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Loss of power over 6k rpm, Mis at idle

 
Old 09-27-2018, 09:00 PM
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Post Loss of power over 6k rpm, Mis at idle

Hey all, I am in the process of getting my car ready for a MK kit in the next month or so. Of course this is when problems start to show themselves with the car. Hoping to pick some of your brains and diagnose this.

The past week or so I have noticed the car feeling not quite as "fast" as it normally does. I know this is a slow car but I have daily driven it for over a year and have a pretty accurate butt sensor. Up around 5800-7000rpm the car is noticeably louder (has more of a roar to it) and feels to plateau quite a bit. Today driving on the highway I decided to see what the car does a higher speed, at the top of fourth the rpm climbs at a hysterically slow rate. By 6800ish the car is practically no longer accelerating. The car has also developed a very slight mis at idle. I have put new plugs and plug wires in it and no change.

Doing some research and a bit of a educated guess my assumptive is that there is a crack in the header somewhere that may be confusing the O2 sensor which is resulting in a loss of power up top. I have inspected under the car and found no leaks in the exhaust, the previous owner has wrapped the header so I haven't gotten to properly inspect it. When the car gets louder at a high rpm it seems at if its coming from in-front of me which is what leads me to believe a crack in the header. Car is a 1.6 with 130,000. Recent timing belt and water pump job.

Thanks
- Becker
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Old 09-27-2018, 09:25 PM
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If you momentarily block off the exhaust with your hand (and a cloth or such) during a cold start you should be able to bring out the exhaust leak a bit more.

How recent was the TB job? Did it start after that? Do you have a wideband and aftermarket ecu or are you just about totally stock?
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Old 09-27-2018, 11:16 PM
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Originally Posted by ridethecliche View Post
If you momentarily block off the exhaust with your hand (and a cloth or such) during a cold start you should be able to bring out the exhaust leak a bit more.

How recent was the TB job? Did it start after that? Do you have a wideband and aftermarket ecu or are you just about totally stock?
TB job was done like 2 weeks ago. It started and ran fine immediately after that. 100% stock right now, I have a innovate mtx-l and I am currently soldering together my MS3 to go in the car in the next week or so.
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Old 09-28-2018, 09:30 AM
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Id confirm the timing was correct if the TB job was that recent. Unless the problem was there before, but it's still worth looking at.
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