Hey guys! I recently picked up another 2001 s40 after totaling my other. When I bought the car it had 5 codes, ebay listing only showed 1 (p0420) I cleared the codes and drove it for 150 miles and re-scanned them. Came back green, no pending codes and car ran pretty good. Car was sitting for 3 months prior to me buying it. I drove it for another 100 miles and the P0420 cat code came back. Sometimes under hard acceleration (pedal to floor) the car kinda jerks and surges while accelerating could that be due to a clogged cat or something?

The original codes when I was at the dealer were:

P0420

Thermostat temp P0128

Misfire in cylinder 2

Coil bank 2 circuit

P0455

I have driven the car for over 300 miles and the only code that came back was the P0420 sometimes the car has great power and sometimes she does not.

Any help or suggestions would greatly appreciated.

 

not sure about the cat issues but the most common root cause for the misfires is usually bad coil packs. There are two which each feed 2 sparkplugs. Assuming of course that you've already checked the plugs of course.

 

The P0420 is telling you the cat is not operating at proper efficiency - usually that means its heating up too slowly. That can be caused by exhaust leaks or crud in the cat. Certainly running an extended time with a misfire can cause some build up of crud. What I'd do is fix up the misfire - could be the plugs, could be the coil packs or could be the wiring connectors to the coils. Second, I'd consider replacing the temp sensor - its the one right under the thermostat dome - just follow the upper radiator hose to the block. A good time to replace the thermostat as well. Finally, you can try cleaning out the cat by running some extra detergents in your fuel tank and by switching to 93 octane for the next few tankfuls. Clear the code and see if it returns.

 

Sweet thanks for the input, I just bought new Volvo plugs, coils and spark plugs. I also bought a new thermostat, fuel filter, air filter, and a Bosch downstream 02 sensor. Hopefully this will clear up the problems. I normally run 89 octane and put Lucas system cleaner every 2000-3000 miles but since I just purchased this car I have no idea how the person took care of it.

 

there are some videos on Youtube that have ways to clean a cat without removing it.


Also, My S40 had similar crazy issues with idle overrun. I changed a lot of stuff related to vacuum leaks, etc.... but the big one, and it is easy to do yourself is the Electronic Temp Sensor. It is inside the T-stat housing. Folks go ahead and change the T-stat and gasket with it. And I had the best results buying VOLVO brand everything. Don't mess around with Chinese sensors. But I have been 3 months and no codes, no erratic idle.


If you have a Volvo computer you will see that the sensor is telling the ECU that the car is -47 and it should load up with fuel....


another thing I did was buy a Ox Sensor Boss. It pulls the 2nd sensor out of the exhaust flow so it either does a better job reading, or does not read at all.... only about $20 vs buying a new O2 sensor and the codes go away.

 

So far I have acquired all the parts mentioned, the car hasn't done the shaking or surging part when I put it in drive but I noticed recently that it's been clunking pretty hard when I put it from P to N or R to D. Also when coasting it starts to slow down significantly but no true signs of the dreaded hard shift. I did notice on the highway the other day, when I went to accelerate about 50% it just revved up then it caught the gear and started to accelerate.

My question is now, before I go ahead and put $700 worth of new parts on the car or put new transmission fluid in it do you think its worth it with said issues about the transmission?

 

Well the optimist in me says change the fluid and see what you find out. I definitely would not be throwing any other parts at it first though. Good luck I hope it works out.