Cylinder issues, codes P0303 and P0304

Tiny
CLINGLEY91
  • MEMBER
  • 2010 FORD E-SERIES VAN
  • 5.4L
  • V8
  • 2WD
  • AUTOMATIC
  • 190,000 MILES
Passenger side valve head. Changed plug fuel injector and coil. Compression tested 150 on all 4 cylinders on that side. However on the left side head (drivers side ) significantly lower 5 and 6 where about 120 cylinder 7 and 9 are at 90.
but no scan tool is picking anything up for the head on that side?
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Saturday, October 10th, 2020 AT 3:38 PM

4 Replies

Tiny
KASEKENNY1
  • EXPERT
This is rare but I suspect you have cylinder balancing issues. The way the vehicle picks up misfires is by not seeing crank shaft acceleration after each cylinder fires. So when there is a misfire the crank does not accelerate as expected and it starts to count misfires. Then it monitors the o2 sensors for how much fuel is in the exhaust to confirm this as their will be unburned fuel in the exhaust.

So you could have an issue on 3 and 4 but the fact that you have low compression on the other bank, we need to solve that and then retest the misfires on 3 and 4.

I assume the vehicle is running rough so we need good compression on all cylinders before we address fuel and spark

Let's run a leakage test to find out where the compression is going. I suspect a head gasket issue so if you want to run that test first then that is fine.

Here is a guide to help with that:

https://www.2carpros.com/articles/head-gasket-blown-test
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Saturday, October 10th, 2020 AT 4:18 PM
Tiny
CLINGLEY91
  • MEMBER
The van will start and with no issue. Will idle with almost no hesitation but it didn't seem to want to go up my hill pedal to floor only would do 50 mph up hill. Has not stalled out yet at all. Starts every time.
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Saturday, October 10th, 2020 AT 4:30 PM
Tiny
CLINGLEY91
  • MEMBER
It does sputter at lower rpm and hesitates to accelerate.
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Saturday, October 10th, 2020 AT 4:31 PM
Tiny
KASEKENNY1
  • EXPERT
Okay. That is pretty indicative of low compression. So let's address that issue and go from there. Clearly that is a larger issue then the misfire codes on the other bank.

We have to prioritize them and address the most pressing. It is like it you have a splinter in one finger and a cut on another. You are going to address the cut before you get the splinter out. Let me know what happens with the leak down test or head gasket test and we can go from there. Thanks.
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Saturday, October 10th, 2020 AT 5:45 PM

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