Popping from manifold after PCV change

adbalt · Post by **adbalt** » 07 Dec 2015, 03:37

I recently changed the PCV on my 98 Volvo S70 GLT. After getting it back together and starting it up it runs worst than before. Irratic idle, occasional popping sound from within manifold, thick white smoke exhausted with what appears oil. Does anyone have any idea what may have caused this before I start to take it apart again? Thanks for the help.

Post by **rspi** » 07 Dec 2015, 07:31

Post by **RussB** » 07 Dec 2015, 07:36

Did it run OK before you installed the new PCV system?

Post by **jblackburn** » 07 Dec 2015, 07:38

Check to make sure you didn't pinch the bracket on the bottom-right screw between the IM and engine. Common mistake, creates a huge leak, and makes the car run terribly.

Post by **erikv11** » 07 Dec 2015, 11:21

What jblackburn said, check that the manifold is sealed all the way around, starting with the bracket at #5 cylinder.

adbalt · Post by **adbalt** » 07 Dec 2015, 17:40

Thanks for the help. The car ran fine prior to me replacing the PCV. I'm new to working on cars and am trying to learn. So that occasional popping noise I'm hearing is caused by the manifold not being sealed properly? I checked the bracket and it was not between the the manifold and the engine. Would you all recommend I loosen the manifold bolts and try to retighten? And would a bad seal around the manifold cause the pressure to remain, fail the "glove test" on the oil cap, after the oil trap was replaced? Thanks again.

Post by **jblackburn** » 07 Dec 2015, 20:01

I would check to make sure it is reseated firmly against the gasket. The lower screws need only be loosened - the manifold slots in on top of them, and then the top ones are inserted. Tighten sort of like you would wheels - top left, bottom right, top right, bottom left, then hit the ones in the middle.

Check your air hose @ the throttle body to make sure it hasn't popped off at the bottom - that happens to me all too frequently after doing a bit of work on it.

Also while re-seating the intake manifold double-check that you have the top two hoses to the oil trap routed to the correct places as shown in our PCV tutorial; I have seen diagrams that mix those two hoses up before, and it will cause the car to inhale oil instead of creating vacuum in the right place in the box.

adbalt · Post by **adbalt** » 08 Dec 2015, 12:12

Thanks. I rechecked the oil trap and hose below the throttle body and they were good. I bought a new manifold gasket just to be on the safe side. While taking the manifold off I saw the large hose coming from the top of the turbo had become unclamped. Im sure that was causing some of my troubles too. The bright side is I got pretty good at taking the manifol off. Do you happen to know what the popping noise, almost like popcorn, was coming from? Vacuum leak cause that? Thanks for your help.

Post by **jblackburn** » 08 Dec 2015, 13:02

A backfire I guess, possibly from it running too rich from the wrong A/F mixture (hose being off).

Did you happen to remove the distributor leads? I've mixed those up before - found a wrong picture of the order of the wires on some forum. Here is the correct order:

Is it still running badly, or haven't got it all back together yet?

adbalt · Post by **adbalt** » 08 Dec 2015, 16:29

I'm waiting on a manifold gasket tomorrow. I figured while I had the manifold off again I better be safe than sorry in case there was an issue with it. I'm going to tighten the bolts the way you advised and see if that makes a better seal. Any specific pressure per bolt necessary? Before I took it off again this afternoon I tightened a few manifold bolts and it helped dramatically. The exhaust was pretty clear and it stopped spitting oil, so I think you got me on the right track. Still popped occasionally but a lot better. I'm hoping a better seal and the turbo hose connected solves the issue. Also, is there a better way to put on/off that lower manifold bolt (one with the clip). Tough to get to and I'm afraid of stripping it. Thanks JB.