Hello all

My daughter bought a 01 s40 for a few hundred bucks. Upon initial inspection I knew it needed springs and an o2 sensor. No big deal, easy work. I replaced the springs up front, did the upstream o2 sensor. I had my brother in law pull codes for me and they were numerous. As of today, I have replaced the IAC valve/motor, MAP sensor, upstream O2, 2 new ignition coils, 2 new wires, 4 new plugs, new thermostat, new temp control sensor and a new fuel regulator,and a new battery. I cleaned the MAF sensor. At start up it runs well. As it gets to operating temperature idle starts to act up. In drive there is a lot of vibration (motor mount is next on the list after this idle problem), but still idles choppy. In reverse it seems ok, only ok. But better. In neutral or park it is also choppy and will stall out. So far I'm more into it for parts than my daughter spent on the car. I should note that it has 128k on the clock with a new timing belt and new turbo. Any help out there???

 

what codes present now? did you look for vacuum leaks - hoses, boots? Check the connectors to the coil packs to see if there's any cracks. Note there are two MAP sensors, and a throttle position sensor - but without codes and some other tests, its just guesswork. Have you measured fuel pressure?

 

These are the orginal codes from initial read

​​​​​​P0125 insufficient comment temp for closed loop fuel control
P0101 mass or vol air flow sensor "A" circuit range/performance
P0131 o2 sensor circuit low voltage bank 1 sensor 1
P0107 manifold absolute pressure/barometric pressure sensor circuit low
P0304 cyl 4 misfire
P0128 coolant thermostat (coolant temp below thermostat regulating temp)
P0301 cyl 1 misfire
Where's the other map sensor? I changed the one that's right at the front, smack in the middle above the radiator. I did not check the throttle position sensor (didn't think of it) and I did not do a fuel pressure test. What is the correct pressure supposed to be? I can get my hands on a pressure tester
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Since it starts acting up once it warms up, I would suspect a faulty coolant temperature sensor. If it thinks the engine is still cold as it warms up, it wil tell the computer to dump more fuel than a warm motor needs, causing an over rich condition. Can you pull the codes now that you have changed a lot of parts and see what you still are working with?

 

I don't know where my last post went, soooo.... Anyway

I did check vac lines, though some could use replacement, they don't seem to be bad enough to cause a problem. I did not do a fuel pressure test, but I can. What is the correct pressure supposed to be? Also, where is the second Map sensor? I changed the one front and center, above the radiator area. The codes I got originally were

P0125 insufficient coolant temp for closed loop fuel control
P0101 mass or vol air flow sensor "A" circuit range/performance
P0131 o2 sensor circuit low voltage voltage bank 1 sensor 1
P0107 manifold absolute pressure /barometric pressure sensor circuit low
P0304 cyl 4 misfire
P0128 coolant thermostat (coolant temp below thermostat regulating temp)
P0301 cyl 1 misfire

 

One of the codes that has been constantly there is the MAP sensor one. I'll have to pull the codes again to see what was exactly what. I do remember whittling codes down to p0107 and 0101. As for 0107 the only thing I haven't changed is the MAF sensor, but I cleaned it. Now that I know they're are TWO map sensors, I can go after the other one. Hey, the upside is she'll have all new sensors, so there's that....

 

Cylinder misfires may be from hairline cracks in spark plug leads. Very common to fail at higher mileage. I’m told you can try for sealcwith silicone first to see if that makes a difference. I have not done this, just replaced mine and problem sent away. Hopefully someone who has can chime in. I would also be very tempted to replace all vacuum lines in sight. Will save you headaches later and it’s a quick and easy job.

 

Every time I have tried to clean a MAF sensor, it has never solved the issue or actually made it worse. Might want to consider just replacing it if you still get a code for the MAF

 

My take is on the MAF being faulty as well.You can clean it and it might will run better but once it actually throws a code it is bad and should be replaced as a 1st step..On the PH2 the manifold pressure sensor is actually on the manifold just under the fuel rail.It looks the same as the one you already changed on the IC.Dirty fuel filter also could wreck havoc worth to check it out.Dirt/water in the gas tank clogged injectors as well.
For the misfire you have the 1-4 cylinder on the same coil so thats kinda tells me that the coil itself needs to be replaced or you have a lose connector feeding it which is a very common problem on this car..
New thermostat also need to be installed to get rid of coolant related codes.

 

And just to throw some more confusion into the mix, I once had a Coolant Temp Sensor from the generic auto parts store that was bad right out of the box. A genuine Volvo CTS fixed that issue.

Also, check the 1" hose that connects the IC to the throttle body. It's an S shaped hose that gets brittle and cracks in half. This will cause idle issues if broken.