My colvo 850 is running a little rough in low revs almost like a slights stutter but nothign corse if that makes sense its more like a wobble in the low revs from about 1500 to 2500 beyond that runs perfectly fine. i have replaced the fuel pump and the red fuel relay near the fuse box. please help was wondering if it may be a crank angle sensor or a camshaft pos sensor

 

Simple test. Have you checked all of your vacuum lines?

 

I have note how would i check those?

 

Is it a turbo or NA? What year?

 

Na, 1996

 

Check Robert DIY videos. He has one for every Volvo issue

. -

 

start by inspecting the hoses by the vaccuum tree under the throttle cable spooler cover. you can google for a vacuum diagram to see where they should go. Make sure the branches without hoses have caps on them - note if you have a PCV problem the positive pressure can pop those off. Do a glove test to see if your PCV is properly venting (see RobertDIY's Youtube vids on the how to. If you don't find anything, you may need to do a smoke test since there are obscure places where the vacuum lines go. Next is look at the date code on the spark plug wires. If they are over 5 years, time to do a full stage 0 tune up - OEM plugs (copper old schools work better than newer iridium/platinum etc), cables, rotor, cap. Note you can do this without removing the intake airbox but its much easier getting at the distributor cap if you pop that off first. You can also spray around with carb cleaner to see if you have any cracks in the intake air hoses and your injectors.

 

Thank you guys for all your help I'll be checking all of these tonight

 

I'm going to say it's not possible for sensors to cause that problem, unless it was the MAF, which I don't think any of us would suggest.. If you a vacuum leak, then at higher revs the leak gets smaller as the MAF measurement gets bigger, and so it improves. however, you may have a dead miss. They definitely smooth out at higher speeds. FWIW. The miss would be the typical stuff. Under load at the same rpm, a vacuum leak will improve a lot. Under load at the same rpm, a dead miss will get a lot more ugly.

 

How do you repair a dead miss?