engine misfired when it is hot?

Question

I have a VOLVO 1994 850 w/250000 mile, sometime it misfired when it is hot

Answer 1

zef 66 is correct check for basic ign. tune up items first then inspect coil you will see small white burn spots on the black plastic body the coil is replaced with the ignitor as a assembly and the dealers seem to keep a large supply in stock.
Note more frequent tune ups prolong the coil life by reducing secondary resistance and thus the peak firing voltage[electricity is lazy] it takes the path of least resistance weather its a burnt plug wire or a worn plug or through the side of the coil.

Answer 2

Yes, this can be a problem, espically when it is hot. I would suggest a tune up if your vehicle is doing this on a regular basis. First things would be to change the spark plugs and wires. If they are fairly new, then check to make sure they are gapped correctly. You should have the plugs gapped to the reccomendation under the hood of the car. If the problem still persists, I would try changing the coils out next.

If the engine misfires only once in a long time, I wouldn't worry about it. If it doesn't do it that much, it won't hurt a thing.

Answer 3

Does it misfire and stall or just stumble?Is your check engine light on?
Check temp sensor located on the thermostat housing also check throttle body for crud buildup look for vaccum leaks and check the cap and rotor.
If you need any further assistance contact me i spend 60 hours a week working on Volvos.