Rough idle even after new PCV
 

Hey guys

So after recently doing a valve cover gasket change on my 1998 318ti (M44 engine), my car threw a check engine light code for P1174. After doing some research on the forums, I read that a bad PCV or CCVV could lead to this. I took off my oil cap and felt positive pressure coming out so that led me to confirm the PCV must have went bad. I just changed it out 30 minutes ago but once starting the car, the car idles rougher and still has positive pressure coming out of the valve cover. My revs do not bounce around but i can feel the engine rocking slightly back and forth. Any ideas? I'm just really stumped and frustrated at the back to back problems and would like some help from the forum.

Vacumm leak?

Did you replace the hose of the pcv?

I didn't change the hose, I admit I didn't want to pay $25 for a new oem hose. Should a general emission hose work just fine?

There is a cheap oem replacement by rein

Buy that instead

Do you have a link to said hose? I can't seem to find it.

I recommend to do smoke test for the vacuum leak, here a DIY for the smoke machine. http://www.pontiacbonnevilleclub.com...opic35820.html

About the idle issue, try to clean the ICV (Idle Control Valve). Watch video.

https://www.youtube.com/watch?v=lhIM4bsjOaY

If CCV is new and hose doesn't leak (If leaking it can be replaced with cheap heater hose) you have a piston ring blow-by issue if excessive combustion gas if blowing out your oil fill hole. Do a compression test or even better a Leak-Down test will tell you everything about valves and ring blow-by.

Sorry to break the bad news but if there is combustion gas coming out the oil hole with a new CCV valve on there it is a mechanical issue (rings, piston worn so bad it is slapping side to side)

John S

Thanks for the help guys. I wont be able to work on the car till later this weekend but I appreciate the replies. Going to try and clean the ICV and change out the hose. Then going to see if a friend can do the compression test for me/check for vacuum leak.

@xxxJohnBoyxxx I really hope its not that but if it is, RIP :(

If you got a lot of miles try the Seafoam internal cleaning. That stuff will break/remove all the junk in the combustion system. Some oils have wax in them and other stuff that will gum up the rings and cause your blow-by issue.

ICV would never cause positive crankcase pressure only gasses getting by the piston rings

Alright thanks John, I'll give it a shot. After driving last night I realized there was a noticeable drop in power in my engine. Not a major drop in power but I definitely remember there being more torque in first gear with the pedal to the ground.

This is a sign of worn mechanical parts and most likely you have a cylinder low on compression. Do the compression test to ensure you don't have a problem with rings or cylinder wall

John S

Alright, its been a while but some updates. Car got smoked tested and there's quite a a lot of vacuum leaks. Planning on getting the hoses changed out, given that the car has 175,000 miles. Will update as it comes along!