Hey all, this one is a doozy for me that I just can't seem to come up on an answer for here... I'll give some quick background on my car first to set the mood.
Car is an 06' Range Rover L322 with the 4.2l SC jag engine.
Picked her up about 2 months ago with a blown head gasket. I had a hook up on a good donor motor in line that came from a junked car due to electronic failure. I pulled my motor and dropped in the donor motor. During this process found a few other issues that I managed to take care of while I had things accessible easily. Dropped in new Arnott struts and bags for the front suspension. Dropped in a new steering rack and pinion (I accidentally stripped the threads on the high pressure line so, pulled that from the donor car as well).
Once the new engine was dropped in I patched a few vacuum leaks, PCV valve, brake booster line, purge valve. The new engine seems to be running very strong, very nice.
During my vacuum leak testing I found that the idles would start surging. Dropping down to about 500rpm, then compensating back up to 750rpm. No codes were thrown. However I started hearing a rattling sound from the motor. It sounded a lot like the supercharger knock sound from the coupler going out so I decided to service the superchager. I pulled it and cleaned the throttle body really well, cleaned the elbow, everything got a good cleaning. I pulled the snout and found that the coupler was in fact in good condition... So I went ahead and dropped the new one in and did an oil change (much needed) and put the supercharger back on.
The rattle persists!
Well when I got the donor engine it had the SC on it, so I decided to just swap the old SC from the original engine over and just the same, rattle. Upon diving further I found that it seemed like the rattle may be coming from underneath the car.
I've gotten under and can't seem to find any heat shields that are loose or bent or coming into contact with anything. It kind of sounds like the cat has broken down a bit and causing the rattle but putting a dowel on the cat it doesn't sound like it's coming from them.
The rattle will only appear when the engine is warmed up, and upon giving it some gas... Doesn't matter the rpms, if im on the highway and I go to overtake it'll rattle when I accelerate. Just the same as if I'm coming from a stop sign.
Other things I've checked:
I found after a hard drive when I park back at home I can get it to start surging on the rpms a little if I put my old leaking PCV valve back on, with that vacuum leak it'll get the surge going and I can kind of force it to rattle in the driveway.
I've given the thought to timing chains - but since its not a ticking and not consistent I don't think so... Torque convertor same thoughts there, its just not consistent and only on acceleration...
Any thoughts folks?
Car is an 06' Range Rover L322 with the 4.2l SC jag engine.
Picked her up about 2 months ago with a blown head gasket. I had a hook up on a good donor motor in line that came from a junked car due to electronic failure. I pulled my motor and dropped in the donor motor. During this process found a few other issues that I managed to take care of while I had things accessible easily. Dropped in new Arnott struts and bags for the front suspension. Dropped in a new steering rack and pinion (I accidentally stripped the threads on the high pressure line so, pulled that from the donor car as well).
Once the new engine was dropped in I patched a few vacuum leaks, PCV valve, brake booster line, purge valve. The new engine seems to be running very strong, very nice.
During my vacuum leak testing I found that the idles would start surging. Dropping down to about 500rpm, then compensating back up to 750rpm. No codes were thrown. However I started hearing a rattling sound from the motor. It sounded a lot like the supercharger knock sound from the coupler going out so I decided to service the superchager. I pulled it and cleaned the throttle body really well, cleaned the elbow, everything got a good cleaning. I pulled the snout and found that the coupler was in fact in good condition... So I went ahead and dropped the new one in and did an oil change (much needed) and put the supercharger back on.
The rattle persists!
Well when I got the donor engine it had the SC on it, so I decided to just swap the old SC from the original engine over and just the same, rattle. Upon diving further I found that it seemed like the rattle may be coming from underneath the car.
I've gotten under and can't seem to find any heat shields that are loose or bent or coming into contact with anything. It kind of sounds like the cat has broken down a bit and causing the rattle but putting a dowel on the cat it doesn't sound like it's coming from them.
The rattle will only appear when the engine is warmed up, and upon giving it some gas... Doesn't matter the rpms, if im on the highway and I go to overtake it'll rattle when I accelerate. Just the same as if I'm coming from a stop sign.
Other things I've checked:
- Transmission fluid, all good there
- Flex plate bolts, all good and tight there
- Bolts or nuts in the bell housing, seemingly nothing
- Exhaust headers/Y pipe connection, seems nice and tight
I found after a hard drive when I park back at home I can get it to start surging on the rpms a little if I put my old leaking PCV valve back on, with that vacuum leak it'll get the surge going and I can kind of force it to rattle in the driveway.
I've given the thought to timing chains - but since its not a ticking and not consistent I don't think so... Torque convertor same thoughts there, its just not consistent and only on acceleration...
Any thoughts folks?
