S40 missing under acceleration

jtz54 · Post by **jtz54** » 22 Nov 2009, 11:48

I have a 2002 Volvo S40 with 135K miles. Until recently the engine has been great with an average of 30MPG. The last month or so under full throttle, the car has started missing and sometimes the check engine light is blinking but no codes are stored. In the last week it has gotten worse and sometimes starting from a signal, the car just sits there for 3 or 4 seconds (similar to a carb loading up) before it wants to move. I thought the fuel filter was clogged so I changed it. Seems to run a little better from start but the WOT problem is still there. When I was leaving the gas station a couple of codes came up on my Scan Gauge P171-System Too Lean and P237 Boost Sensor A circuit Low. Has anyone had experience dealing with similar problems. BTW I had put in a new set of plugs and wires about a week ago but this didn't change anything. Could this be related to the infamous Volvo ETM problem?). Not sure if the 2002 S40 was affected because I haven't seen it on the recall list.
Any help appreciated.

jtz54 · Post by **jtz54** » 24 Nov 2009, 12:57

Been reading in other forums that the P0237 code usually means a bad MAP sensor. Going to try replacing that along with the boost controller. Will report back when it is replaced.

Post by **OEMVolvoParts** » 11 Dec 2009, 15:29

The map sensor is up there with the number one predictable problems on your car. The new plugs, wires, and coils is my next best guess as to what is causing the mis-fire. Since there has been no update, did the map sensor fix it?

jtz54 · Post by **jtz54** » 12 Dec 2009, 10:15

The MAP sensor and coil on #3 cylinder was bad. When I replaced the MAP sensor it got rid of the rough idle and low speed problems. Still had missing under WOT. Replaced the plugs but no help. Replaced the coils and now it's all good!

Post by **billofdurham** » 12 Dec 2009, 11:41

Thank you for the update.

Bill.