CYLINDERS 3 & 4
1998 VOLVO S70 OLD SPARK PLUGS LOOKED WET AND SMELLED LIKE GASOLINE. IF INJECTORS ARE LEAKING; COULD THE ENGINE STILL RUN SMOOTHLY ABOVE 2000 RPMS?
Yes. I would try a can of sea foam with a full tank of gas. This should clear that up for you.
I added a can of sea foam; but only with 5 gallons of gasoline. I ran the engine 1 1/2 hours and it runs much smoother than before. It has little or no misfiring above 1000 rpms; but idles roughly at 1000 rpms. After that, I now have a new code, P0172. My code reader says "system too rich". What causes this code and what can I do to correct this problem?
http://www.obd-codes.com/p0172 -- check this out. Could still be an injector issue or maf needing to be cleaned. This link has some helpful solutions
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