Hello!

My name is Andrew. I have lurked upon these forums various times recently and in the past for issues with my Volvo's. I most recently purchased a 2001 S40. I was aware at the time of purchase that the exhaust system (specifically catalytic converter) codes were coming up. As the deal was too good to pass up, and my father and I concluded that it was worth the purchase compared to dealer prices, we took it upon ourselves to start repairs after purchase. As my dad is knowledged and experienced in car maintenance and repairs, and I am a sponge when it comes to learning things, we figured the general catalytic converter issue was something we could address ourselves.

The beginning of the journey was to take both old ones off, and put the new aftermarket parts on. After doing so we noticed some difference in engine running, but still have significant issues with engine sluggishness and acceleration hesitation. The engine at idle though runs a lot smoother and we are under the impression that the engine is not the issue. So I ventured to my nearest Autozone, and asked for an OBDII check. From this I got back 4 codes:

P0420
P0301
P0303
P0102

These are in order of which the codes were read out from the scanner. We have checked all 4 spark plugs and both ignition coils and we believe that due to their relative little wear, they are relatively new. As well research has shown to me that the Fuel Pressure Regulator on this model is a genearl issue, and so we simply replaced the part from NAPA. Is there any way though that they may be bad? As well I have read that the MAF code could be addressed as a MAF sensor issue. In some of the posts people have said they simply disconnected the MAF sensor, and saw a change in engine run. We have not. The other main cause the code has said was a Vacuum leak. This is something more of an issue that I nor my father are not 100% sure how to look. Finally, as I believe 3 of the 4 codes seem to point to bad O2 sensors, what is the possibility of those actually going bad?

I apologize if my post seems too detailed (or not enough), and I as well hope my relative newness as a member does not cause issues to the fact I have posted so soon!

Thank you for any help!


Andrew

 

These cars are well known for the P0420 code unfortunately. I used a Cel Boss from IPD to permanently rid myself of that issue. Did you replace the bottom O2 sensor when you replaced the cat convertor? Did you erase the old trouble code? Do you live in a state with emissions testing? (Cel Boss - Oxygen Sensor Spacer (CEL Boss) IPD 109553 3C1151 )

When you wrote "We have not" did you mean "we have not seen a change in engine performance when we disconnected the MAF"? or did you mean "we have not disconnected the MAF"? If you have done the test and there is no change then suspect the coils. If you have not done the test then, well, do the test!

About those coils. They will ohm good and still be bad sometimes. How? Hairline cracks in the plastic part the sits down into the spark plug well. These hairline cracks allow spark to jump to the head instead of travel to the spark plug (path of least resistance is the head). You cannot see the sparks because the top part of the coil blocks your view. Inspect the coils with a magnifying glass. In every misfire case I've had on my 2001 it was always the coils or wires. Now I have read where a person used JB Weld to coat the plastic to cover the hairline cracks and stop the arcing. Never tried that myself as I purchased new coils. Could have saved me some cash.

To check the fuel pressure regulator go get a cheap Harbor Freight fuel pressure tester. The shrader valve is under the plastic cover for the fuel rail. The call it a "fuel injection pump tester" Fuel Pressure Tester & Fuel Injection Pump Tester

And since all modern cars use OBD-II, I would highly recommend a code reader. Again, Harbor Freight has several models to choose from. Get a CAN BUS compliant unit. No more trips to the auto parts store to use their reader. (And my local store won't erase the codes!)

Let us know what you find?