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Noddy OBD2 question; and low idle speed.
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Noddy OBD2 question; and low idle speed.
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08 Oct 2015 15:47 #153223
by Rhinoman
Its running quite rich have you given it a compression test? when was the last time it was serviced?
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08 Oct 2015 17:12 #153228
by Sheepish
Service about 3.5K miles ago. Are you thinking air cleaner or something else?
I have a compression tester somewhere, I'll dig it out. What about it suggests a possible problem there?
Is it likely this would be contributing to the sudden rough running?
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08 Oct 2015 19:55 - 08 Oct 2015 19:57 #153241
by Rhinoman
There aren't too many reasons for it running rich, poor engine efficiency could be one, a bad fuel pressure regulator another. A blocked air filter should have more effect under load than at idle but your fuel trims are reasonably stable. I would think that the poor idle is caused by the Idle Speed Controller being unable to add enough air to compensate. Unfortunately that is where an OBD2 tool falls short, its not able to read the parameters associated with idle, such as Target Idle Speed and ISC duty cycle, those can only be accessed using an 'OBD1' tool.
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Last edit: 08 Oct 2015 19:57 by
Rhinoman.
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08 Oct 2015 19:59 #153242
by Rhinoman
What readings are you getting for manifold pressure and VE/engine load at idle? Are your CTS and IAT readings credible?
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08 Oct 2015 22:51 #153276
by Sheepish
Idle between 750-800 RPM
VE between 47.1% and 49.2%
Intake Pressure between -0.83 and -0.81 bar
CTS between 87 and 89C
IAT between 20 and 22C
Short fuel between -0.8 and 3.1
Long fuel between -10.2 and -7.1
Stopped for petrol tonight, and it was a pig to start again. And tried starting from warm just now after taking these figures and again it seems to need throttle to start.
I cleaned out the PCV valve earlier, squirted some carb cleaner through it, just because it's easy. It seems to idle at higher revs now but still quite lumpy.
For my education what is it about the fuel trims that tells you it is running rich?
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09 Oct 2015 22:27 - 09 Oct 2015 22:29 #153322
by Rhinoman
A negative number means that the ECU is running less fuel to compensate for a rich condition. The limit is around -14% but in reality if you get to -10% then you are way richer than you should be and at that point the ECU may struggle to be able to adjust the idle speed correctly.
Is that VE at idle? if so then its way too high. Your intake pressure seems awry too I would expect around 300mbar at idle, what does it read with the engine off?
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Last edit: 09 Oct 2015 22:29 by
Rhinoman.
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18 Oct 2015 20:59 - 18 Oct 2015 21:00 #153884
by Sheepish
Quick update in case it's of use to anyone. Took the EGR valve off again and it was jammed open. Another 24 hour soak in carb cleaner didn't help much. So I pushed the valve closed and refitted without the cable so it wouldn't try to open again. I now have a smooth tickover. Idle inlet pressure is down to .37 bar and efficiency to 33%. Long fuel trim still up at aroun -13%
Will give Suzuki a ring to find out what a new valve costs but given they are north of £200 on Amayama I think it's going to be nasty!
Last edit: 18 Oct 2015 21:00 by
Sheepish. Reason: Spelling
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19 Oct 2015 08:28 #153898
by Sheepish
So I was perusing a parts diagram for the EGR components and noticed Suzuki sell blanking plates for the EGR valve and the pipe into the manifold for where an EGR is not fitted. My main concern with not having one working was the higher combustion temperatures reducing exhaust valve life, but perhaps I don't need to be concerned? If I did decide to run without one, for a while at least while I save up for a new valve! Is there anyway to tell the ECU I don't have one, so I don't get an MIL on all time telling me something is wrong with the exhaust recirculation?
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19 Oct 2015 08:45 #153899
by j999pre
I have a used egr valve if your interested? Which engine have you?
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19 Oct 2015 18:26 - 19 Oct 2015 18:28 #153933
by Rhinoman
The blanking plate is used on 'General Export' models that have no emissions control equipment, if you remove the EGR on yours the ECU will throw a code and adopt a fail safe mode. The software is different so there is no easy cheat.
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Last edit: 19 Oct 2015 18:28 by
Rhinoman.
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20 Oct 2015 20:39 #154055
by Sheepish
j999pre wrote: I have a used egr valve if your interested? Which engine have you?
M13aa, the DOHC. Given the one I have seems to have died at under 50K miles I'm not sure I'd use a s/h one, but if yours isn't for that engine it would save me the dilema
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20 Oct 2015 21:19 #154066
by Rhinoman
Intake pressure is a lot closer but engine efficiency should be around 5 to 10%. You don't get a lot of cylinder filling at idle, if the ECU thinks there is that much air then it will add a lot of fuel, you should be in closed loop though, can you read that flag? is the O2 sensor switching? it sounds like you have an issue that is outside of those tested by EOBD, if the ECU has detected an undetermined fault or a fault that there is no code for then it will not enter closed loop; It is a bit tricky to be precise with EOBD data because it isn't complete.
If there isn't an issue then the LTFT should come down after a drive. The EGR valves are usually quite reliable, yours may have been coked up because of the rich running, its also going to kill the cat and O2 sensors.
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Noddy OBD2 question; and low idle speed.
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