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Discussion Starter · #1 ·
Ok so I've had my 2001 V70 na for about 4 months now and after a few days i get an ecm3502 code also shows on regular scanners as p0301 misfire cylinder one plugs are newer and have swapped out multiple coil packs car runs fine idles fine. I do notice one thing after i turn it off though sounds like a soft popping sound in the intake only does it once every time i shut the car off like 5 seconds or so after turning it off. Is this a possible ETM issue?
 

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That's a misfire on cylinder 1. Check the plugs, coils, injectors... and do a compression test. ETM making a noise after shutdown is normal.
 

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Discussion Starter · #3 ·
I have already swapped out a few coils and it still returns, Have already checked the plugs and injectors all in good shape. Am gonna do a comp test this weekend and maybe swap out a few more coils and check the plugs again to be sure. It usually takes a few days to a week to return. The DTC usually only sets in the morning after the car has been off for the night. This last time there was no code when the car was shut off the night before and in the morning the DTC is thrown as soon as it starts.
 

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Things you can do.

Compression test both cold and hot.
Swap injectors.
Check for vacuum leaks by smoking the system. I'd do it on a cold engine and make sure it's sealed (MAF capped) to allow some pressure to build within the intake, not more than a couple psi. Possibly a leak at the intake manifold gasket.

Can the code reader read LTFT and STFT?
 

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Discussion Starter · #6 ·
Coil wiring is fine. Finally did a cold compression test which are #1 90psi #2 180psi #3 200 psi #4 180 psi #5 200 psi. #1 is a bit low... Car did sit for 2 years sticky lifters perhaps? It doesnt burn any oil. Am going to do a warm compression test tomorrow.
 

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Discussion Starter · #7 ·
Maybe a leaky injector putting too much gas in the cylinder washing the walls perhaps?
 

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Back in the 70's working as a mechanic at a Porsche-Audi dealer, the Audi Fox would have valve troubles. By putting each cylinder with the piston all the way up and the valves closed (as if it was firing) then put 100 psi into the cylinder. We used a Snap On tester that regulated in 100 psi in, then another gauge showed the leak down.
If you did that to your bad cylinder and it showed leakage........a noise in the exhaust pipe would say...exhaust valve. A noise while opening the throttle would say...intake valve. And a noise coming out of the oil cap ....might say rings. The Audi never seemed to have bad head gaskets, but maybe a bad head gasket might bubble up the coolant, if bad enough.
Those cars had solid lifters, and with the valve cover off, it was easy to do this test. Without doing a leak down, your only guessing.
I'm sure it might more difficult to do on a Volvo, but if your leaking past a valve, maybe that's your problem.
I don't remember everything from back then, but with 100psi in, and the other gauge showing 20 psi would equal a 20% leak. I think that's how it worked. Maybe its a lesser pressure going in, but its a percentage of loss your looking for. And doing it this way points more to a specific problem area.
 

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do a wet compression test.

drop a tablespoon of motor oil into the cylinder, roll it over twice and then do your compression test.
If the numbers come up substantially it's rings. If they stay down it's valves.
 
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