chasing down po300
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Joined: Jun 2008
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chasing down po300
The transmission project is finally completed and now I find I have an engine issue. Car runs great cold and decent warm, but after 20 minutes or so of continuous driving it starts to misfire. No backfiring or popping, just seems to drop a cylinder every now and then. You also notice it at idle, when stopped in gear. It progressively worsens until it is running quite rough and throws po300 code.
I'm planning on testing the injectors as this feels like a fuel problem to me. However I wonder if there is a reliable way to also test the coil and ICM. It isn't going to do much good to take them off and have them tested because the problem occurs only when hot.
While discussing this with one of the vendors the suggestion was made that the car may be staying in open loop mode. How can this be verified? I only have Autoxray scanner and it says all is well and the car does pass emissions.
Anyone else run into this situation?
I'm planning on testing the injectors as this feels like a fuel problem to me. However I wonder if there is a reliable way to also test the coil and ICM. It isn't going to do much good to take them off and have them tested because the problem occurs only when hot.
While discussing this with one of the vendors the suggestion was made that the car may be staying in open loop mode. How can this be verified? I only have Autoxray scanner and it says all is well and the car does pass emissions.
Anyone else run into this situation?
Le Mans Master
Joined: Nov 2006
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From: Greenwood Indiana
2021 C4 of the Year - Modified Finalist
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Did you replace all of the plugs or just that one? Did you use the same style plugs?
I almost got those Bosch for mine, but the guy at the store said they don't work well in the LT-1s. (I got Champions instead)
I almost got those Bosch for mine, but the guy at the store said they don't work well in the LT-1s. (I got Champions instead)
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Pro
Joined: Jun 2008
Posts: 610
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Just that one. I happened to have an extra new one from when I replaced them recently.
That probably happened when I installed them. That one came out of #6 cylinder. First time working on this engine and I dropped them a few times. (#8 was a barrel of fun) Didn't notice it because it was getting dark when I did it.
That probably happened when I installed them. That one came out of #6 cylinder. First time working on this engine and I dropped them a few times. (#8 was a barrel of fun) Didn't notice it because it was getting dark when I did it.
