Engine Misfires on cylinders?

Tiny
NEED MY CAR
  • MEMBER
  • 1999 FORD EXPEDITION
  • 5.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 188,000 MILES
OBD says cylinders 7 and 8 are misfiring. I first need to switch 8 and 6 to determine if it's the plugs or the coils?
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Wednesday, April 1st, 2020 AT 7:56 AM

50 Replies

Tiny
KASEKENNY
  • EXPERT
I would suggest switching the coils and plugs one at a time with a cylinder on the opposite bank just to make sure they swap sides. Due to these two cylinders being next to each other we cannot rule out a head gasket issue so we may need to do a compression check if the plugs, coils, or injectors are not the issue.

Here are guides on how to do these tests:

https://www.2carpros.com/articles/how-to-test-engine-compression

https://www.2carpros.com/articles/head-gasket-blown-test

Let me know if you have questions or what you find and we can go from there. Thanks
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Wednesday, April 1st, 2020 AT 8:11 AM
Tiny
BMDOUBLE
  • EXPERT
Please have a look at the lower cowl panel seal. At my dealership we usually have to remove it and replace the one-sided sticky seal because the original is flattened and does not give the upper rubber cowl seal a positive seal against the hood thus making water leak onto the top of the engine, and consequently into the plug holes and onto the coils.
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Wednesday, April 1st, 2020 AT 6:37 PM
Tiny
GEOR2683
  • MEMBER
  • 1999 FORD EXPEDITION
  • V8
  • AWD
  • AUTOMATIC
  • 133,000 MILES
Test show misfire on cylinder 8. I changed spark plug and coil and still has misfire. Whats wrong?
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
MERLIN2021
  • EXPERT
When you changed the plug and coil, did you replace the boot? And was the plug fouled?
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
GEOR2683
  • MEMBER
What do u mean by fouled plug? And the boot do u mean the piston?
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
MERLIN2021
  • EXPERT
By fouled, is the plug black? Wet? Melted electrode? Anything abnormal about it? Did you change all plugs or just #8?. Is it a single coil pack, or coil on plug system? Were the plug wires if coil pack all changed? Coil on plug, where the Boots under the coils changed? And can you feel the injector clicking with the engine running? You may need a fuel pressure and injector leakdown test.
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
ASHWHIZ
  • MEMBER
  • 1999 FORD EXPEDITION
  • V8
  • 2WD
  • AUTOMATIC
  • 16,000,000 MILES
Acts like engine misfire but it does it when its going to shift. All coils fine
it does it on reg. Driving
will not do it going fast or real slow
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
If the check engine light is on let run the codes tis guide will help

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If not, check fuel pump pressure to confirm it is within spec. If a tune up hasn't been done for a long time look at this guide.

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine

and

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Please run down these guides and report back.
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
JERBRO
  • MEMBER
  • 1999 FORD EXPEDITION
  • V8
  • 2WD
  • AUTOMATIC
  • 98,000 MILES
Have a misfire on # 4 according to my tester.
P 304 is the code, is it my coil or fuel injector an how do I test it? Please Help!
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
The injectors in these vehicles are very dependable. Chances are the coil pack is bad. You can check to see if it is getting spark. Also, I have seen the rubber boot actually go bad and cause the coil to short.

Let me know what you find.
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
BILL
  • MEMBER
  • 1999 FORD EXPEDITION
I have a '99 Ford Expedition (4wd) with 5.2L V-8 (GAS) engine and it as been thru the routine Ford maint per the book at proper intervals.

Recently the truck started running very-rough and then the "Engine Needs Service Soon" alarm-light came on.

Seems roughest at idle and at all shift points as well.

Put my OBD2 on and confirmed CODE P0304 for #4 Cylinder Misfire

Please advise on the most likely things you would to check out in order please. Advice appreciated!

Thx

Bill
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
BRETT ANDERSON
  • MEMBER
Check to see if you have spark. Could be a bad coil, wire or spark plug. If those three are good you more than likely have a bad injector. If thats not it you don't want to know what it is.$$$$$$$
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
JAEDAV12
  • MEMBER
  • 1998 FORD EXPEDITION
  • 5.4L
  • V8
  • 2WD
  • AUTOMATIC
  • 178,000 MILES
The truck has been misfiring on and off for about a month. Changed out all spark plugs, ignition coils, and ignition coil pigtails. Checked for vacuum leaks and there were none detected and when checking for misfires there are none found. There is a heated o2 sensor code but I think it s due to a leak in the exhaust. What other possible causes can cause the truck to run the way it is?
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

You have done a lot already. Are you certain there are no vacuum leaks? There is a vacuum hose that runs off the back of the throttle body and will have a 90 bend in it. They commonly dry rot and leak.

If that isn't the case, what code are you getting for the sensor? Also, are you sure it is the engine and not a transmission issue? I ask only because there are no misfire codes.

Keep in mind that the O2 sensor could cause an issue, but I would think you would see a code and the exhaust leak, as you already know, can be the cause. So I would really like to know the code you have.

Next, have you checked fuel pressure to confirm there isn't an issue? Pressure that is too high or too low can also cause a misfire.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Here are the specs for pressure:

1998 Ford Truck Expedition 2WD V8-5.4L SOHC VIN L
Pressure
Vehicle Powertrain Management Fuel Delivery and Air Induction Fuel Pump Fuel Pressure Specifications Pressure, Vacuum and Temperature Pressure
PRESSURE
Engine Running .................... 193-310 kPa (28-45 psi)
Key ON Engine .................... 242-310 kPa (35-45 psi)

Also, a partially restricted exhaust system (converter) can cause a misfire often along with a loss of power.

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

______________________

If you have a live data scanner, could you let me know what the short term fuel trims are?

Let me know.
Joe
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
JAEDAV12
  • MEMBER
P0133, P0135 and I ll have to check that hose.
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
See pic 1 for P0133 possible causes. You are very possibly right with the exhaust leak. If you look at pic 2, it indicates possible causes of the P0135. That is different and not related to a power issue. I believe the two are related for the same reason, a lack of power. Check the connector for corrosion, damage, skinned wires, disconnected or pushed in pins or anything out of the ordinary.

Let me know what you find.

Joe
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
JAEDAV12
  • MEMBER
Checked that vacuum line you talked about and the line was fine. But I ll get to checking that connection and is that what could possibly cause the lack of power? It s usually around 35-45 mph.
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Based on the codes, I feel that is a good place to start. If the computer is trying to adjust air fuel mixture based on faulty readings, anything is possible. If your scanner shows live data, let me know what the short term fuel trims are and see if it is running the fuel system in a closed loop when at operating temperature.

Joe
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
JAEDAV12
  • MEMBER
I ll check the trims tomorrow.
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Sounds like a plan. Let me know what you find or if you have other questions.

Take care,
Joe
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Thursday, November 12th, 2020 AT 8:55 AM (Merged)

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