I have a 1998 volvo s70 with a 2.4 non turbo and i have replaced the wires coil sparkplugs the head gasket and i am still geting misfire codes for all cylinders and it has the IAC code up to and random cylinder misfire code at a idel the cars rpms keep going up and down and the hole car shakes but after you start driving it then it runs fine untel you are at a stop light it runs bad agin untell you start driving agin i realy need some help with this car i am due to have my first son july 31st and i want to make sure i have a good running car so we are not broke down on the side of the road what could the problem be

 

RANDOM misfires are usually caused by fuel system/ air intake issues, as opposed to problems with the ignition system More specifically, if the car is running lean, it will cause random misses. Make sure all the vacuum lines are in good condition. Check the mass air flow sensor (MAF) - try disconnecting it, then starting the car and seeing if it improves. If it does, you MAY need a new MAF. Try cleaning it first, they sell a special cleaner specifically for mass air flow sensors at the auto parts store. if cleaning it doesn't help, look for vacuum leaks- either vacuum lines, or around the intake manifold. The idle air control (IAC) valve could also be failing- this is a common problem. There's ways to check all of these problems, so don't just throw parts at it- IAC valves and MAF sensors are expensive parts.

Also, if you try disconnecting the MAF, a code for it will be set, so erase codes before continuing with diagnosis- don't assume the appearance of a code means that a particular part is bad.

 

I agree. Vacuum leak.

 

All the hoses are good cant find out were the leak would be if there is one this realy sucks

 

try the other suggestions in my post.

To look for vacuum leaks around the intake manifold gasket, spray some sort of non- flammable liquid around the intake manifold where it bolts to the head, while the engine is running. If the engine "picks up" or smooths out, you found your leak.

 

Mine runs perfect, but throws codes, Cyl 2 misfire, Multi cyl misfire etc
Can not feel any miss/
Car ran great, put new plugs and wires. no codes, then changed the air filter and the coil wire, started throwing codes, mostly misfire codes, bought another coil wire still throws codes, I replaced the MAF about two years ago, could it be bad again?
THANKS
Robert

 

Did you replace the MAF with an OEM one? If not I hear the generic ones don't last long. Also pull the MAF out and spray some MAF cleaner on it. I put mine on some newspaper and gave it a good cleaning and I haven't had a problem with it yet.

 

Check the hose on the bottom side of the air control valve. A loose hose there caused our rough idle problem.