I can only use my car experience and anything I found in cbf service manual and forums.

What I think and found:
1. Map sensor takes average pressure from cylinders 2,3,4. Ecu calculates injection time based on map sensor. 1st cylinder vacuum is using to idc (vacuum on 1st has different characteristic than others). So I'm sure that cylinders 2,3,4 should have identical vacuum. 1st one also (why not?).
2. ECU has no possibility to calculate different injection time on each cylinder (one map sensor, one oxygen sensor).
3. IACV increases or decreases amount of air for four cylinders simultaneously (one valve only - no possibilty to provide different amount to each cylinder).

4. I unplugged MAP sensor and connected vacuum meter to the throttles and read values (mentioned in first post).

Cause i couldn't find vacuum values i made an experiment.

5. I screwed regulators to max. I read values, was about 680 to 710 mbars, and RPM about 980. Conclusion - ECU doesn't correct RPM using IACV when MAP sensor is unplugged.
6. I unscrewed regulators until I heard vacuum leak. Next screwed 1/4 of twist to seal leak and read values - about 840 - 860 mbar, and RPM about 1300.
7. So we have adjustment range from 710 to 840 mbar.
8. At first try i set 800 mbar, got 1150 rpm, engine run stable.
9. I connected vacuum lines and map sensor, engine run stable at idle, but was lazy with setting an idle sped. It looked like IACV was set to learned value providing to much air and gently closing to set RPM. I wasn't sure if ECU learn new IACV value (it should, but i don't know PGM-FI as much).
10. I reconnected  vacuum meter and set vacuum to 775 mbar and 1070 RPM.
11. Idle is still rough, but it's better than before.

I'm not sure if i set vacuum value properly. I don't know how much IACV is opened when MAP is unplugged (or maybe iacv is fully closed or fully open?). Electronically speaking IACV is a stepper motor when it's unplugged it stays at last position.

I'll test ECT and IACV with service manual.
Title: Re: Vacuum value at idle (rough idle problem).
Post by: Bifferman on 03 May, 2016, 03:24:14 PM
Maruudny, you sound pretty knowledgeable on this stuff.  A bit beyond my level of diagnostics.  I would have to resort to 20% common sense + 70% working through the service manual + another dose of common sense to bring me up to 100%.

I did wonder though if it is worth anything at all would show up on the OBDiagnostics especially as your plugs appear to show a rich mixture.  At  least the MKII has Iridium plugs as standard so that's a good start.

Watching with interest.

Andy
 :149:
Title: Re: Vacuum value at idle (rough idle problem).
Post by: Marudny on 03 May, 2016, 05:41:09 PM
ECT checked - works good.

I've think about fuel pressure. If is higher than expected - injectors will give more fuel in amount of time. That explain rough idle and higher fuel consumption. I'll have to check it.

Regards, Marudny.
Title: Re: Vacuum value at idle (rough idle problem).
Post by: rarch on 03 May, 2016, 08:12:11 PM
Are you aiming for a too low idle speed, I believe it should be around 1200 +/- 100 rpm.  My bike idles at 1300 rpm.
Title: Re: Vacuum value at idle (rough idle problem).
Post by: Robo on 03 May, 2016, 09:14:49 PM
*Originally Posted by J-man [+]
The Choke function keeps ON ?
A wild guess though.

= IACV Motor
Title: Re: Vacuum value at idle (rough idle problem).
Post by: Marudny on 03 May, 2016, 09:41:09 PM
*Originally Posted by rarch [+]
Are you aiming for a too low idle speed, I believe it should be around 1200 +/- 100 rpm.  My bike idles at 1300 rpm.

I don't know a position of iacv valve. Maybe I should aim 1200 rpm with map unplugged. But 1200 rpm is almost at the end of vacuum regulation range. I believe that iacv should raise rpm to optimal speed.
Title: Re: Vacuum value at idle (rough idle problem).
Post by: Marudny on 03 May, 2016, 09:53:30 PM
*Originally Posted by Robo [+]
= IACV Motor

Iacv looks good. Increases idle at cold and decreases with raising coolant temperature.

I bought used throttle body with air box, fuel rail and injectors and all sensors.

But nothing explains higher fuel consumption. I'm sure that vacuum subsystem is sealed. Idling is rough without iacv correction. Tps is correct. Mixture is richer than expected. Everything goes to fuel pressure regulator. Typical fuel pump gives 5 bars. Fuel pressure regulator set it to 3,5 at idle and 4 - 4,5 when needed.

It explains everything - higher consumption (pressure is higher than needed), rough idle (too much fuel at idle). Richer mixture and dark spark plugs

Injectors has minimal open time. Below that they can't operate properly. Even if injectors have minimal open time calculated for 50 psi fuel pressure (as service manual says) which gives 3.5 bars, at 5 bars they gives much more fuel which is uncorrectable. In cars engine management injectors are chosen in that way. Minimal open time at idle.

I'll check fuel pressure at the weekend.

Regards Marudny.
Title: Re: Vacuum value at idle (rough idle problem) [SOLVED]
Post by: Marudny on 05 May, 2016, 11:20:52 AM
Guys, case solved!

I measured fuel pressure at idle. Service manual says 50psi at idle (3.5 bar). I've got ~70 psi (4.8 bar). After reducing to 50 psi engine started to run smoothly. Additionally measured AFR at idle should be near to 14.7. Got 12 ;-)

New fuel pump is comming, i'll change her and set vacuum again to minimal values (screw regulators to max and set to highest vacuum).

Thnx for every answer and help!

Title: Re: Vacuum value at idle (rough idle problem).
Post by: J-man on 05 May, 2016, 12:14:57 PM
Congratulations  :152:
and thank you for sharing your hunt.  :028:
Title: Re: Vacuum value at idle (rough idle problem) [SOLVED]
Post by: FireBladerDk on 05 May, 2016, 06:47:42 PM
*Originally Posted by Marudny [+]
...  After reducing to 50 psi engine started to run smoothly. ...

How did you reduce the fuel pressure during that test?

Title: Re: Vacuum value at idle (rough idle problem).
Post by: Marudny on 05 May, 2016, 07:22:25 PM
*Originally Posted by FireBladerDk [+]
How did you reduce the fuel pressure during that test?

I have got adjustable fuel pressure regulator with pressure meter and baypass.

Something like this:
http://m.ebay.com/itm/231824730304

Regards, M.
Title: Re: Vacuum value at idle (rough idle problem).
Post by: Bifferman on 05 May, 2016, 08:14:03 PM
*Originally Posted by Marudny [+]
I have got adjustable fuel pressure regulator with pressure meter and baypass.

Something like this:
http://m.ebay.com/itm/231824730304 (http://m.ebay.com/itm/231824730304)

Regards, M.

As I said you are way out of my league (higher than).  I can see some of us coming to you for some diagnostic advice as and when we need it :028:

Andy
 :149:
Title: Re: Vacuum value at idle (rough idle problem).
Post by: Marudny on 05 May, 2016, 09:07:58 PM
I have some general knowledge about electronic fuel injection and don't have typical motorcycle knowledge... but if I could help, I'll be glad.

Again, thnx for suggestions!

Regards, M.


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Title: Re: Vacuum value at idle (rough idle problem).
Post by: rarch on 05 May, 2016, 10:05:52 PM
Well done.

I've heard of pumps with internal strainer/filter getting clogged up which reduced the fuel flow, symptoms were lack of high speed but bike could maintain a constant lower speed.

Do you have any idea what would cause a pump to deliver at a higher pressure, could it be a blocked pressure relief valve within the pump?  Maybe it can be cleaned...
Title: Re: Vacuum value at idle (rough idle problem).
Post by: J-man on 05 May, 2016, 10:49:09 PM
Edit: so it must give 3.5 bar no matter rpm? Or is that just 1 point of reference?
Title: Re: Vacuum value at idle (rough idle problem).
Post by: Marudny on 05 May, 2016, 11:44:29 PM
*Originally Posted by rarch [+]
Well done.

I've heard of pumps with internal strainer/filter getting clogged up which reduced the fuel flow, symptoms were lack of high speed but bike could maintain a constant lower speed.

Do you have any idea what would cause a pump to deliver at a higher pressure, could it be a blocked pressure relief valve within the pump?  Maybe it can be cleaned...

All constructions I've met are designed with external fuel pressure regulator (which is vacuum operated - to increase fuel pressure). Relief valve is only a kind of safety valve. It's my first time with return less fuel system.

In CBF fuel pressure regulator is in the pump assembly, probably relief valve does FPR function. If not, there should be fuel pressure regulator. Pump always deliver higher pressure (typically 5 bar). After pump is FPR which regulates pressure. It's very simple construction - spring and diaphgram. Spring weakens with time and FPR delivers higher pressure than set.

I'll check at the weekend :)

*Originally Posted by J-man [+]
Edit: so it must give 3.5 bar no matter rpm? Or is that just 1 point of reference?

Service manual says 50 psi at idle. It's very hard to measure fuel pressure while riding :) But pressure is constant in all conditions, flow is higher while riding (injectors have longer opening time).
Title: Re: Vacuum value at idle (rough idle problem).
Post by: Mark91 on 21 May, 2020, 10:31:43 PM
Hello,

Yes, I know, the Honda does not recommend the throttle body sync, but has anybody tried to do it?
What is it the correct method ?

Thanks.