I bought this 07 s40 from someone who said the timing belt had jumped teeth. He was right, it jumped a tooth but that has been taken care of with new belts and tensioner. Not sure how I didn’t notice until I fixed the timing and started the car that the catalytic converter had been removed. I don’t have a lift so I was never under the car. So there is that but I straight piped it temporarily to be able to start the car without neighbors calling the cops. Further inspection leads me to believe that the car was in a pretty good accident impacting head on. I think that is what made the timing jump but it has been very generically repaired. None the less, everything works after couple hours of bending and pulling and wrenching on hoses and brackets all right behind the radiator. Power steering and ac hoses. So once all these things were “fixed” I started the car and the engine sounds strong although still loud exhaust. One sensor was still in place just before the cat but the other was just hanging wires. Obviously I would get check engine and codes for the sensor low voltage. The car would run for 15-30 seconds then die. After that initial start it will only run for maybe 1 second before killing. So I got another sensor for the missing one.. but I don’t have a new cat.. so I just left the sensor hang there for diagnostic reasons. Which led me nowhere because for one, I’m sure you can tell by now, I am not a mechanic. And 2, I have same symptoms. I had a bunch of credit at a local junk yard so I replaced all the vacuum lines, and vacuum pump. Same symptoms.. I noticed the car would run at idle forever without stalling if I unplug wire connector to the throttle body. So I replaced the That and all related sensors. One at a time with same end result. Engine starts then dies. I was about to start playing with the timing but I was messing with the intake hoses and wires and noticed if the wire harness was plugged into the throttle, but the vacuum hose just after it is not connected .. the car will run and even drive. There is some obvious misfiring going on which is sure is because of the vacuum line not hooked up and air and gas and everything is off.. but I replaced the plugs and coil packs all with original Volvo stamped parts. The code I get for the misfire is just the p0300 random multi cylinder misfire. Replacing the coil packs and plugs did no good though. So in short, the engine won’t run longer than a second unless that vacuum line is not connected. In which case it runs.. like ****. I also have thoroughly cleaned and tested the injectors. Oil and filter change, replaced the purge valve thing. Air temp sensor, oil pressure sensor which I had those 3 parts already from a 2008 S40. No change in the outcome though. Only code I get is random misfire.. so my questions are. Should the car run without either sensor for the catalytic converter? Should it run with one sensor installed properly and the second just freeballing? And last but not least, if it is the timing causing the engine to die right away, would it run without that vacuum hose ? I’m about to go play with the timing. Please someone stop me if you have a better idea. Thank you in advance. Any and all comments are welcome because I am stumped

 

If the cat is missing, are you also missing the front O2 sensor? Did you try unplugging the MAF to see if that changes anything? What codes do you get when you scan the OBD2? Check for missing vacuum lines or torn boots etc?

 

The front sensor is still there and the back sensor is just connected to the wire clip but not installed anywhere. There are no vacuum leaks but if I create one, it will keep running. Mass air flow sensor I also replaced with no change. Fuel pressure is also good too which is why I haven’t touched the fuel pump.. which if the engine runs with or without that vacuum hose, the fuel pump must be working, right?