98 S70 popping on startup

Camaro737 · Post by **Camaro737** » 07 Feb 2023, 14:48

I just replaced injectors after one was stuck and caused a hydrolock on start up. No damage caused compression checked and each cylinder reading 150psi. Oil was also changed and a new mobil 1 filter went in. When I drive there is no noise at all, even idling after starting sounds normal. It sounds like a slight popping not really a metal on metal noise and sometimes it doesn't even happen. I have no idea what it is, doesn't really sound like a lifter but then again I haven't been around volvos long enough to know any tell tale signs of issues with my car. Thanks

WhatAmIDoing · Post by **WhatAmIDoing** » 07 Feb 2023, 16:04

Is the popping coming from the exhaust or the engine? A connecting rod can be bent while still showing compression. Did you disconnect the battery to reset the ECU and perform a relearn?

Camaro737 · Post by **Camaro737** » 07 Feb 2023, 16:21

I didn't disconnect the battery, could that stop the noise? It sounds like it's coming from the driver's side of the engine more towards the firewall if anything. The cylinder that got flooded was the furthest one on the passenger side. The black cover over the distributor cap also has a crack in it could that be causing it? I don't know too much but I would think that a bend rod would cause some noise especially when flooring it?

Post by **abscate** » 07 Feb 2023, 16:36

If it’s the black plastic cap over the red ceramic cover not really important. If it’s the actual distributor cap it needs to be replaced, pronto.

Flooring an old car is a quick way to turn it into a parts car unless you Stage 0 it first.

Camaro737 · Post by **Camaro737** » 07 Feb 2023, 16:42

It's the black cover. I only got on it after I have driven about 100 good miles with no issues. Other than that noise when starting it its driving like its brand new. The noise doesn't sound like metal at all, what comes to my mind every time I hear it is like air being pushed through, could air still be making its way through the fuel rail? Because I also replaced my fuel filter and all the lines were pretty much drained. I have no check engine lights and my scanner says all my systems are good I don't know how reliable that is though.

Post by **scot850** » 07 Feb 2023, 16:48

Can you record it an post for us. That may help us get a better idea. At the moment I would be just throwing guesses out there.

Neil.

Camaro737 · Post by **Camaro737** » 07 Feb 2023, 17:33

Here's the video. That hum just started too, I let it sit with the battery disconnected to reset it so that may be why that noise happened?

Post by **scot850** » 07 Feb 2023, 22:39

It could be a bearing is noisy in the timing belt area or the serpentine belt. Removing the serpentine belt and starting the engine for a short time when cold will eliminate the items that are connected by the serpentine belt. then remove the timing belt cover and listen again to the components there.

Neil.

Camaro737 · Post by **Camaro737** » 08 Feb 2023, 05:48

When I started it this morning it did the pop again but nothing else. I decided to turn on the AC and it kept kicking on and off while making a similar noise, I'll record and post a video when I get home, I think your on to something! Thanks

Camaro737 · Post by **Camaro737** » 08 Feb 2023, 12:29

Ok so on my way home it was rough idling again like it was before I did the injectors. I wanted to see if any smoke was coming out of the dipstick, (worst case scenario I broke a ring) and there was a decent amount coming out, I did Robert's glove test and it was all fully warmed up, as I opened the cap oil started to spill out like crazy and the glove did inflate so the PCV system is clearly broken! I just don't know if any of the rings can still be bad though?