Misfire at Idle

[Popeye775 16]

Hey guys,

 

I’m starting a new thread with this problem very detailed. It is in my other thread but I wanted everything on the top post so I could try to get any advice possible and have everything in one spot.

 

Issue: Lean misfire at idle (16-18 AFR with a burbly idle)

 

Things changed: CTS, fuel injectors, vacuum lines, spark plugs, idle air screw o-ring, o2 sensor

 

Things tested: ISV and wiring, CTS and voltage tested wiring (with car running), CO pot wiring (voltage tested with car running), resistance of the air temp sensor and CO pot, spark, fuel pressure, smoke test, AFR, o2 sensor and wiring, co pot and air temp sensor at the ECU end of the harness, main grounds, timing.

 

Details: the car runs lean at idle (15-18 AFR) and has a misfire like sound while idling. While cruising or driving with open throttle, the AFR is pretty decent and the misfire seems to go away. Here’s where it gets interesting. During the first 30-60 seconds on starting, the car will run at a 12-13 AFR and idle smooth. It will also do this warmed up, with the CTS UNPLUGGED. But as soon as it’s plugged back in, it’ll lean out and start to burble again. I will attach a video of the noise as well so you guys can hear it. The CTS is unplugged in this video for the first part of it. As soon as you hear it start to stutter, is when the CTS was plugged back in. Any help would be appreciated

 

 

 

 

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[KarlosG60 2]

Sounds to me like a problems/holes in the exhaust line.

[Popeye775 16]

Sounds to me like a problems/holes in the exhaust line.

Hi sir, are you talking about some sort of exhaust leak somewhere?


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[KarlosG60 2]

3 hours ago, Popeye775 said:

Hi sir, are you talking about some sort of exhaust leak somewhere?


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Correct. Did you check it out?

That was the first thing I think about when I see and listen the video. 

[Popeye775 16]

Correct. Did you check it out?
That was the first thing I think about when I see and listen the video. 

I did smoke test the car and couldn’t see any visible vacuum or exhaust leaks. But will check again! The only thing I’m curious of is how that could explain how the car idles fine with the CTA unplugged if it were an exhaust leak?


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[KarlosG60 2]

On 10/3/2020 at 3:05 PM, Popeye775 said:

I did smoke test the car and couldn’t see any visible vacuum or exhaust leaks. But will check again! The only thing I’m curious of is how that could explain how the car idles fine with the CTA unplugged if it were an exhaust leak?


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I don't know what is CTA. The idle valve?

[Popeye775 16]

I don't know what is CTA. The idle valve?

CTS** sorry sir mistyped


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[Popeye775 16]

Hey guys for anyone following this thread,

so here is the plan for the Corrado. I am extremely bummed that this car has just been sitting, but I am going to try and see if anybody near me - that owns a corrado or use to - has a spare stock ECU I can borrow to plug into my car and see if a different ECU solves the issue. IF it does, then I will move my chip over into that ECU and see if the problem persists. If it does, then I know it is the chip, if everything is fine, then I will know it was the ECU. If the different ECU doesn't work, then I am going to trace the red wire going from ECU to the injectors to see if there are any breaks in that wire anywhere. I'm not assuming that it has any breaks in the wiring, but it could. Three questions,

First: Is there a way I can test for breaks in that red wire before trying to rip anything apart? Just to avoid ripping the harness apart.

Second: The harness connector clip plastic for my injector (plugs into the injector harness) has a break in the plastic. It still plugs into the injector harness just fine, but could this have allowed any loose connection in one of the wires? I think at this point I am just searching for any little thing that could be wrong/causing this issue.

Finally: Does anybody know of a way I can test my ECU out to see if it is bad or not? I am not assuming the ECU is bad just because the car starts up first try every time, and doesn't really run lean/misfire while cruising or driving, but Im assuming it could still be a possibility.

Thank you to all who have helped thus far, and to those that continue to help try to solve this issue.


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[Popeye775 16]

Found something interesting that I wanted an opinion on. With CTS unplugged, I can richen up the AFR to an about ~12-13 and the car will idle fine. This is all with CTS still unplugged. If I try to turn the CO pot to lean it out a bit to get it to around that 14 range, the car starts to sputter and sound misfirish and begin to lean out. Does this mean anything to anyone?


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[seanl82 23]

9 hours ago, Popeye775 said:

Hey guys for anyone following this thread,

so here is the plan for the Corrado. I am extremely bummed that this car has just been sitting, but I am going to try and see if anybody near me - that owns a corrado or use to - has a spare stock ECU I can borrow to plug into my car and see if a different ECU solves the issue. IF it does, then I will move my chip over into that ECU and see if the problem persists. If it does, then I know it is the chip, if everything is fine, then I will know it was the ECU. If the different ECU doesn't work, then I am going to trace the red wire going from ECU to the injectors to see if there are any breaks in that wire anywhere. I'm not assuming that it has any breaks in the wiring, but it could. Three questions,

First: Is there a way I can test for breaks in that red wire before trying to rip anything apart? Just to avoid ripping the harness apart.

* Easy to do, you'll need a multimeter though. Disconnect the battery first, and either test continuity with the probes at each end of the red wire or if you can't reach both ends, short the red with another wire that goes to/from the same place to create a loop. 

Second: The harness connector clip plastic for my injector (plugs into the injector harness) has a break in the plastic. It still plugs into the injector harness just fine, but could this have allowed any loose connection in one of the wires? I think at this point I am just searching for any little thing that could be wrong/causing this issue.

*Possible, but if both pins look to be seated properly and are fairly tight, it shouldn't be an issue.

Finally: Does anybody know of a way I can test my ECU out to see if it is bad or not? I am not assuming the ECU is bad just because the car starts up first try every time, and doesn't really run lean/misfire while cruising or driving, but Im assuming it could still be a possibility.

* Not sure on the diagnostic setup on a G60 and if it has a 2+2, but if so you should be able to connect it to VCDS even if you don't get many options. Worth looking around the menus to see what they say if possible.

Thank you to all who have helped thus far, and to those that continue to help try to solve this issue.


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Edited October 10, 2020 by seanl82

[Popeye775 16]

8 hours ago, seanl82 said:

 

Hi sir, thank you for the reply. I will continuity test the wires today. That will narrow things down even more. I don't think you can use VCDS for G60. Just because the digifant has a different plug than OBDII, and from searching VCDS I only found ones that plug into OBDII ports sadly. Unless I am searching wrong haha

[seanl82 23]

32 minutes ago, Popeye775 said:

Hi sir, thank you for the reply. I will continuity test the wires today. That will narrow things down even more. I don't think you can use VCDS for G60. Just because the digifant has a different plug than OBDII, and from searching VCDS I only found ones that plug into OBDII ports sadly. Unless I am searching wrong haha

I think it has a 2+2. You can read certain codes using the OBD2 and an adaptor. I don't think you can read much, but if you know someone close that has one you should be able to connect and at least see basic info which may give you an idea if the ECU is working.

https://www.ebay.co.uk/itm/143738230852

 

[Popeye775 16]

I think it has a 2+2. You can read certain codes using the OBD2 and an adaptor. I don't think you can read much, but if you know someone close that has one you should be able to connect and at least see basic info which may give you an idea if the ECU is working.
https://www.ebay.co.uk/itm/143738230852
 

I actually do know someone with one! I will give it a shot. Thank you sir


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[Popeye775 16]

So here is an update:

Misfire is fixed. The issue was the spark plug wires - that I had just changed not too long ago - but the car still runs lean. Around 14-18 AFR at idle, 14 - 15 cruising, and 13 - 14.5 under throttle. It does drop down to 13.5 - 14 AFR at idle with the CTS unplugged. Can this still be the wiring from ECU to injectors, or ECU itself? Possibly the chip in the ECU? I am still working on trying to hook something up to Digifant to check for any computer codes as well. But if there are any new ideas to test out, that would be more than helpful! Thank you all in advance 

Any suggestions welcome!

[tonedef 9]

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