Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: omegod on 02 November 2016, 20:25:56
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Trying to help out one of our brethren Tony who has long running issues with his 2.5, it's had new plugs, leads and dis pack but the following persists , in his own words:
"The symtoms are as follows, missfire under light throttle. (seem harder to start from cold in the last week) running seems to slightly improve as the engine warms up, when driven hard the "miss" seems to clear and the firing is normal until desired cruising speed is reached them as the throttle is backed off the "miss" returns. mpg has taken a beating down to 13 MPG around town"
I have the unmentionable diagnostic device and have no intention of using it for programming but am happy to look at any monitors/values to try and narrow down what may be wonky so would be grateful if you guys could advise what we need to look at and what the normal values would be, lambda switching , fuel trims and anything else useful etc
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A physical check for an air leak between the Mass Air Flow Meter and inlet manifolds is your next step. That includes all of the vacuum pipes.
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If no one comes forward with any more suggestions........
Check that the temperature reported by the coolant temperature sensor (CTS) and air intake sensor are credible.
Check the fuel trims
How well does it run with the MAF unplugged?
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And adding to the 'vac leak' theory - an incorrectly-fitted plenum can cause leaks, as can trapping the long hose that runs down the NS (coolant for the throttle body, so I recall) also can be the cause of things. I had an issue with vac leak, when I went to fit a new CTS, as mentioned above, I noticed the coolant pipe did rather 'spring' out as I lifted the plenum. I'll never know if it was in any way trapped, or causing a slight leak, but it's possible, and has been known. You do somewhat need three hands to replace the plenum, some days. Also the o-rings slipping is another known one. U think I've 'glued' them in place with a dab of vaseline / oil before, to ensure they are seated right. :).
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Coolant temp sensor readings would also be on my list.
Do also check the large breather pipe for split and/or damage, seen one before with very similar symptoms which was caused by this.
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Plenum is seated properly , Tony has sprayed a fair bit of carb cleaner around with no increase in revs. What should the coolant temp sensor be showing as healthy also lambdas , what should they switch to and from?
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Ecu coolant temp should be around 92 degrees C ie a smidgen higher than the gauge ;)
Much below or above suggests a failed or thermostat, open if lower, closed if higher...
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Plenum is seated properly , Tony has sprayed a fair bit of carb cleaner around with no increase in revs. What should the coolant temp sensor be showing as healthy also lambdas , what should they switch to and from?
I'm not saying you're wrong, but I sprayed a fair bit of carb cleaner, too (getting underneath the plenum with a spray I'd say is close to impossible, the gap you have to aim for is tiny) with no effects, but I'm sure there was still a slight, if only slight weep/gap. Only cured when I re-seated it after a major service. (also doing the CTS, which definitely helped)
As I say, not saying you're wrong, just for future reference/future readers of this thread, it can be a bugger. :)
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Managed to swing by Tony's today between meetings, Code 19 present but I doubt that would cause such running issues. It's stinging of fuel from the exhaust and unplugging MAF made no difference. I took some data snapshots which I'll stick up when I get chance
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Managed to swing by Tony's today between meetings, Code 19 present but I doubt that would cause such running issues. It's stinging of fuel from the exhaust and unplugging MAF made no difference. I took some data snapshots which I'll stick up when I get chance
That's a reason on its own to change cranksensor. Wouldn't be the first cranksensor fault to cause poor running.
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OK here's a wee snapshot if it helps, car was at idle and temp matched what was on the gauge. Anything obvious standing out ?? I did get some live data recorded if it's any use. Will see if I have a spare crank sensor to try
Control Unit:
KW82 protocol initialized.
ECU ID= HH 90492382 261203588 1037350104 3
Measuring blocks information:
Identifier 0D
Battery Voltage 13.8 V
Immobiliser Signal Received
Immobiliser Active
TPS Signal (Throttle Position Sensor) 0.55 V
Simulated Idle Position Active
Simulated Full Load Switch Inactive
Mass Air Flow Sensor 0.88 V
Mass Air Flow Sensor 18 kg/h
Coolant Temperature 1.66 V
Coolant Temperature 66 °C
Intake Air Temperature 3.53 V
Intake Air Temperature 20 °C
Engine Type 6 Cylinder
Transmission Coding Automatic Transmission
Park/Neutral Switch P - N 0V
A/C Information Switch (Air Conditioning) Inactive 0V
A/C Compressor Switch (Air Conditioning) Inactive 0V
Telltale (Check Light) Off 12V
Fuel Pump Relay Active 0V
Spark Angle before TDC (Top Dead Centre) 2 °CA
Ignition Coil Cyl. 1+4 (Cylinder) Load
Ignition Coil Cyl. 2+5 Load
Ignition Coil Cyl. 3+6 (Cylinder) Load
Knock Signal Inactive
Knock Retard 0 °CA
Secondary Air Pump Relay Inactive 12V
EGR Valve (Exhaust-Gas Recirculation) Inactive
EGR Position Feedback (Exhaust Gas Recirculation) 0.76 V
Fuel Tank Ventilation Valve 0%
O2 Sensor 1 790 mV
O2 Sensor 2 283 mV
O2 Sensor Loop 1 Closed
O2 Sensor Loop 2 Closed
Air/Fuel Ratio 1 Lean
Air/Fuel Ratio 2 Rich
O2-Loop 1 Integrator 132 Steps
O2-Loop 2 Integrator 138
O2-Loop 1 BLM Idle (Block Learn Map) 160 Steps
O2-Loop 2 BLM Idle (Block Learn Map) 25 Steps
O2-Loop 1 BLM Partial Load (Block Learn Map) 117 Steps
O2-Loop 2 BLM Partial Load(Block Learn Map) 154 Steps
Hall Sensor Inactive
Engine Speed Pulse Active
Engine Speed 693 RPM
Idle Air Control 147 Steps
IAC Integrator (Idle Air Control) 132 Steps
IAC Adaptation Slope (Idle Air Control) 140 Steps
IAC Block Learn (Idle Air Control) 131 Steps
Desired Idle Air 15 kg/h
Actual Value Idle Air 15 kg/h
Desired Engine Idle Speed 670 RPM
Injection Pulse 3.8 ms
Engine Load Signal 1.5 ms
TPS Load Signal (Throttle Position Sensor) 0%
Vehicle Speed Pulse Not Received 12V
Vehicle Speed 0 km/h
Intake Manifold Valve 1 Inactive 12V
Intake Manifold Valve 2 Inactive 12V
Torque Control Inactive
A/C Cutoff Relay (Air Conditioning) Inactive 12V
Diagnostic Request Inactive 5V
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Jeesus Jon it's all greek to me, ??? but like to say a big thank you for all your help in trying to sort out this matter your a star :y
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I'm no expert but seems to be a BIG difference in Side 1 v Side 2 ..
O2 Sensor 1 790 mV
O2 Sensor 2 283 mV
O2 Sensor Loop 1 Closed
O2 Sensor Loop 2 Closed
Air/Fuel Ratio 1 Lean
Air/Fuel Ratio 2 Rich
O2-Loop 1 Integrator 132 Steps
O2-Loop 2 Integrator 138
O2-Loop 1 BLM Idle (Block Learn Map) 160 Steps
O2-Loop 2 BLM Idle (Block Learn Map) 25 Steps
O2-Loop 1 BLM Partial Load (Block Learn Map) 117 Steps
O2-Loop 2 BLM Partial Load(Block Learn Map) 154 Step
Is there any way you can read the injector timings ?? If it's not an air-leak then possibly one (or more) injector(s) is (are) out of sync with the rest ??
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Just been on a twenty mile run and tried leaving the box in sport mode ( not driving it hard) seemed to run a lot better which ties in to some of my previous posts that the "missfire" has a direct relation to engine revs.