I have a 2005 GT, 5-Sp. 55K

When I start it up it sounds awesome. I can rev it up and still sounds great.

When I take it out for a drive there is an extremely loud knocking sound. Once I get rolling and just drive down the road (no load) the sound goes away until I have to accelerate again. I originally thought it was the transmission so I pulled it and had a shop go through it and found everything in perfect condition.

If I decide to just drive it, after about 15 miles it tries to stall out and not start and has major loss of power. If I let it sit for about an hour it will start right up and go about another 15 miles before stalling again (repeating the process).

Any suggestions?

 

are you getting any engine trouble codes? (DTC's)

i would do cylinder compression checks before driving it anymore.

 

No. No codes and I have parked it till I figure this out.

The transmission is still out so I can't do a compression check right now.

 

Check the ECU for DTCs though I suspect you may not get any 'cause the problem sounds mechanical.
Try to localize where the sound is coming from. It seems like it may be coming from the engine so I suggest you don't drive the car at all until you find the cause. Otherwise you risk grenading the engine altogether and that would be a very bad thing.

 

Sounds like an oil pressure problem or bad hydraulic lifter to me. Did you check the engine oil for metal?
Good luck!

 

I did drain the oil and there was not anything out of the ordinary.

Sorry forgot to add this part: I did pull the valve covers and noticed quite a bit of metal flakes on a few of the lifters (4 or 5) so I replaced ALL of them with new. This did not fix my issue however when I removed the caps from the cam shafts I noticed that this is where the metal flake appeared to have come from. Mainly the back two cam supports on each side. The supports and caps showed wear but I didn't really think this was causing my noise. My other concern on this is I don't see any way to repair this other then replacing the heads since there are no true cam bearings.

If there is a little play between the cam and the cam supports, could this cause the knock under load? I'm now thinking yes, but new heads are major cost especially for a guess on the noise.

 

This is never good. I'm not sure from your description just how many this is, any idea where they are coming from? Have you cut open the oil filter to see what is inside?

 

if there is metal debris coming from the camshaft caps, you need an engine, this damage is usually caused by oil pressure loss to the cylinder heads. if you try to slap some heads and cams on it, it will eat itself up again. the "knocking" noise is most likely coming from the hydraulic lash adjusters (you called them lifters), if the oil pressure is low they will collapse and make lots of noise.

 

I would like to know what mods the car has.

What oil is in the car also.

 

I believe it is coming from the last two cam supports on each side.

I have not cut open the filter. I'm guessing I will probably just find more metal flakes which I already know I have.

I would agree that the cause could be from low oil pressure. However I don't see why the entire engine would need to be replaced. New heads and a new oil pump yes. But why the engine block? Why wouldn't a simple overhaul with new heads work?

I don't believe the knocking noise is from the "hydraulic lash adjusters". If they were collapsed or weak wouldn't this noise be there at all times and especially at high RPM's with revving the engine up. The only time there is a knocking noise is when you are accelerating from a stop or down shifting and getting on it. Then it is a SERIOUSLY (LOUD) noise like someone is smacking the firewall with a hammer. Car in neutral and revving/racing the engine it just sounds awesome (No Nasty noises)

Cold Air (If you can call that a Mod)
Mobil 5W30 SYN