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Discussion Starter · #1 ·
Been trying to diagnose P1301 Misfire level causing emissions increase along with P0300 P0301 P0302 misfire codes that return a few miles after erasing the codes. Just happened to look at the live data section in the scan tool and notice that short term fuel trim Bank 1 Sensor 2 is always at 99.2%. That can’t be right? And which is sensor 2? There is one before the cat, another one after the cat and a third one after the muffler.
 

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Pull your coils and check for corrosion that could be hurting spark performance, beyond that here are the definitions from the Lotus manual..



Misfire
P0300 Random/Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0302 Cylinder 2 Misfire Detected
P0303 Cylinder 3 Misfire Detected
P0304 Cylinder 4 Misfire Detected
Description
A misfiring cylinder can be detected by analysing crank speed variation. As a result of a combustion event there
will be a net acceleration of the crankshaft. Subsequent to a misfire event the engine will decelerate over the
period following the missed cylinder event.
Speed changes can be characterised by observing changes in the time period for a fixed angle of rotation after
firing events. A significant change in this period, assessed by comparison to previous periods, may be attributed
to misfire on a known cylinder.
Component connections
Connector Description ECU Pin ECU Connector
1 Supply Voltage Coil 1 Coil 2 Coil 3 Coil 4
2 Ignition Coil Feedback 22 22 22 22 52 Way
3 Coil Output (Logic) 52 26 47 48 52 Way
4 Ground
Malfunction Criteria
The operation of all the misfire codes is the same, the last digit relates to the misfire involved i.e. a code P0303
indicates there is a problem with coil number 3. P0300 indicates the misfire is random and not linked to one
particular cylinder.
Enable Criteria:
• Battery voltage between 10 – 16 V
• Coolant temperature between -10 – 120°C (14 – 248°F)
• Engine speed between 660 – 8010rpm
• Engine speed transient > 15rpm
• Altitude < 8000 ft (2438 m) / Baro > 756mbar
• Fuel level > 5 litres (1.3 US gallons)
• Engine load between 15 – 48% depending on engine speed
Disable Criteria: DFCO enabled (Deceleration Fuel Cut Off)
Monitor: Continuous
Limp home:
• Limit maximum engine speed to 6000 rpm
• Return the fuel system to open loop
• ECU may deactivate two cylinders, the misfiring cylinder and it’s matched other i.e. 1 & 4 or 2 & 3.
Potential failure modes:
• Injector related codes, as these can cause misfire codes to be set.
• VVT or VVL codes set
• Sensor connector and wiring for signs of corrosion or loose connections
• Spark plug / Cylinder compression
• Cam timing / Damage to rocker arm assembly
sn_

Misfire P1301
P1302
P1301 Misfire level causing emissions increase
P1302 Misfire level causing catalyst system damage
Description
When the engine misfire reaches a high enough percentage the engine emission output levels can exceed the
allowed limits, this will produce the fault code P1301. If the misfire percentage is high enough and there is a
possibility that the catalyst may be damaged then code P1302 will be set.
See misfire faults P0300, P0301, P0302, P0303, P0304
Notes:
• The MIL will flash for a 1302 fault code
• The MIL will be illuminated if the 1301 fault is present for 2 consecutive trips.
 

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Discussion Starter · #3 ·
No corrosion at the coils and even when I swap them between cylinders, it's always #1 and #2 that set the codes.
 

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Is your car totally stock? If not, what has been touched?
 

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Discussion Starter · #5 ·
It's got a turbo with a Unichip controller that I temporarily removed for testing so it has the stock tune. Fuel injectors have been tested and are good. Smoke machine shows no vacuum leaks. New stock plugs. Valve adjustment. Good compression.
 

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How does it idle? If driven lightly does it pull smoothly thru the rev range? Any hesitation? Do you have any means to measure the exhaust primary tube temps (assuming you don't have a log style manifold)? If your issue seems to be cylinders 1 and 2 you may have a injection driver issue (since you are spliced hopefully it's just a bad connection).
 

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Discussion Starter · #7 ·
It idles just fine. Driven lightly it feels pretty smooth. I've been taking it on 6 mile test ride loops, half on the highway and at a steady 60, it can be smooth one second, then it may miss a couple of times bad enough that the car bucks a little. Not clear on injector drivers. Aren't the injectors driven by the factory ECU?
 

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Yes, the injector drivers are in the factory ECU. You said you took out your Unichip so the ECU is running the entire show at this point. The fact that it can run smooth then every now and again stumble and buck may point to a wiring or ground issue. If you have cut and spliced the injector/ignition wires at any point in the harness revisit all of the splices to check integrity. Also every point of grounding on the motor to chassis must be inspected (a faulty ground can cause some strange running conditions).
 

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Discussion Starter · #9 ·
Whoever installed this did a hack job on the wiring harness so yes, that could be an issue. I was just surprised when I found the short term fuel trim Bank 1 Sensor 2 is always at 99.2%. And what is with the 3rd O2 sensor?
 

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There are a lot of possible causes of the short term fuel trim reading high. What injectors are you running (stock, aftermarket)? Injector wiring issues that are causing the stumble could be leaning out the bank as a whole, if your building low boost on the stock ecu program the ecu has no way to compensate other then short term trim (most likely this is the case), leak in exhaust upstream of the O2 sensor causing a lean reading that the ecu is trying to compensate for.
 

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Discussion Starter · #11 ·
It has RC injectors and I didn't see any exhaust leaks with a smoke machine. Thanks for the suggestions, might have to take it to somebody if I don't fine something soon myself.
 

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Good luck, I would focus on the splices in the harness.
 

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Bank 1 sensor 2 is not valid data. The only sensor you care about is bank 1 sensor 1. You can stop the goose hunt as it relates to the bank 1 sensor 2.

Misfire: Check coil packs and apply di-electric inside the boot. Check cams for intake wiping.

-Phil
 

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Can't see #1 or #2 intake... assuming they're fine, then I'l look real hard at the pigtails for the RC injectors. I read through too quickly and missed the injector swap bit... A poor injector connection will trip a s 1301... Most common 1301s are injector adaptors, coil arcing, and cam wiping...

-Phil
 

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Discussion Starter · #17 ·
I'm just getting back to the car. Checked the pigtail wiring connections to the harness and the solder joints seem fine but the polarity is reversed on cylinders 2 and 4. As in, the green ground wire from the harness goes to the black pigtail wire on 1 and 3, but to the red wire on 2 and 4. Does that matter, as injectors are just solenoids without polarity? Or is this enough to trigger the 1301 code?

 

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hello, I have same problem with an 02 Bonneville (99.2 short fuel trim) but my error codes are different , they are p0103,p0102 ,p0101 all have to do with MAF sensor. symptoms sound the same , will run smooth then starts cutting out ,sometimes dies then runs fine , mas air flow in the datastream will read 307.17 g/s most of the time then will read correctly between 3.75g/s and 4.30g/s , have replaced all the sensors except o2 sensor behind the cat. replaced the fuel system, the ECM seems to check out good . thinking problem may be in the PCM. the o2 sensor output voltage (B1-S2)will vary as it should , but the short term fuel trim (B1-S2) remains 99.2?
I think we might have the same problem even though the error codes are different
 

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How much PSI are you running ? what are CC injectors are they ? Is this a force feed turbo kit with a unichip ? if it is a force feed turbo kit with a unichip i would think about do a something different like DRS or BOE for ECU
 
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