I'm having a bit of trouble figuring out what is causing this knock/ping/gurlge under acceleration between 2 and 3k RPM. It is louder when the engine is cold and it's colder outside. It seems to quiet considerably when the engine heats up. Did an oil change and plug change a week ago, and that seems to have made it a bit quieter. I did my best to record the sound..
any ideas?
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6500rpm
Quality Always Shoots Straight
Loose piston skirt to cylinder will cause a cold engine knock that tends to go away when the engine warms up. The old GM 3.1l was notorious for it when the Teflon patch on the thrust side of the pistons wore off. The rpm range doesn't really fit though, usually it's just as pronounced at idle cold engine start up for the first few minutes.
I'm kind of at a loss. If it was a rod knock or position slap I should hear it all the way through the RPM range (with the piston slap going away when warmed up). I hear it between 2k and 3k while accelerating (not causing on the highway), and sometimes I think I can hear it at idle. I really don't know what to make of it. I run 91 octane from BP (the best quality gas I can get around here). I previously had Valvoline full synthetic in it with a motocraft filter (this was done by the transmission place that did my transmission fluid change). Took the car to Tire's Plus and they put in Pennzoil full synthetic with a firestone oil filter and the noise seems to be slightly reduced. I had a friend of the family that used to be a mechanic ride with me in it, and said it might be a wrist pin knock/slap.. but those are extremely rare (or so I've read).
How many miles on your SHO and what year, deja? Could be a timing issue caused by a cam phaser and/or timing chain. Oil is squirted under the pistons to help them keep lubed and cool. You had to have taken the engine cover off to change plugs. Did you notice how the HPFP sounded? Sometimes there is an issue with the fuel line going to the HPFP.
SHOdded, my SHO has 100k miles on it. I had the engine cover off when I changed the plugs, and listened to the engine while the cover was off. I didn't hear anything unusual with the HPFP, but I'm not sure what I should be listening for.
Well, I think I might know what the cause is. A few nights ago, my SHO started misfiring... bad. Grabbing the codes off a code reader pointed to a misfire in cylinder 2. Since I did the plugs a few weeks ago, I was sure it wasn't them. Bought a new OE coil, and swapped out the coil on cylinder 2. (read online 1 - 3 are by the firewall and 4 - 6 are by the radiator). Misfire is still there, and there is an overwhelming smell of fuel when the engine is running.. so I'm leaning towards a bad fuel injector. Tomorrow my SHO will get towed to a dealership, and hopefully all it is is just one bad injector.
Well, everything got done at the shop. The final results are:
Cylinders 1,2 & 3 needed new injectors. The biggest problem was Cylinder 2. The rubber O-ring for that injector was gone, and the plastic O-ring (?) was broken in half with one half missing. The injector ports look to me almost 100% clogged with carbon. 1 & 3, the rubber O-rings were starting to show stress/tears and the plastic o-rings were cracked. When my guy was in there working, he discovered some wires that looked like they might have been chewed on by a mouse, so those got taped up. Outside of the engine, both rear shocks needed to be replaced (100k miles, and I don't think they were replaced before).
I've attached pictures of the fuel injectors for everyone's pleasure. The final bill came out to be $1300 (the stealership wanted $2500 to do 2 injectors and one shock).
Cylinders 1,2 & 3 needed new injectors. The biggest problem was Cylinder 2. The rubber O-ring for that injector was gone, and the plastic O-ring (?) was broken in half with one half missing. The injector ports look to me almost 100% clogged with carbon. 1 & 3, the rubber O-rings were starting to show stress/tears and the plastic o-rings were cracked. When my guy was in there working, he discovered some wires that looked like they might have been chewed on by a mouse, so those got taped up. Outside of the engine, both rear shocks needed to be replaced (100k miles, and I don't think they were replaced before).
I've attached pictures of the fuel injectors for everyone's pleasure. The final bill came out to be $1300 (the stealership wanted $2500 to do 2 injectors and one shock).
Bank 1 gets most of the wear and tear because of the poor ventilation, I think. Never heard of a missing seal on the FI, that's a pretty bad situation! Good luck to ya, hope that's the last of it. Keep us in the loop as to how your SHO is doing 
Well, a few weeks after getting the injectors replaced... the knock/gurgle is still there. More prevalent when it's cold outside and the engine is cold. When it warms up, the noise quites down. Other things I noticed/done.. switched to Pennziol Platinum Full synthetic and switched to Philips 66 unleaded plus (ethanol blended) and it seems to have a noticeable noise reduction. What I still find odd is the noise is only present between ~2k and 3k rpms. Could it be related to the turbo chargers? Don't one of the turbos hit boost at around 2k rpm?
