PLEASE HELP! Even the dealer can't diagnose it!

Post by **drvolvo** » 03 Aug 2009, 21:57

I have a 2001 S40 with 141K on it.

Ok, so it all started with a rough idle in park followed by a check engine light. The CEL was for the heated oxygen sensor which was replaced. At this time I also noticed that when the car was in gear but stopped at a light, the engine RPMs would sometimes suddenly fall (or slip down) and the car would shudder briefly and it would feel like the AC compressor kicked on (but the AC wasn't on). The car never stalled but it felt like if the RPMs went any lower it would have. After the Heated oxygen sensor was replaced and within 30 minutes of having the car back the check engine light came on again. This time the code said it was the Mass Airflow sensor that needed to be replaced. So that was replaced and yet again the check engine light came on for the Mass Airflow sensor and a misfire code. At this point the shop I took the car to replaced the new Mass Airflow sensor with my old sensor and told me to go to the dealer.

After a day at the Volvo dealer I am told my booster sensor (solenoid valve) needs to be replaced. Again, 30 minutes or so after having the car back, the check engine light comes on. This time, not only does the car drop RPMs briefly while stopped at a red light, it also does a new thing. Before going to the dealer, if I put my foot on the brake and then revved the car up to 2000RPMs, the car would smoothly return to an RMP level below 1000.

After having the solenoid valve replaced and feeling the same drop at a red light I took the car into a parking lot to rev the car to 2000RPMs. This time the car well overshoots the 800-900RPM mark (falling to 400 -600 and erratically bouncing around before going back up to the sub1000 mark) and the car nearly feels like it is going to stall.

I am calling the dealer back tomorrow to inform them of this new development, but they said they didn't have many ideas if this sensor replacement didn't solve my problem.

So, any ideas guys and gals? I'm desperate on this one. I am trying to move to Maryland from Rhode Island and I can't get out of Dodge! (Plus I wonder if it is safe to drive the car in this condition. It only does this issue at low RPMs but its still concerning since no one knows what the root cause it. )

ANY HELP IS GREATLY APPRECIATED!!!!

Post by **drvolvo** » 07 Aug 2009, 16:06

In case any one is curious, it took the dealer two days to figure out that is was the rear (and not the more common front) booster sensor (solenoid valve) that was causing all my trouble.

Happy Day!

Post by **uhlan** » 17 Aug 2009, 15:40

Have a similar issue. can you tell me roughly where these front and back sensors are located?

drsugg · Post by **drsugg** » 17 Aug 2009, 18:28

You should check the vacuum hose going to the fuel pressure regulator. Pull the hose off and see if there is any sign of fuel in the hose or the pressure regulator. Any fuel is too much. Saw this last month and car had similar symptoms.

andrewearle · Post by **andrewearle** » 18 Aug 2009, 22:42

These were the exact symptoms I had with my ETM. I have a '00 V70, these were known for their sub-par ETM, but I'm not sure of the S40's. A cleaning will help, but the whole throttle may need replacing.

My car's RPMs dropped below idle when coming to a stop (around 500-600), and the car shook like it was going to stall. If I was was in park and revved the engine up to 3000 or so, the RPMs would overshoot, and either stall or be on the verge of stalling.

Luckily I was under the extended warranty (10 yr./200k) and the dealership replaced the throttle body with no expense to me. This took some hand pulling. I took the shop forman for a ride in my car, and he personally worked on it. Ultimately, it worked out. I'm not sure if the S40's suffer from the same crappy ETM, but this sounds exactly like what my car was doing.

Hope this helps

P.S. AWESOME SITE!

mjsparky363 · Post by **mjsparky363** » 23 Aug 2009, 05:15

It may be too late but my daughters 03 had exactly the same problems and after similar "dealer maintanence" to the tune of 650.00 it turned out to be a battery enven though the car had no symptoms of a weak or bad battery. Good luck.

ikeo31 · Post by **ikeo31** » 24 Aug 2009, 06:48

i have a 93 940 turbo wagon with 86,000 miles thats been doing that a couple of years.the dealer and other garages cannot find the cause.