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Post by lowender on Nov 7, 2023 20:06:42 GMT
Mk1 1.8 with MS2 pnp: Failed mot emissions first time (fast idle lambda), passed on retest, but only after tester ran the car at over 4000 rpm for a few minutes to "get the cat hot". Since then it's running very rich, 9:1 afr at 2500 rpm, 10 at idle, runs terribly. Today I replaced the 7 year old wideband sensor, no difference. Tried loading different tunes from different times, no difference. What could be causing this? injectors, iat sensor, coolant temp sensor? Something seems to have happened as a result of the tester revving the nuts off it. Any suggestions?
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Post by atlex on Nov 7, 2023 21:11:53 GMT
I would check sensor calibrations. Specifically, MAP and IAT as those have the highest impact on fueling. Share a log and check what you're seeing - it could be the map or IAT sensors have failed and are now out of their normal voltage range (i.e they are giving a failure calibration), or they've come out of calibration. I don't think keeping the engine at 4K would do anything to the sensors so don't blame him unless he did something else too  |
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Post by lowender on Nov 7, 2023 21:42:43 GMT
Thanks for the response. I've checked the sensor calibrations in tuner studio, they're all correct, although the MAP calibration is custom. I'll get a composite log tomorrow and see what's what.  |
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Post by atlex on Nov 8, 2023 8:49:55 GMT
also check the FPR - that could cause higher fuel pressure if it failed. I'd expect an FPR to fail rich (safe) rather than lean.
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Post by lowender on Nov 8, 2023 13:23:13 GMT
MAP reading koeo is 98 kPa, with engine running it stays at a constant 77.3 kPa regardless of rpm. Is this normal?
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jon
Chats A Lot
Posts: 270
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Post by jon on Nov 8, 2023 19:17:01 GMT
No - it should vary with throttle / load...
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Post by dadbif on Nov 9, 2023 7:47:44 GMT
Has your MAP sensor pipe become trapped or burnt through?
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Post by lowender on Nov 9, 2023 10:13:59 GMT
Has your MAP sensor pipe become trapped or burnt through? I've checked it from end to end, it's all ok. I suspect the sensor in the ecu. |
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Post by lowender on Nov 9, 2023 16:51:26 GMT
So I swapped the FPR for one I had in the shed - made no difference. I'm getting weird readings in tuner studio from both the MAP sensor and IAT sensor, so I've ordered new ones. I also checked the base timing and it's spot on at 10 degrees.
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Post by atlex on Nov 9, 2023 19:04:51 GMT
MAP reading koeo is 98 kPa, with engine running it stays at a constant 77.3 kPa regardless of rpm. Is this normal? definitely wrong, it should read 30-40kpa at idle and increase with throttle opening - and then come back down as the engine speeds up and pulls more vacuum... 77kpa indicates a really weak idle vacuum - at WOT it should be over 95kpa unless you have huge intake restrictions. maybe a leaky MAP hose also.. |
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Post by lowender on Nov 13, 2023 19:15:39 GMT
All sorted now, normal service resumed. Despite it being the first thing I checked, it was indeed the MAP hose that was the problem. In a senior moment, I had only checked it for holding vacuum, and not for air flow. I gave it another look and It was severely restricted in a few places. New pipe fitted, and it’s all good. Thanks for the help.
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Post by atlex on Nov 13, 2023 21:36:13 GMT
happy ending!! :-)
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le sigh