New member. Knocking engine between 2.5K-3.5K rpm

[99_VX]

Hello All,

I just got a 99 VX . The previous owner was supposedly using Mobile1 10W40. When I got the car I switched to Mobile 1 5W30. Anyways I was hearing a slight knock from the engine when I got it. So I decided to put Seafoam in the crack and intake. After putting the seafoam the knock sounds slightly louder. I do not hear a knock on idle but do from 2.5K to 3.5K rpm or so. I also believe the knock gets louder on load (driving it in 1st gear for example). I cleaned the EGR valve when I changed my oil not sure if it is leaking. I have a new PCV. I do not think the timing belt have been changed nor the valves been adjusted. I own a 1989 BMW 325ix that needs the valves adjust but it does not sound so loud. I really like the car but I am worried I might have a problem with my rod bearings. Does the rod bearing knock only happen at certain RPMs?

I did an extensive search and read many many posts regarding the engine knock but it seems like everyone had a knock on idle not at certain rpms only.

Your input and help is very much appreciated!

[Riff Raff]

I do not hear a knock on idle but do from 2.5K to 3.5K rpm or so. I also believe the knock gets louder on load (driving it in 1st gear for example).

Since the knock gets louder "under load" (gas pedal input), then I suspect cheap low octane gasoline causing "detonation" (knocking when applying gas pedal input). Run your VX to near bone empty, and then put in a full tank of high octane "Premium" grade gas from a reputable brand (i.e. Chevron, Shell, 76, BP, Texaco). Never, never, use ARCO (their gasoline totally sucks).

[99_VX]

I did fill up from chevron. I was wondering if seafoam treatment made the knock louder. I have used seafoam before and it has always smoked after getting it in the vac line/intake but it did not this time. Anyone had a bad experience with seafoam?

[circmand]

while running it to empty you can add octane boost to help a bit. Or if you have a track or airfield around you might be able to find some 110 octane which will blend and raise the octane level.

[MSHardeman]

Stupid question, maybe, but are you sure it's the engine knocking? I get what sounds like a valve clatter under load also, but aren't our cars supposed to have all kinds of fancy knock sensors and such to prevent knocking? I think my noise might actually be one of the heat sheilds under the VX rattling around when the engine is under load and vibrating a bit. I haven't gone down the road with my head hanging out of the window to try and pinpoint the noise yet, so I could just be talking smack.

[99_VX]

I can hear the knock when parked and revving the engine by hand. My heatshield used to make some noise but I took care of that. I am pretty sure it is coming from the engine. That said the heatshield was making a terrible noise before I secured it. Has anyone done a valve job on the VX? I thought we had hydraulic lifters but read somewhere otherwise.
On a better not I am reupholstering my front seats with european leather .
Did you guys know the back seats are vinyl?

I really appreciate all inputs.

[Gussie2000]

Make sure the belt tensioner is in good conditions,usually causes a knocking noise when it goes bad.

My VX has a knocking,but is valve related and probably rebuild the entire engine next year

[mantis465]

I thought we had hydraulic lifters but read somewhere otherwise.

vx has over head cams. which means no lifters solid or hydraulic, cam is directly over valves so no need for push rods or lifters.

and yes they can be adjusted but you need shims to adjust them

[samneil2000]

Could it be the injection you are hearing? I know they can make a good bit of racket.

[SilverBullet75]

Your symptoms sound just like mine.
http://http://vehicross.info/forums/showthread.php?t=13176&highlight=Belt+tensioner

[Gussie2000]

Your symptoms sound just like mine.
http://http://vehicross.info/forums/showthread.php?t=13176&highlight=Belt+tensioner

I strongly believe this is the same issue my horse is suffering

[99_VX]

I went ahead and chaged my oil to Mobile1 10W40 and put in 91octane and it runs with a barely noticeable knock now. FYI the driver and passenger seats with rails are not interchangeable. The frames are higher on the inside of the seats.

[Dmitrikr]

I strongly believe this is the same issue my horse is suffering

yes, mine was tapping noise at 2000-3000 rpm - loose t belt. tensioner pulley (BUSHINGS) seized up.

[Gussie2000]

99 VX

Seats are exchangeable,( I did it last hear ) but not the rails,the job is a bit tedious.

[MSHardeman]

Ditto what Gussie said. You can switch just the rails from one seat to the other. My driver side seat was starting to get worn so I switched them over with no issues. The only thing is that you will lose the tilt/slide function of the passenger seat as it has a small tab welded to the tilt mechanism that is triggered by a cable mounted on the slide mechanism on the passenger side. The driver's seat does not have the little tab.