2001 S80 Erratic Idle and Knocking

BeardedEagle · Post by **BeardedEagle** » 07 Dec 2013, 10:18

I have a 2001 Volvo s80 2.9L non-turbo 77,xxx miles. It will run fine until it gets up to temperature. When it gets warm, the idle ranges from 200 rpm to 1500 rpm and will stall at times. I have replaced the ETM, PCV system, spark plugs, and ABS module (all with Volvo parts) and have traced all wires and vacuum lines for failures to no avail

. It has had a slight knocking that has gotten worse over the last month (sounds like "put put put" kind of like exhaust leak or air pump leak) but I am not ruling out the fact that it is a mechanical knock because I cannot hear it well enough. The knock seems to be coming from the #1 cylinder side of the motor either in the front of the motor (crank pulley side) or near the firewall. I am about to give up on the car and hope that I can get my money out of it. Any suggestions would be greatly appreciated.

Post by **Oly_850** » 08 Dec 2013, 19:44

Have you tried chasing the a potential vacuum leak around the intake manifold? Use carb cleaner and spray around the mating surface while the car is idling. You might also try ( carefully ) cleaning the MAF sensor, or disconnect it to see if you get an improved idle. Are you getting any codes?

BeardedEagle · Post by **BeardedEagle** » 10 Dec 2013, 19:26

Thank you for the response.

The check engine light is not illuminated and my Actron scan tool does not show any codes. Is it worth it to go to a Volvo mechanic and pay the $90 for them to scan the car for error codes, or is my basic scan tool going to tell me what I need to know?

I know the actual light on the dash worked three weeks ago. I had an ABS wheel speed sensor wire that had a bad splice. Looks like the dealership tried to cover up a boo boo they made when replacing the timing belt.

The motor's timing is good, by the way.

I sprayed starting fluid near all vacuum connections that I could find and there was no surge in the idle. I disconnected a vacuum line and sprayed the fluid directly into the intake manifold and there was still no surge in its idle, which I found to be odd. What is your thought on that?

I had already carefully cleaned the MAF and that did not change anything. I disconnected the MAF while it was warm and running and it stalled immediately. I reconnected it and it started fine. I shut it off, disconnected the MAF and it started and ran fine for about ten seconds, the idle became rough and erratic. It stalled after about 20 seconds. There was no check engine light. I reconnected the MAF and started the car and it acted like it did when I had the MAF disconnected, would run rough and stall after about 20 seconds of running. After it stalled, the electric radiator fan was running with the key out of the ignition. I started it again, it stalled and the fan was still running. (I have no reason to believe that there was a logical reason for the fan to be on. Maybe it is the car telling me what is wrong with it in its native Volvo tongue) Still, there was no check engine light. I repeated this a few times and decided I should run home and grab my scanner, and a beer to calm my nerves, to see if I could detect and clear any codes that could be preventing the car from running even though I had reconnected the MAF and there was no check engine light. I disconnected the battery to disable the fan while I was gone. I came back after about 20 minutes with my scanner. Before I did anything... well after I reconnected the negative battery cable, I tried to start the car and, with great relief, it started fine. I assumed the battery being disconnected cleared whatever it was that was making it think that the MAF was disconnected. The scanner showed no codes.

Then, I went home and cried myself to sleep because I still have no idea what the problem is.

MyS40T4 · Post by **MyS40T4** » 11 Dec 2013, 16:36

I had a similar problem with a s40 t4 - it turned out to be a faulty temperature sender that failed when it got up to operating temperature. If the S80 is the same (the sender is used for the temp gauge and fuel injection for engine temp.) then this could cause the issue. Easiest way to test is to disconnect it and run the car until up to operating temp. yes, you'll get a code but the car should behave when fully warmed up. Or measure resistance when cold and then when the problem starts measure resistance again.

homeagain · Post by **homeagain** » 11 Dec 2013, 17:47

I trust when you installed the ETM you had it done where software was also installed.

BeardedEagle · Post by **BeardedEagle** » 12 Dec 2013, 14:58

Hey, Mys40t4 are you talking about the coolant temperature sensor?

Yes, I have the proper software installed on all components.

Thank you all for chiming in!

MyS40T4 · Post by **MyS40T4** » 12 Dec 2013, 15:52

Hello, yes the coolant temperature sensor - in my case the car was fine until it got up to operating temperature. Then the sensor's resistance implied a sub-zero engine temperature

and it ran like a dog after that!