Hello! Novice backyard mechanic with an automatic 1984 Volvo 240 making rattle/ping noise under load. I've looked up what I could find and watched a lot of videos, and don't believe I've heard the exact condition elsewhere. It's a low mi. car (~84,000 miles). It starts/runs/drives well but I think this noise has been happening intermittently under load since I've had it running (maybe 4,000 miles). Usually not present, but always appears at some point while driving/accelerating. Noise happens especially when stepping hard on gas usually between 2-4k rpm, stops if you let off slightly, or becomes more jangly at the higher rpms. Cannot produce the sound in park even revving. But, I made a video by revving in drive with brakes on and it made a similar rattle. Honest, compared to this video, the sound is usually less pronounced under driving conditions (and more rattly, less consistent).

Anyway, please give a listen? Sound starts around 0:26. Pre-detonation? Knock? Ping? Slap? Help! Thanks in advance



Extra info: I inherited the car and got it running by fixing badly retarded timing, replacing fuel pump(s) and reversing direction of a vacuum check valve that wasn't right. Valves are a bit out of spec a bit on 2 cylinders (too much clearance). I have the hushers for the valves but haven't installed because I'm afraid to go too deep!

Here's a list of what else I've done in case it helps/rules anything out:
-FPR new
-New timing belt, dist cap, timing is +10-12 (in spec).
-Both fuel pumps replaced, new fuel filter.
-New other belts
-O2 sensor replaced
-New gaskets on TB, Exhaust manifold
-New exhaust (not Cat)
-Cleaned throttle body, intake
-New transmission filter/oil
-Coolant flushed/new
-Fresh oil
-New flame trap
-lots of other little stuff... (knock sensor works, checked electrical in many places)

 

Does not sound good sounds like a bearing. What kind of oil are you running in that car 10w30 when's the last time you changed it

 

That is pinging - preignition/spark knock due to over advanced timing/low octane fuel. Check the timing when it's making that noise (you will have to trust the person pushing the gas pedal!) I'd bet you will find it off the scale.

I Don't remember what a 84 had for the ignition control unit. Is that the one with a vacuum advance on the control unit itself? Or on the distributor?

 

Thanks. The 84 has the advance on the control itself. The timing is in spec at idle, but even retarding it to like 4 I still get the spark knock under load (same dangerous test with no helper and in D with parking brake and me rotating the pulley). I don't really know what I'm doing but seems like I should check the RPM/timing chart and see, which means I can't use my 11 year old on the gas pedal, haha. Next stop. I broke a stud on my exhaust manifold trying to see if it was a leak, so now I'm doing lots of stuff (new mounts) maybe pulling the head- which is over my head!

 

Yeah it's changed often and is 10w30.

 

Hi, I think I might have a very similar issue on my car.

Just checking if you managed to resolve this?

 

Yes. There was a Volvo brand check valve (white/black) on the vacuum line when I bought the car that I assumed was normal. It wasn’t supposed to be there I found out after posting elsewhere. So, I think what was going on was the timing was too advanced because after the first time I hit the gas the controller had high vacuum constantly. I removed it and the adjusted the timing to +12 and all good after that. There was another check valve on the fuel pressure regulator line that I also removed. This is all specific to my ‘84 and whoever was fiddling with it before I bought it- so not sure it will help, but, good luck

 

What's the max spark advance you see when reving?