Signs of a Blown Head Gasket
- Thread starter murdoc_47
- Start date
Well, it was a fun run, but I might be at the end of this project. I got everything buttoned up today and started her up for the first time. Well, I cranked it a while with the fuel pump disabled first to build some oil pressure. Then I started it up. After a bunch of initial racket and rough running, the engine smoothed out and settled down. Happy to say I have no leaks, VERY unhappy to say that I do have errors. First I got a P0031, but found that I hadn't fully seated the O2 sensor, so I plugged it in fully. But my heart really dropped when I saw I also have a P0017 error which indicates timing is off, and I still show a P0304, which is what started me down this path.
I REALLY don't want to pull the front cover off again! I swear I checked the timing chain MULTIPLE times and all of the marks were lined up right with the case, and the marked links in the chain. I even took pictures to prove it to myself. I wonder if the VVT isn't working right. Anyone know how to test the VVT?
I'm also not sure if the P0304 was left in the ECU from before I started this project? (fingers crossed) The only thing left that could cause the miss-fires is just a worn out cylinder and rings. And I just don't think I have it in me to pull this engine and do the whole thing top to bottom. For what it would cost, I'd be better off getting a used engine with a warranty for around $2000.
If I could get the timing sorted,
Feeling pretty defeated...
I REALLY don't want to pull the front cover off again! I swear I checked the timing chain MULTIPLE times and all of the marks were lined up right with the case, and the marked links in the chain. I even took pictures to prove it to myself. I wonder if the VVT isn't working right. Anyone know how to test the VVT?
I'm also not sure if the P0304 was left in the ECU from before I started this project? (fingers crossed) The only thing left that could cause the miss-fires is just a worn out cylinder and rings. And I just don't think I have it in me to pull this engine and do the whole thing top to bottom. For what it would cost, I'd be better off getting a used engine with a warranty for around $2000.
If I could get the timing sorted,
Feeling pretty defeated...
- :
- 2023 CX-5 2.5 Turbo AWD Auto
RIP 8/23:2013 CX-5 Sport FWD Auto 120k
Im far from an expert on anything like this (so don’t fire her back up on my advice alone), but I found a report on timing being off being thrown due to low oil 2016.5 CX-5 2.5L Timing chain skipped a tooth?
Anybody think the first start after rebuild and without fuel pump on could’ve caused the code? Like, clear the codes and give it another whirl now that oil has circulated in the system and there’s now fuel pressure? VVT wasn’t happy on first start?
Anybody think the first start after rebuild and without fuel pump on could’ve caused the code? Like, clear the codes and give it another whirl now that oil has circulated in the system and there’s now fuel pressure? VVT wasn’t happy on first start?
AL Cx5
2024 CX-5 Prem Turbo Tuned Lowered Forged Wheels
I'm sure you cleared the codes and tried it again by now. I wouldn't be overly concerned on the initial start up and maybe you didn't clear the codes before you started the project.
To build oil pressure on new engines we prime the oil pump before spinning the motor. We remove the spark plugs as well. I've removed an engine plug and used a garden type sprayer to force oil into the oil pump. Some guys pack the oil pump with assembly oil to prime the pump. After the time and expense to build an engine, we want it to make oil pressure as quickly as possible.
IF it throws a code on the next, brief, start up, then be concerned.
Good LUCK!!
To build oil pressure on new engines we prime the oil pump before spinning the motor. We remove the spark plugs as well. I've removed an engine plug and used a garden type sprayer to force oil into the oil pump. Some guys pack the oil pump with assembly oil to prime the pump. After the time and expense to build an engine, we want it to make oil pressure as quickly as possible.
IF it throws a code on the next, brief, start up, then be concerned.
Good LUCK!!
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- :
- Plano, Texas, USA
I’m lazy and just Googled “P0017 code Mazda CX-5” and here’s the result from its “AI Overview”:
”The P0017 code on a Mazda CX-5 means the crankshaft and exhaust camshaft (Bank 1 Sensor B) aren't synchronized, often due to low/dirty oil, a faulty oil control valve (OCV) solenoid, a stretched timing chain, or bad VVT components, causing poor performance, rattling noises, and potential engine damage, requiring checks of oil level/quality first, then VVT parts or sensors, and potentially timing chain inspection.”
So if you’re sure you’ve lined up everything correctly while installing the timing chain, your leaky OCV could be the culprit?
So I'm following up on this story just in case anyone finds it in the future. I put this project on hold for several months. It was just too cold out during the winter to work on it. Finally got back around to it this past week. I took the timing chain back off and removed the cams. Then inspected the HLA's VERY closely and found several of them were bad. (Could still compress them after bleeding them in an oil bath) So that was what was making all the racket when I started the car up in the fall. I found a cheap set of HLAs and rocker arms off of ebay and installed them this week. And I VERY carefully re-installed the timing chain making sure it all lined up perfectly. When I was done I started up the engine and the clatter was gone, just a LOT of ticking sounds like a sewing machine. After I drove it a bit it quieted down significantly.
It's not perfect, still a little louder than I want, but there's no check engine light, and the car is driving. Now I have to figure out why the AC decided the quit working, but that's a different thread entirely.
The last thing I did to the engine to try and help it was put a can of "Restore" in it to try and restore some of it's lost compression on cylinders 3 and 4. I'm not willing to sink more money in the engine with 314k miles. So I hope this helps. Otherwise it's going to get driven around town until it dies. I'll do a compression test today or tomorrow to see if the magic ooze did its magic.
It's not perfect, still a little louder than I want, but there's no check engine light, and the car is driving. Now I have to figure out why the AC decided the quit working, but that's a different thread entirely.
The last thing I did to the engine to try and help it was put a can of "Restore" in it to try and restore some of it's lost compression on cylinders 3 and 4. I'm not willing to sink more money in the engine with 314k miles. So I hope this helps. Otherwise it's going to get driven around town until it dies. I'll do a compression test today or tomorrow to see if the magic ooze did its magic.
Lazy2.5
2015 Mazda 6 - AT - Tuned
- :
- Ontario
I believe there is a certain amount of mileage that needs to be covered for those additives to take full effect. you may want to hold off on the compression test.
Liqui Moly also has a different type of "stop leak" additive specifically for conditioning worn seals that you can try using next oil change. cheap way to potentially further increase compression.
I've actually already driven the car about 50 miles. Today at lunch I ran the car for couple minutes while I hooked up my code scanner and then performed a compression test. So here's the good news, either all of my repairs have worked, or the magic goo worked. Now I have ~150 PSI compression across all cylinders.
Here's the bad news, I'm still getting cylinder 4 misfires. The cylinder isn't completely dead, just shows a handful of misfires every polling cycle. Enough to light up the dashboard and set the PO304 code.
Now I'm REALLY at a loss. Here's everything I've done to try to fix this specific problem:
Can anyone think of anything else that would trigger misfires ONLY on cylinder 4 that I've overlooked?
I might finally throw in the towel and take it to the dealer for diagnostics. But that feels like admitting defeat! lol
Here's the bad news, I'm still getting cylinder 4 misfires. The cylinder isn't completely dead, just shows a handful of misfires every polling cycle. Enough to light up the dashboard and set the PO304 code.
Now I'm REALLY at a loss. Here's everything I've done to try to fix this specific problem:
- Replaced Coil, Plugs, and fuel injector
- Swapped plug and coil with other working cylinders
- Had Cylinder head professionally rebuilt. All Valves done, camshafts checked.
Can anyone think of anything else that would trigger misfires ONLY on cylinder 4 that I've overlooked?
I might finally throw in the towel and take it to the dealer for diagnostics. But that feels like admitting defeat! lol
Lazy2.5
2015 Mazda 6 - AT - Tuned
- :
- Ontario
Yes, but you want to make sure it stays reasonably high.
As for cylinder 4, wiring also came to mind. Not sure. Keep us updated.
Maybe a defective spark plug? That happened with me. All 4 were causing misfires.
Interesting. Can you elaborate? What does the heat gun do that the regular temperature of the engine bay not do? and would it be pointed at the coil? With the intake in place you can't access the injector.
Or do you mean one of those laser temperature guns? I know the cylinder is firing some times. It's just also detecting misfires, and the plug is darker than the others.
Forgive me for not reading the whole thread from beginning but were the coils , plugs and injectors OEM? If coils aren't, have you swapped #4 coil with other cylinder that's not misfiring.
Coils, plugs and injector have all been replaced and swapped on #4
Yeah, it took me a minute but I figured out what you meant. Thanks, but that's nearly impossible to remove the heat shield that is on top of the exhaust manifold and get a heat gun in there accurately with everything in place. I'll consider it, but I'm fairly confident that the cylinder is firing, just misfiring.
- :
- 2023 CX-5 2.5 Turbo AWD Auto
RIP 8/23:2013 CX-5 Sport FWD Auto 120k
I gave Gemini a shot (for better or worse). I dont think 1 Intake deposits is credible based on how much inspection you have performed so far. Check out 2, wire harness integrity is interesting. Not sure if 3 is relevant to line 4s the way it discusses a bank, suggestion over my head tbh. I like the vacuum leak test but I don’t think you’d get good compression if that was the issue? Grounding and battery would be an easy fix if the culprit, doubt that would cause a single cylinder issue though.
Gemini:
That is a frustrating diagnostic puzzle, especially after seeing healthy compression numbers across the board. Since your friend has already addressed the "Big Three" (Spark, Fuel, and Compression) for Cylinder 4, the issue likely lies in a subtle mechanical timing variance, a localized sensor fault, or an intermittent electrical break.
Here are a few specific areas to investigate that would cause a rhythmic misfire on a single cylinder:
1. Carbon Buoyancy or Intake Valve Deposits
Even with a rebuilt head, if the intake manifold was not thoroughly cleaned, carbon deposits can break loose or restrict airflow specifically at the Cylinder 4 runner. On GDI (Gasoline Direct Injection) engines like the SkyActiv-G, airflow turbulence is critical. If the "magic goo" mentioned was a combustion chamber cleaner, it’s possible some loosened carbon is intermittently fouling the spray pattern or valve seating.
2. The "Pulse" Test: Wiring Harness Integrity
Since the coil and plug were swapped with no change, the focus should shift to the Cylinder 4 Fuel Injector Harness and the Ignition Coil Connector.
• The Problem: Heat-cycling can cause the plastic connectors or the pins inside to become brittle or loose. A "handful of misfires" suggests a vibration-induced or intermittent connection.
• The Fix: Perform a "wiggle test" on the wiring harness while the engine is idling and the scanner is polling. If the misfire count jumps, you’ve found a break in the wire or a backed-out pin.
3. Crankshaft Position Sensor (CKP) vs. Cam Sensor
While a failing Cam Position Sensor usually affects the entire bank, the Crankshaft Position Sensor is what the ECM uses to detect misfires by measuring minute fluctuations in crankshaft speed.
• If there is a slight nick or debris on the reluctor ring corresponding to the Cylinder 4 stroke, the ECM might "see" a misfire that isn't actually happening (a ghost misfire).
• Check for any debris near the CKP sensor or damage to the tone wheel.
4. Vacuum Leaks (Localized)
A leak at the intake manifold gasket specifically at the Cylinder 4 port will lean out that cylinder.
• Diagnostic Tip: Spray a small amount of intake cleaner or use a smoke machine around the Cylinder 4 intake runner. If the RPM stumbles or the fuel trims shift, there is an unmetered air leak bypassing the MAF for that specific cylinder.
5. Grounding Issues
Modern Mazdas are sensitive to grounding. There are often ground lugs located on the cylinder head or near the strut towers. If the ground for the ignition harness is slightly oxidized or wasn't torqued properly after the head rebuild, it can cause "noisy" signals that manifest as intermittent misfires.
6. Low Voltage / Battery Health
It sounds unrelated, but SkyActiv engines behave erratically when the battery is marginally failing. If the voltage drops during the injector firing sequence, Cylinder 4 (often the end of the fuel rail or harness) might be the first to show symptoms.
Summary Checklist for your friend:
1. Wiggle Test: Check the injector and coil connectors for Cylinder 4.
2. Vacuum Test: Check for leaks at the manifold runner for Cylinder 4.
3. Relative Compression (Electronic): If the scanner allows, run a relative compression test to see if the ECM sees the same 150 PSI "work" being done as the manual gauge.
4. CKP Inspection: Ensure the crank sensor is clean and the mounting bracket is tight.
Does he have access to a bi-directional scanner that can look at "Fuel Trim by Cylinder" or "Ion Sensors" data?
Gemini:
That is a frustrating diagnostic puzzle, especially after seeing healthy compression numbers across the board. Since your friend has already addressed the "Big Three" (Spark, Fuel, and Compression) for Cylinder 4, the issue likely lies in a subtle mechanical timing variance, a localized sensor fault, or an intermittent electrical break.
Here are a few specific areas to investigate that would cause a rhythmic misfire on a single cylinder:
1. Carbon Buoyancy or Intake Valve Deposits
Even with a rebuilt head, if the intake manifold was not thoroughly cleaned, carbon deposits can break loose or restrict airflow specifically at the Cylinder 4 runner. On GDI (Gasoline Direct Injection) engines like the SkyActiv-G, airflow turbulence is critical. If the "magic goo" mentioned was a combustion chamber cleaner, it’s possible some loosened carbon is intermittently fouling the spray pattern or valve seating.
2. The "Pulse" Test: Wiring Harness Integrity
Since the coil and plug were swapped with no change, the focus should shift to the Cylinder 4 Fuel Injector Harness and the Ignition Coil Connector.
• The Problem: Heat-cycling can cause the plastic connectors or the pins inside to become brittle or loose. A "handful of misfires" suggests a vibration-induced or intermittent connection.
• The Fix: Perform a "wiggle test" on the wiring harness while the engine is idling and the scanner is polling. If the misfire count jumps, you’ve found a break in the wire or a backed-out pin.
3. Crankshaft Position Sensor (CKP) vs. Cam Sensor
While a failing Cam Position Sensor usually affects the entire bank, the Crankshaft Position Sensor is what the ECM uses to detect misfires by measuring minute fluctuations in crankshaft speed.
• If there is a slight nick or debris on the reluctor ring corresponding to the Cylinder 4 stroke, the ECM might "see" a misfire that isn't actually happening (a ghost misfire).
• Check for any debris near the CKP sensor or damage to the tone wheel.
4. Vacuum Leaks (Localized)
A leak at the intake manifold gasket specifically at the Cylinder 4 port will lean out that cylinder.
• Diagnostic Tip: Spray a small amount of intake cleaner or use a smoke machine around the Cylinder 4 intake runner. If the RPM stumbles or the fuel trims shift, there is an unmetered air leak bypassing the MAF for that specific cylinder.
5. Grounding Issues
Modern Mazdas are sensitive to grounding. There are often ground lugs located on the cylinder head or near the strut towers. If the ground for the ignition harness is slightly oxidized or wasn't torqued properly after the head rebuild, it can cause "noisy" signals that manifest as intermittent misfires.
6. Low Voltage / Battery Health
It sounds unrelated, but SkyActiv engines behave erratically when the battery is marginally failing. If the voltage drops during the injector firing sequence, Cylinder 4 (often the end of the fuel rail or harness) might be the first to show symptoms.
Summary Checklist for your friend:
1. Wiggle Test: Check the injector and coil connectors for Cylinder 4.
2. Vacuum Test: Check for leaks at the manifold runner for Cylinder 4.
3. Relative Compression (Electronic): If the scanner allows, run a relative compression test to see if the ECM sees the same 150 PSI "work" being done as the manual gauge.
4. CKP Inspection: Ensure the crank sensor is clean and the mounting bracket is tight.
Does he have access to a bi-directional scanner that can look at "Fuel Trim by Cylinder" or "Ion Sensors" data?
