Chasing misfires and need help

5.0 Hatch

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I've been trying to identify the source of misfires on my 01 Cobra and I'm not real sure where to go at this point.

It started with a very very consistent misfire at idle. I couldn't feel it but it was noticeable in the exhaust note. I went ahead and ordered a complete set of 8 Accel coils and replaced them a long with motorcraft plugs. Right away the idle sounded like it had cams and the miss was all over the place. I took it for a 5 mile drive and when I returned, the idle was the smoothest I've ever had since owning the car. After sitting for a week, I started it up and the misfires are back.

No check engine light and the car only has an offroad x and slp catback.

I have a feeling it's cop related but is there anyway to know for sure? I also now know motorcraft cops are the way to go.
 

5.0 Hatch

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Here's a video at idle with the stock coils. You can hear the consistent rattle sound in the exhaust note.

Here's a video at idle right after installing Accel coils

Here's a video with accel coils after a 5 mile drive
 

BlackStang00

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Any codes? Also throw those coils in the trash and get oem coils. All others are junk. Do you have a way of datalogging? That will help narrow the issue.
 

DSG2003Mach1

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I think it would be worth investing in something to datalog. Forscan has an app (havent tried it) or you can run it on a laptop for free. You just need to the OBD2 connector. I would want to try and look at the misfire counter and such to be sure that really is what you're hearing.
 

5.0 Hatch

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I think it would be worth investing in something to datalog. Forscan has an app (havent tried it) or you can run it on a laptop for free. You just need to the OBD2 connector. I would want to try and look at the misfire counter and such to be sure that really is what you're hearing.
I actually do have a OBD2 bluetooth connector and checked codes using the torque app. Forscan never crossed my mind. I'll check into it.
You’re kind of limited on diagnosing in that case. How did the old plugs look? Is your frps functioning?
I pulled the plugs last night and they seemed fine. Keeping in mind they might have 30 miles at most on them. I'm not sure how to check the frps.
 

DSG2003Mach1

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I actually do have a OBD2 bluetooth connector and checked codes using the torque app. Forscan never crossed my mind. I'll check into it.

I pulled the plugs last night and they seemed fine. Keeping in mind they might have 30 miles at most on them. I'm not sure how to check the frps.
I havent used the torque app - can it datalog? if so is there an option for a misfire counter?

I believe there is a Forscan lite option for the phone thats free (for an iPhone anyway). The free version on a laptop has very strong datalogging
 

BlackStang00

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I’ve never been a fan of torque but I know a lot of people like it. Imo Forscan is better.

As far as testing the frps, it either works electronically or it doesn’t. You can rule out the electronic side but pull the vacuum line off and check for gas. And check all of your wiring. I mean all of it. And check for vacuum leaks too.

I had a similar problem on and old 00 gt I had not too long ago. My problem was o2 sensor related. Just food for thought.
 

01yellercobra

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If the FRPS was bad you'd get a code and more than likely have wet plugs. When mine blew it flooded the engine. I didn't have gas in the vacuum line because it had been sitting, but I could smell it. When I pulled the FRPS I was able to blow through it. You're not supposed to be able to do that.

Are you tuned? If so do you have a hand held? You can use that to datalog. It would be odd to have a severe enough miss that you can hear/feel it at idle, but not set any codes.
 

5.0 Hatch

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I had a similar problem on and old 00 gt I had not too long ago. My problem was o2 sensor related. Just food for thought.
I've installed brand new o2's as well. I forgot to mention that.
If the FRPS was bad you'd get a code and more than likely have wet plugs. When mine blew it flooded the engine. I didn't have gas in the vacuum line because it had been sitting, but I could smell it. When I pulled the FRPS I was able to blow through it. You're not supposed to be able to do that.

Are you tuned? If so do you have a hand held? You can use that to datalog. It would be odd to have a severe enough miss that you can hear/feel it at idle, but not set any codes.
No tune and no tuner. Assuming I can use Forscan with a bluetooth ob2 scanner, it appears I can pull the misfire count. I'll try that later today.

The FRPS is definitely a possibility. At completely random times, I do get a good amount of smoke out the exhaust at idle.
 

5.0 Hatch

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I was unable to get forscan to work but used torque pro and getting this. The car is running so rich I had to take it out the garage. Also, the longer the car is in the on position and not started, the longer it cranks over before starting
 

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BlackStang00

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So both banks are running rich, but it’s not overly rich. Can you datalog fuel pressure? Have you tried cleaning your maf?
 

5.0 Hatch

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How did this end? I have a miss at idle. More like a little stumble compared to these issue. But how did this end? What was the outcome?
Hey man. I haven't resolved the issue completely.
1. I used Forscan and determined there was no actual misfire.
2. I finally got a consistent code for Bank 1 being rich but no other codes indicating a sensor problem

My uneducated guess is it's a fueling issue of some sort. I've changed the o2's, cleaned the MAF, checked for vacuum leaks, even swapped out the injectors and while the warm start issues are gone, it still stumbles when idling.

Outside of the idle problems, it drives perfect.
 

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