Volvo S40 Rough Idle/Misfire/Electrical Issues
 

My 2002 Volvo S40 is experiencing many issues and has only worsened with the winter season. Not trying to type a story here, but many of these issues have spanned over the course of a few months. When I first purchased the car, in July, I noticed the AC would change power and temp on its own. The man I bought it from told that the computer sensors (I believe) were dying and just needed to be replaced. No big deal. Never got around to it, but didn't cause me too many issues. A few weeks later, CEL comes on and reads PO128. Guy told me easy fix, explained it to me, told me if I brought it to the dealership they could take care of it. A few months pass by, and the car runs smoothly. I took it on a trip to Virginia, an eight hour drive, and noticed the car jerked just slightly upon any kind of acceleration, but didn't think much of it either. Later on in that trip, I noticed the Up Arrow/Transmission icon flicker just slightly. In the manual, just stated transmission but didn't raise much alarm about it.

A few weeks later, I was starting the car and pulling out of the parking lot. (I remember being low on gas, almost to gas light range) Suddenly, the car just quits, and my wheel locks up hard as does my brake. Gas pedal is limp. Radio and electrics still work. The Transmission icon, CEL, battery, and a few other dash icons come on as well. Restart car, works just fine. Scared the hell out of me. Took it in for an oil change, they said everything looked fine in it. It happened a few more times and I decided to do some investigating. I read the codes from the car, here goes: PO172, PO101, PO139, PO130, PO301, PO302, PO303, PO304, PO128. Reset all of them, and after only a small amount of driving, PO172 and PO139 come back on. PO128 does as well, when you run the AC. So I assume the rest are related to the misfire. Have tried to do a lot of research, because I know a dealership would take all my money. It seems like MAF may be a common denominator. I did get a good look at it however, and no real visible damage or dirt. I do know there is still the possibility of it still being dirty. Air filter is clean and fluids seem to be fine as well.

I wanted to explain how the car runs. When it's cold, typically, as soon as you start it up after sitting it will do the misfire thing reported above. It's become so casual as it's happened so many times with me pulling out of the drive way or other places. Just a restart and it's gone. Some things I have noticed though, about the way it runs:
-It seems like you have to rev it to fight off the misfire/shutdown. But, if you do, when you begin to drive, it jerks and drives very rough. Like, strangely.
-It struggles to start sometimes and you have to turn the ignition for a solid 7-10 seconds on occasion.
-Electric issues do seem to be present though, with windows and stated AC/radio computer issues.
-Car just doesn't seem to run smoothly sometimes. Struggles with acceleration on occasion and getting up to speed, will lag and then jump up to speed quickly.
-Idles very rough. Sits at a constant RPM of 1000-1300. This evening I could hear it reving on its own, and there was a noise coming from the engine after deceleration on the rev. (Either huffing or some kind of fan scraping?) I attached a picture with the location marked because I could almost pinpoint the spot.
https://cimg0.ibsrv.net/gimg/volvofo...ad267829a3.jpg

-Gas mileage doesn't seem to be very good either. I go through a full tank is 2,3, or maybe 4 days and that's with a 35-40 mile day AT MOST.

There are just so many issues with this car and I have no idea where to start. I could really use the advice because I'm not in a position to go spending money guessing on the issues. Thank you so much for reading this all and for your time.

the P0172 code is telling you there's a fuel trim issue. MAF sensor can do that, as can a routine vacuum line leak, so the first step would be to inspect for torn hoses, cracked intake air boots etc. try spraying around with some carb cleaner if nothing is obvious. P0139 is a slow o2 sensor response code... usually this means the downstream O2 sensor is reporting a gap vs the front sensor - could be a cat issue - particularly if the car has been running rich for a while or if the cat is not working efficiently or the sensor is bad. The P0128 code is reporting the engine is not getting up to temp. This could be due to the thermostat or the ECT sensor (Most people simply replace both as you need to remove the thermostat cover and top hose to get at the ECT sensor). Rest of the codes are misfire codes - probably caused by the fuel trim being off. So my plan would be 1) check for vacuum leaks 2) replace the ECT and thermostat ($75 in parts, 30 minute DIY job - 15 for the ratchet, 15 to figure out how the wiring socket unclips) 3) check you battery system voltage - engine off, engine on, engine on with full load (lights, blower motor, rear defogger etc) and clean/retighten terminals 4) see if any bad behavior persists. Tough to chase down electrical connectivity issues, but these steps can help eliminate some of the easy fix items.

I'v been just having similar symptoms the last couple of months.I had a bad/dying fuel pump.After did replace it some jerking still remained misfire and whatnot.What I figured I had water in my tank.When I replace the pump I did look for dirt didnt look for water.At this point I had a choice to make.I either take the pump out again and dry the tank fully or try to add some additives first.Had about a 1/4 full tank so I added a full bottle of Red Heet and run the car until I was down to about a gallon left.Car felt good the jerking was gone.Next refill I added another bottle and been happy ever since.Depending on the amount of water you might get away with it too.I had a quart of 92% rubbing alcohol ready too if Heet didn't do the trick.