Hi, I bought a 99 S70 non turbo a few mo ago, after buying it I did my normal fluid changes and replaced what might have been the original spark plugs (their was not much left). Ran OK, but quickly starting loosing power and sputtering when passing and going up hills, Iv replaced some of the vacc lines and the fuel filter and cleaned the throttle body with maybe a slight improvement. Yesterday I tossed in some lucus fuel cleaner and drove about 50 miles and got a check engine light! Code po420! Doubt this could be causeing the car to run poorly, but what happened? Could have the cleaner triggered the code? Any ideas on what could be causing my power loss?


Thanks;
Chad

 

Something is interfering with the burn process and you're throwing a cat. code. With your history I would suspect other issues first (but that could be because I don't want to change out the converter!) If the plugs were really old so were the wires, cap, and rotor. Did you get the right plugs with the right gap.(Volvo plugs come pre-gapped and are- in my experience - right on). How's the air filter?
Don't know what you used but some people have reported problems after using Seafoam to clean stuff out, I have thrown O2 codes on 2 different cars with the stuff.

Start at the vacuum "tree" at the right front of the engine and go back over the vac lines , including the tree itself, might be cracked.

 

Hi, thanks for the reply. Their air filter is new, plugs are "Bosh" as recommended by the parts store, their is no wires or cap, I have the coil on plug set up and everything was in good shape and dry down by the plugs. I did find a vacc leak going to the heater door on the air box and repaired it with no change, changed some of the lines to the map sensor and so on since they looked questionable, pulled the throttle body off and cleaned it with no change what so ever. Seams to run better now that I ran fuel injector cleaner trough it, but that's now when the CE light came on.

 

Huuuuuuuummmmmmmmm. When accelerating you are putting a demand on the engine to do several things, more fuel, control air, adjust timing, etc. The computer has to make a lot of fast changes to help the car preform well under load. One of the big things is spark, thus people usually suspect that plugs are worn or bad, which your's were. Volvo engineers played special attention to this a designed a plug to work good in these cars. When someone else recommends another plug for the car, are they making a better decission than the team of experts that are trying their best to design a car to run so well that they will have their jobs 5-10 years later, probably not. So, even though Bosh plugs are world class, they my not be the BEST choice here. Even if Volvo had Bosh make plugs for your car, the Bosh versions of the matching plugs may be a little different.

Besides that, most owners of these Non Turbo I5's do not know that the NA motors actually have a higher compression ratio than their turbo'd brother. The NA motors have a 10.5:1 compression ratio while the turbo motor has 8.5:1 ratio. What this really means is that it makes it MORE important in the NA cars to run 91+ octane fuel than in the turbo cars. By LAW (I was told it was a law but have been unable to verify this), all cars have to be able to function on 87 octane fuel, this supposenly went in effect in the late '70's (I actually think it was only required in about 8 states). Since cars cross state lines all the time, auto manufacturers make their cars meet the requirements for all of the cars they sold in the US. (That is also the reason that most cars sold will meet the CA emission requirements). Anyway, car companies that make cars to operate and function on 91+ octane had to design a system for the car to run on lower octane fuel, most will run on 87 octane. So if you look in your owners manual it will say that the recommended octane fuel rating is 91+ but the minimun is 87 octane. The system they designed and installed in these cars is the KNOCK SENSOR system. If your car senses that the fuel octane is low, it will have the computer adjust the car's preformance to compensate for lower octane fuel and retard the timing to avoid KNOCK. KNOCK is when the fuel in the chamber explodes under pressure (usually premature) instead of by the spark as designed by the computer system.

All type all that to say this, if you are running fuel with lower octane than 91, you are likely causing your car to adjust preformance to avoid KNOCK. So, if you are running 87 octane and have more than a 1/2 tank of gas, toss some octane boost in the tank and drive the car a while to see if it helps. The next 2 tanks of gas make sure you pump 91+ octane and see if that cures your problem.

Please don't start the discussion that it ran fine 5 years ago or your friends car runs just fine on 87, all things being perfect/new/fresh the car would likely run well on 87. However, for some reason your car is 10+ years old and worn to the point that it doesn't like it anymore. There is a chance that you have a bad knock sensor and there is a chance that you have a bad catalytic converter. I really don't know but I would start at the 91 octane fuel.

Make sure your plugs are gapped at .028. Yes they should have been gapped but maybe there were not correctly gapped.