2006 Volvo S60R surging problem
 

Hello,

I have a 2006 Volvo S60R. It has 136000 miles on it and runs great, with the exception of a recurring very minor surge that occurs when cruising at constant speed. Usually 25 - 35 mph or so. It is barely noticeable. However after doing this twice, it displays a check engine light with the code P0101. I have had it into the Volvo dealer several times for this issue. They did a smoke test for leaks on the turbo piping and replaced a section. Same problem re-occurs. I replaced the EVAP canister and associated hoses twice, initially cleaned the original throttle body, then replaced the throttle body. Replaced the MAF. It has recent new coils and plugs. New stock air filter. All hoses and fittings are tight and in good condition. All parts are factory Volvo parts. No aftermarket. It has been doing this for about 1-1/2 years now. I have just about given up. If anyone has any suggestions I would really appreciate it.

Thanks,

Mike

did you use a genuine Volvo MAF? some years are sensitive to after market parts, even from Bosch et al. Have you looked at your fuel pressure? Also the ECT sensor?

Yes, it is a Volvo MAF as well as throttle body. I have not checked the fuel pressure and am not sure how. It is the original engine coolant temp sensor. I will change that.

in about 2005 volvo went to a variable pressure pump which has a fuel pressure sensor and a pump control module to manage the pump. Not sure about your model but check to see if there's a shrader valve (like a tire...) on the end of the fuel rail under a cap where you can hook up a gauge.

Yes, my car has the Schrader valve. I will put a gauge on it. What should it be reading at idle? I just ordered the ECT sensor. Thanks for the help by the way. I appreciate it..

not sure of the exact spec for idle but here is a good discussion since the pressure will vary

https://www.matthewsvolvosite.com/fo...d%20flush%20it.

Thanks. I checked the fuel pressure with a diagnostic tool I borrowed. The fuel pressure is reading right around 58 psi. The tool also recorded a fault in the ECU. The car has the IPD software upgrade so I am not sure if that is what is causing that. Given I have replaced just about everything I just purchased a used ECU to try.

Update: I replaced the ECU with a reprogrammed unit using XeModex. The car ran perfect for about 10 miles. Then started its usual subtle stumble and recorded P0101 and P0442 codes. Same old problem.