4/6 cylinders misfiring. Low compression 1+2 30 psi

[Markfranklin]

I am working on determining what to replace first. The car was a bit sluggish. Then cylinder 2 misfire code appeared, followed by 1,3 and random misfire codes.

Initial diagnostics only reveals those codes and low compression on cylinders 1+2

I am planning to replace timing chain and cam phasers due to lack of other ideas. It doesn’t appear to be leaking any fluid, but I do consider a blown head gasket a possibility. It does not have white smoky exhaust, and spark plugs were very dirty when removed and replaced.

Is there any other thing I should consider like the fuel injectors or vvt solenoid first?

Edit: 163,000 miles. New plugs and coils already.

Edit 2: I can’t afford a 20k new engine, but I can afford to do 3 months of labor and a 5-7k used engine. So I am trying to do anything short of that first. I am making decisions based on things that would fail in the order of:
1 the car started out running normal but a bit sluggish in the last 5k miles,
2 fuel economy has not significantly changed during this time,
3 very recently, the car is shaking severely and backfiring indicating a lack of complete/ balanced combustion.
4 after replacing plugs and coils, the plugs were very dirty, codes all came back the same
5 the only information the dealer has added to what I could gather is; low compression cylinder 1+2 of around 30 psi and should be 120psi


I appreciate the responses so far. Thank you.

 

[Action]

Post actual codes, please.
How many miles?
A compression test should be done before tearing into the engine.

Due to lack of better ideas you are going to under take replacing the timing chairs!
Why don't you diagnose the problem first?

Action

 

[Markfranklin]

Post actual codes, please.
How many miles?
A compression test should be done before tearing into the engine.

Due to lack of better ideas you are going to under take replacing the timing chairs!
Why don't you diagnose the problem first?

Action

Bc I could sit there and do nothing, or start fixing probable causes. And compression test revealed low compression on cylinder 1+2. 163,000 miles. Timing chain seemed reasonable due to it hasn’t had a new one since I got it and I got it at 80k miles. Thank you for your response

Edit: I have not got it back in my possession since the dealer told me $21,000 for a new engine so that is why I am fine with tearing into it.

 

[akras]

Don't do random things before trying a proper diagnosis. Get a borescope, pull out spark plugs, and inspect the cylinders' walls and the tops of the pistons for damage. Also, you should be able to see valves opening and closing as you turn the crankshaft. Try to check the condition of valve seats and valves themselves. Timing should be way off to reduce compression. Also, does it have the cold start rattle? Very bad phasers can affect timing more that the chain.

______________________________

 

[Markfranklin]

Don't do random things before trying a proper diagnosis. Get a borescope, pull out spark plugs, and inspect the cylinders' walls and the tops of the pistons for damage. Also, you should be able to see valves opening and closing as you turn the crankshaft. Try to check the condition of valve seats and valves themselves. Timing should be way off to reduce compression. Also, does it have the cold start rattle? Very bad phasers can affect timing more that the chain.

It does rattle a bit at startup, but it matches what seems to be an issue with the turbos based on what I could gather.

Something is severely off regarding ignition/timing as the car is shaking quite severely and even backfiring some. The spark plugs were very dirty and I haven’t found anything related to a blown head gasket yet other than the low compression in cylinder 1+2. Which was reported by the dealer as the only symptom other than the 5 missfire codes it is displaying. Cylinder 1,2,3,6 and random missfire.

If a video of the startup would help give some guidance, I can add that. From my perspective the engine is a lost cause without a rebuild, so that is why I am beginning with replacing things that would be common in a rebuild process.

There is no code relate to camshaft position sensor or any other codes in the last 50k miles other than these.

Thank you for your response.

 

[Action]

It does rattle a bit at startup, but it matches what seems to be an issue with the turbos based on what I could gather.

Something is severely off regarding ignition/timing as the car is shaking quite severely and even backfiring some. The spark plugs were very dirty and I haven’t found anything related to a blown head gasket yet other than the low compression in cylinder 1+2. Which was reported by the dealer as the only symptom other than the 5 missfire codes it is displaying. Cylinder 1,2,3,6 and random misfire.

The timing chain and gear assembly do not impact compression.

Was the lack of compression tested before or after the timing chain replacement.
If after, it is possible the cams are not in sync with the crankshaft. Or valves are not fully closing..
If before the chain replacement would not correct a low compression.

Low engine cylinder compression is caused by
Excessive valve wear, or valves not fully closing
Excessive piston ring wear
Engine damage
Leaking head gasket

Action

 

[driller]

Low engine cylinder compression is caused by
Excessive valve wear, or valves not fully closing
Excessive piston ring wear
Engine damage
Leaking head gasket

I would not rely on someone else's (dealer) compression test.

Do your own compression test individually on all cylinders under the same circumstances, both dry and wet.

Then perform a cylinder leak down test on each cylinder to determine probable loss of compression (crankcase, intake and/or exhaust).

Finally pressure test coolant system followed up by testing coolant for combustion gases.