Ignition gremlin
- Thread starter 50jeffrey
- Start date
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- 2023 CX-5 2.5 Turbo AWD Auto
RIP 8/23:2013 CX-5 Sport FWD Auto 120k
Carbon Cleaning and Diagnosis - Karmakanix VW & Audi Specialist Berkeley CA
Carbon Cleaning & Diagnosis for VW & Audi 2.0T. PCV issues and oil consumption are the real culprits. P0300 Misfire & P130A Cylinder Disabling
karmakanix.com
I’ve never done a compression test myself so I’d have to research how to perform it properly. Found some tips at the link above. Since the code doesn’t move to other cylinders when swapping coils that leaves injectors, PCV and valve seals as possibilities.
I never got a CEL but my ‘13 2.0L developed a slightly rough idle at just under 70k. I actually felt a couple misfires through the body that didn’t trigger a code but made me think yup, time to investigate. I cleaned the throttle body, swapped the spark plugs for new ones, and pulled the intake manifold to clean the carbon off the intake valves. It runs smooth and like new again. I’ve since done a CDC intake valve treatment and will keep doing so every 15k or so to stay on top of it.
hope you find the source, good luck!
Very understandable, and I've actually been in that situation myself in the past. All that's needed to keep a fluid conversation going is to mention that right away, because when there's no response, we don't know if you have no interest in what we write, or perhaps you're not seeing it, or whatever else the reason might be for not responding to the suggestion.
Yes, pulling the fuel pump relay is exactly the way to prep for the compression test. Then after it shuts down, vacuum and clean the area around the sparks, and remove all of them. Thread in the connector of the tool completely, and have a helper crank while you watch the gauge. While cranking, the gas pedal is pushed all the way to the floor, and it typically takes no more than 4-5 cranks to get to get max pressure on the gauge, so cranking should be stopped after 5 revs. Be sure to reset the tool back to zero PSI before testing the next cylinder.
Write down the results of each cylinder as you get them. After all cylinders have been tested, redo the test once more, and add a few squirts of your regular motor oil into the cylinder before doing the test. Write those numbers down as well, and then post back here with all of the results.
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- Plano, Texas, USA
Yes, that's true, and would always be done for a compression test anyway. But if fuel pressure isn't relieved, fuel will be spraying while the vehicle cranks during the test, which is the reason the fuel pump relay should be pulled and the vehicle run until it stalls.
I think you are pulling the relay for the low pressure electric pump in the tank. I think the high pressure pump is mechanical and always pumps. Starving the high pressure pump may introduce air which can be a big problem. I would rather evaporate a few ounces of gas than to risk getting air in the high pressure system and blowing stuff back into the injectors in the testing cylinder. It might clean the injector when it is spraying into a no pressure cylinder...
There is nothing at all mentioned about air in the CX-5 FSM, for the replacement procedure of any fuel system component. And there is most certainly trapped air in a portion of the fuel system, right after components are replaced.
So if Mazda doesn't provide any caution about trapped air being an issue, then IMO any air in the fuel system must be purged out via the injectors quickly enough so as not to cause any problems.
However, if someone is aware of any fuel system air problem, and can provide documentation of it, then by all means please post it here. Until that happens, I'll have no problem with pulling the pump relay, in order to relieve the fuel pressure.
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- '17 CX-5 Select
A go/no compression test can be done just by sound; roll the window down, floor the accelerator, press the brake and let the starter crank for a full 5 seconds. Record it and post here, if you want 2nd opinions.
If it sounds like this (uneven cranking), then maybe that's enough for you to take it to a mechanic, unless you're are an accomplished DIY and intend to the repair.
Verifying *which* cylinder is low (not necessarily the one that misses) requires a scope with external trigger or a two channel scope, plus (ideally) a DC reading amp clamp. You can use the battery *voltage* sags at each compression stroke to determine *relative* compression balance.
To acquire the absolute compression in PSI, you'll need a rental compression gauge, or an in cylinder pressure transducer, and any number of YouTube videos on how to do that procedure.
If it sounds like this (uneven cranking), then maybe that's enough for you to take it to a mechanic, unless you're are an accomplished DIY and intend to the repair.
Verifying *which* cylinder is low (not necessarily the one that misses) requires a scope with external trigger or a two channel scope, plus (ideally) a DC reading amp clamp. You can use the battery *voltage* sags at each compression stroke to determine *relative* compression balance.
To acquire the absolute compression in PSI, you'll need a rental compression gauge, or an in cylinder pressure transducer, and any number of YouTube videos on how to do that procedure.
I bought 2014 CX-5 Grand touring at 204000miles. Was good maintained one owner car. But has this P0301 code when I bought it. Code comes and goes as you have mentioned. Currently car has around 211000 miles. Drives perfect though.
Did you have any luck resolving this. My CX-5 has same exact issue. Changed plugs, coils at Dealership. Last diagnostic they did was to upgrade PCM programming, and decarb the valve ( I believe the rev up high few sec for couple of time). Code did not came back for about 1200 miles. But it is back again. (I might take it back for diagnostics) Always throw this code during morning at start. or initial slow speed. Never seen this happen when high speed or engine is hot.
Also notice that during the start in morning, engine rev up high for minute or so and revolution kind of uneven. But once rev settles it is very consistent. As I mention always happens during this start process. No issue in performance when driving.
