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Offline Marudny

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Vacuum value at idle (rough idle problem).
« 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.

Offline richardcbf

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Re: Vacuum value at idle (rough idle problem).
« Reply #1 on: 02 May, 2016, 09:41:05 PM »
Sorry, don't know the vacuum values, but have you checked the ECT Sensor?
(No one ever said on their deathbed, "Gee, I wish I had spent more time alone with my computer." Danielle Berry.) http://hmpg.net/

Offline FireBladerDk

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Re: Vacuum value at idle (rough idle problem).
« Reply #2 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

Offline Robo

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Re: Vacuum value at idle (rough idle problem).
« Reply #3 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:
If theres a gap i can get through it !!!

Some people pay for an IAM... I am mad.....

Offline Marudny

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Re: Vacuum value at idle (rough idle problem).
« Reply #4 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.

Offline Robo

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Re: Vacuum value at idle (rough idle problem).
« Reply #5 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:
If theres a gap i can get through it !!!

Some people pay for an IAM... I am mad.....

Offline J-man

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Re: Vacuum value at idle (rough idle problem).
« Reply #6 on: 03 May, 2016, 11:43:07 AM »
The Choke function keeps ON ?
A wild guess though.

Offline Marudny

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Re: Vacuum value at idle (rough idle problem).
« Reply #7 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.
« Last Edit: 03 May, 2016, 01:35:42 PM by Marudny »

Offline Bifferman

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Re: Vacuum value at idle (rough idle problem).
« Reply #8 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:

Offline Marudny

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Re: Vacuum value at idle (rough idle problem).
« Reply #9 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.

 


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