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98 S70 throwing p0304 code

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

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Year and Model: 1998 S70
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98 S70 throwing p0304 code

Post by pdillard » Fri Apr 21, 2017 9:55 pm

I bought a 98 S70 base model (non-turbo) automatic with 156k on it about 2 weeks ago. It seems to run fine. Since the service records end at 77k I took it to Meineke for an oil change and they looked it over, said everything looked good but they recommended a fuel injector cleaning since the mileage is so high, and it looks like they could be dirty, from the outside anyway...I looked under the injector cover and yeah its kinda dirty in there, but for a car with this many miles it should be a lot dirtier. I passed on the cleaning.

About a week ago the CEL came on, no flashing, just solid. I took it to Autozone and the codes were P0303 and P0304. I thought maybe it was the fuel injectors. I put a bottle of Liqui Moly in it and the light went off 2 days later. The light came back on today, again no flashing, just solid. I took it back to Autozone and the code read P0304 and P0300 (random misfire). So i'm thinking the problem is cylinder 4 and that is causing the other codes.

The car doesn't spit or sputter or show any symptoms, though I have noticed when I'm stopped at a light or sign there is a slight bump/jump every few seconds, but nothing major. It's barely noticeable.

I got under the hood today. The spark plugs and wires look fine, probably replaced in the last few years, as well as the ignition coil. I took out the #1 and 4 spark plugs and compared them to a used spark plug chart and they looked what can be considered good. I can hear the injectors ticking. Overall it sounds and looks smooth and quiet. No smells either, and no loss of fluids or leaks of any kind, though there were a few spots of oil under the spark plug cover, which I read can be normal on a higher miles volvo. I sopped them up and I'll check back on them in a few hundred miles.

I'm not really sure what could be causing the misfire. I'm not the best mechanic. I can handle tune ups, replacing alternators, that sort of thing. But the inner workings of the drivetrain are over my head.

Anyone know what the issue could be? Maybe I should have had the injector cleaning done?

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Re: 98 S70 throwing p0304 code

Post by kahl » Sat Apr 22, 2017 6:37 am

I would eliminate injectors from being the problem at this time. Without knowing how long the spark plugs have being in service I would change them out with the Volvo spark plug. I would bet your misfire code will go away.

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