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#4098292 - 02/21/21 09:30 PM Help! I have an unsolvable misfire problem
Zepherius Offline
Stranger

Registered: 01/28/21
Posts: 8
Loc: Boston MA
I was wondering if anyone could help me. I've been having a misfire on cylinder number 2 for a very long time and I can't figure out what the heck it is. More often than not the car seems to run with no issues however sometimes at idle it tends to run rough for 5 to 10 minutes sometimes longer then it'll go away for a long period of time and then it'll randomly return. I also get an engine light every time this happens especially when I'm at a red light for a long time. However after I start moving sometimes the engine light will automatically turn itself off. I changed the spark plugs, coils, and fuel injectors however it was still misfiring. I also confirmed that it's not an intake manifold problem as As there are no cracks that could lead to air leaking out. I ended up bringing it to a shop and they told me that I had 4% down low compression in that cylinder. At this point I assumed It's a rocker and or lifter problem. I took off the valve cover to inspect the Rockers and lifters and it seems like there's absolutely nothing wrong with them. I'm completely at a loss if anyone could help me that would be great. Thanks.


Edited by Zepherius (02/21/21 09:32 PM)
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#4098298 - 02/21/21 11:06 PM Re: Help! I have an unsolvable misfire problem [Re: Zepherius]
Bangster Offline

Poobah

Registered: 11/30/01
Posts: 9332
Loc: Tucson Az
What code do you get? P0302, or something more specific?
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#4098306 - 02/22/21 01:12 AM Re: Help! I have an unsolvable misfire problem [Re: Bangster]
Zepherius Offline
Stranger

Registered: 01/28/21
Posts: 8
Loc: Boston MA
P0302 is the only code that I get


Edited by Zepherius (02/22/21 01:14 AM)
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#4098336 - 02/22/21 07:43 AM Re: Help! I have an unsolvable misfire problem [Re: Zepherius]
Rootintootin Offline
Climber

Registered: 02/26/08
Posts: 612
Loc: North Carolina
I see the problem. Your car is black. I heard black cars have this problem.

All seriousness aside, I would look at the connector(s) for that cylinder. You know, the ones for the coil and the injector. I had an ABS problem for years that was caused by an intermittent bad connection of the pump motor connector. When the wires were connected directly to the motor without the 2 pin connector body, problem solved. At least try cleaning the contacts in the pigtails.
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97 CVPI(Ex. Tampa PD #715), 141K miles, performance Torque converter, J-modded valve body. Monroe Gas Magnum Severe Duty shocks, Ported Plenum and 70mm FRPP Throttle body

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#4098344 - 02/22/21 09:06 AM Re: Help! I have an unsolvable misfire problem [Re: Rootintootin]
Zepherius Offline
Stranger

Registered: 01/28/21
Posts: 8
Loc: Boston MA
yes but how does that explain the lower compression?
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#4098346 - 02/22/21 09:50 AM Re: Help! I have an unsolvable misfire problem [Re: Zepherius]
Bangster Offline

Poobah

Registered: 11/30/01
Posts: 9332
Loc: Tucson Az
The compression was 4% lower than the next lowest? That shouldn't be an issue. You are looking for 135 psi or better and no more than a 25% variance (so if the highest is 150, then the lowest should be 113 psi but that still seems bad).

Or it was 4% of the highest or others? That would be bad, 6 psi...
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#4098348 - 02/22/21 10:04 AM Re: Help! I have an unsolvable misfire problem [Re: Bangster]
Zepherius Offline
Stranger

Registered: 01/28/21
Posts: 8
Loc: Boston MA
its defiantly not at 6psi. it is 4% lower than the next lowest.

my biggest worry is that its a worn out piston ring or valve (I hope its not)


Edited by Zepherius (02/22/21 10:09 AM)
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#4098372 - 02/22/21 11:05 AM Re: Help! I have an unsolvable misfire problem [Re: Zepherius]
Bangster Offline

Poobah

Registered: 11/30/01
Posts: 9332
Loc: Tucson Az
Unless there is a 25% variation with the highest to the lowest, then it is likely not mechanical like a valve. If the lowest is 4% lower than the next lowest, and that one is 25% lower than the highest one, then maybe.

Usually a connector issue will show as a P0352 but not always. Since you have replaced all the plugs, coils and injectors, that does leave the connector, the wiring, the PCM.
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#4098374 - 02/22/21 11:16 AM Re: Help! I have an unsolvable misfire problem [Re: Zepherius]
Rootintootin Offline
Climber

Registered: 02/26/08
Posts: 612
Loc: North Carolina
Someone has to be the lowest. My Harley only has 2 cylinders and and one is lower than the other. But that's about 12 years after my last top end work. Or maybe a 12 year old car should be in probably better than new condition.

Did the shop give you a readout of all 8 cylinders or only tell you you had one that was lower? Do you have the raw data or only their report of that one cylinder?

Here's an example that is almost tailor-made for your situation. They seem to put some emphasis on 15%, highest to lowest.

https://troubleshootmyvehicle.com/ford/4.6L-5.4L/how-to-test-engine-compression-2

Maybe you ought to find one of those miracle in a can additives to see if it could break loose a stuck ring or whatever they do to make your motor like new.
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97 CVPI(Ex. Tampa PD #715), 141K miles, performance Torque converter, J-modded valve body. Monroe Gas Magnum Severe Duty shocks, Ported Plenum and 70mm FRPP Throttle body

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#4098388 - 02/22/21 12:12 PM Re: Help! I have an unsolvable misfire problem [Re: Rootintootin]
Zepherius Offline
Stranger

Registered: 01/28/21
Posts: 8
Loc: Boston MA
I don't have raw data. just the report
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#4098424 - 02/22/21 12:58 PM Re: Help! I have an unsolvable misfire problem [Re: Zepherius]
Rootintootin Offline
Climber

Registered: 02/26/08
Posts: 612
Loc: North Carolina
I don't want to rehash my whole saga over my ABS connector, but it went from isolated, short duration to where it was non-functional for over a year. I finally got so tired of looking at the light that I let a shop have a look. They said they had the equipment to do all the things that Ford would do with the NGS tester. 15 minutes after turning the car over to them, the tech came out and said he couldn't get it to respond and would I come back and have a look.

Turns out he was baffled by the 2 releases on the ABS motor connector. Instead of releasing the wiring like you or I would do, he yanked the wires out of the connector. I guess I was getting what I paid for. I couldn't get the wires back in as he had gutted the innards. I just plugged the 2 wires back directly in and put the connector in my pocket. After some Oh wells and thanks anyways, I left as there didn't seem to be anything else they could do.

I know I had that connector off numerous times, sprayed with contact cleaner, blah, blah, blah. I was sure there was good contact.

On the drive home, I sure was surprised to see my ABS light go out. Been working fine ever since. I would replace the connector if I could find one without having to buy another 20+ year old car just to get it.

The moral of the story is there wasn't anything wrong with any part except a 39ยข piece of 23 year old plastic.


Edited by Rootintootin (02/22/21 12:59 PM)
Edit Reason: grammar
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97 CVPI(Ex. Tampa PD #715), 141K miles, performance Torque converter, J-modded valve body. Monroe Gas Magnum Severe Duty shocks, Ported Plenum and 70mm FRPP Throttle body

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#4098468 - 02/22/21 01:55 PM Re: Help! I have an unsolvable misfire problem [Re: Zepherius]
RF_Overlord Online   content

Poobah

Registered: 12/14/02
Posts: 7409
Loc: MA
To put it bluntly, 4% low ain't squat.

A can of Techron or Regane in the tank or a Seafoam treatment is an inexpensive try. Even if it doesn't fix the problem, you at least will know the engine's innards are clean.
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#4099044 - Yesterday at 12:10 PM Re: Help! I have an unsolvable misfire problem [Re: Zepherius]
Danger2manifold Offline
Member

Registered: 02/23/19
Posts: 145
Loc: Hard Hittin' New Britain, CT
4% is well within normal limits, no need to worry about it. The cause of your issues is something else
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