Cylinder five misfire code

CA7922303

MEMBER
2001 HYUNDAI SANTA FE
2.7L
V6
2WD
AUTOMATIC
325,000 MILES

Engine code check at Oreily's shows #5 misfire. Idles rough, runs about right on highway. Have changed wires, plugs, injectors, crank/cam sensors, both computer units under dash on hump. Please advise. Thanks.

Wednesday, March 9th, 2022 AT 7:56 AM

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,867 POSTS

Hi,

You have replaced nearly everything. If it is still a cylinder 5 misfire, you may have a compression issue.

Because of the mileage, which is where I would start. Here is a link that explains how to test compression:

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

The directions specific to this vehicle are attached below. Additionally, the manufacturer's specifications for compression are listed.

Let me know what you find or if you have other questions.

Take care,

Joe

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Wednesday, March 9th, 2022 AT 3:45 PM

CA7922303

MEMBER
149 POSTS

Compression test shows #5 cylinder off by about 40% of other cylinders. Checked it several times to verify. Head gasket was changed, and head surfaced less than 6,000 miles ago. I had trouble with exhaust cam on that head getting it lined up with marks. There is no water in oil, no smoke from tailpipe and no coolant loss. Is it possible that cams not aligned correctly could cause cylinder misfire and a random cylinder's misfire code? Thanks.

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Sunday, March 20th, 2022 AT 4:26 PM

JACOBANDNICKOLAS

MECHANIC
109,867 POSTS

Hi,

That big of a variation will cause a misfire. If it was a timing issue, you would see it in other cylinders as well.

So, it sounds like the head gasket isn't the issue. That leaves the valves. When the head gasket was replaced, were the valves inspected? You could have one that is not sealing off and allowing the lower compression.

Let me know.

Joe

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Sunday, March 20th, 2022 AT 7:39 PM

CA7922303

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149 POSTS

Machine shop resurfaced head and did not mention any issues with valves. If I remember they said head was tested for leakage? What is typical from a machine shop? Thanks.

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Wednesday, March 23rd, 2022 AT 5:31 PM

JACOBANDNICKOLAS

MECHANIC
109,867 POSTS

Hi,

Let's look at this from a different point of view. I need you to retest compression on cylinder 5. Do it dry first, and then do what is called a wet compression test. To do this, place about two tablespoons of motor oil into the cylinder and then test compression.

If this is a ring-related issue, the oil will increase the compression by eliminating some of the space to bypass the rings.

Let me know.

Joe