Crank, stalling and revving problems - air coolant sensor?

[scottkr]

Hi all,

I have a 2001 S40 that recently started have trouble with cranking, proceeded by problems with ramping to 1,500 - 2,000 rpms at an idle, and then several revving instances while driving. Initially problems with revving occurred only when the car was not warm, but the more I drove the problems persisted when car was warmed up. I took it to the shop and the news was bad: codes read that I needed a new MAF, crank, cam and air coolant temperature sensors. It all put me at about $1,000 for parts + labor. Being that my car is not worth $1000 investment (ie will not get that back upon trade in), I decided to 1. buy several of the parts on my own (the shop suggested this as an option), and 2. replace the easy sensors.

Fast forward, the MAF and crankshaft have been replaced, problems persist, but now the car is cranking terribly. I basically drain the battery trying to get it to start, and when it starts it is in a fuel-rich stage -- ie at 2,000 rpms when idling. Also, temperature gauge at first reads at the hottest, then drops to coolest within a minute. I towed it back to the shop, and now the only code that is reading is the air coolant temperature sensor. The mechanic mentioned that there are problems when not buying replacement parts from the volvo dealer, but that this may be an overall problem with my computer.

So - could the air coolant temperature sensor be what is responsible for the bad running conditions/cranking? And, is it possible that the parts I purchased are somehow not showing up as error codes but still not fully functional?

Recognizing that the likely answer to these questions are "no", any other thoughts on what the issue could be?

[alschnertz]

I'd start with basics.
How many miles are on this car? Has it been maintained?
Has anyone changed anything? Is all the original wiring in place and not compromised by other mechanics or "tuners"?

Are the spark plugs good? Are they the proper type and gapped correctly?

Are the coils and spark plug wires in good condition?

Have you checked all the vacuum hoses? Are any cracked and dried out? Do they fit tight onto their respective fittings?

Clean the MAF (Mass Air Flow sensor), IAC (Idle Air Controler) and TB (throttle body).

Check the fuel pressure. Should be around 44 psi.

Has the fuel filter ever been changed?

Do all the basic things before you start throwing parts at it.

[difflock54]

Aside of checking the fuel pressure is at the correct 44psi check the IAT (intake air temp' sensor.)
If that is the problem it would explain the very rich fuel mixture you say you smell when it eventually struggles to cope with when it finally starts up.