Thread: Kerchunk!

I have a '97 GTP I bought new with 220,000 miles. I had it running like brand new and then "kerchunk" and it was as though it suddenly was running on four cylinders. After a few seconds it suddenly cleared up. It's a noise I've never heard from any engine. It's a single "kerchunk" when it goes down and no noise at all when it clears up. It goes through this cycle perhaps every five minutes or so. It seems to be random. I have a guess as to what it is but I'm looking insight from those who know this symptom before I tear into it. Somebody give me good news...

It's been setting for a while, waiting on me to find the time but I don't believe there were any. The wife was driving it when it started happening. I test drove it once after that and immediately parked it.

It's definitely an engine noise, nothing to do with any of the rest of the drive line. There's just one loud "kerchunk" when it comes on and nothing when it smooths out.

If you could get a video, that would help greatly.

This worries me enough that I don't want to start it again until I'm ready to pull it in the garage and tear it down. It almost has to be valve train, perhaps a lifter sticking down. I was hoping someone else would've had the same experience to be able to say what the problem was exactly. When the miss goes away it runs fine. It's that big "kerchunk" noise that worries me.

I didn't notice the transmission shifting related to the noise. I think if the AC clutch were locking up the belt would squeal. I suppose the noise could be the the engine torquing against the mounts, as if the transmission downshifted but the engine definitely is running on less than six cylinders just as the noise occurs.

I had been readying the car for the wife to drive. It had been running with a miss for a long time so I changed plugs and wires. It had a serious valve train tick so I included a quart of Rislone Engine Treatment in an oil change. The tick would subside, come back loud, subside until one day as I was driving down the interstate I decided to clean out the heads and in a moment it smoothed out and ran perfectly. No more tick. So there had definitely been a sticking lifter.

I changed the oil again and included a quart of Restore. It ran great. I finally got everything fixed. The wife started driving it. She was excited that it ran "like new". Then "kerchunk".

Kind of an old thread, but this really does sound like an AC compressor locking up. It's very possible that the belt isn't making any noise; the compressor is probably not locked up entirely but very difficult turn. I've seen lockedup ccompressors prevent an engine from even turning over at work.

Get the belt off and see how well that pulley turns, just about guarantee that's what is going on, as there just isn't anything else that would go "kerchunk" then go away.

That you've seen something close to the kerchunk is interesting. I've been afraid to run it for fear I'm might do irreparable damage but I suppose I'm going to have to roll the dice especially in light of what you say. Thanks for your input.