Ping revisited

Hrm. When I back it off from 9 deg BTDC, idle falls to crap. Looks like I have some more vac issue hunting. tnx Bill.

I would highly recommend you get an automotive stethoscope and track down the loose part before your engine explodes.

Maybe a bearing cap came loose or one bearing isn't the right size or a lifter is bad...

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

KurtS wrote:

Heh. OK OK. I'll pull out the stethoscope. I don't want to think Mike is right but history has shown again again that he is rarely wrong :-)

Carter's don't have replaceable/upgradable jets? Then you back off the idle mixture.

Just a thought.

--James

So they do (#49 on the exploded view). Find out what jets are in it and get the next size bigger. Then you can adjust the idle mixer with a vacuum gauge until you get max vacuum.

Along the same lines as Mike stated, if you run the engine lean for too long you can damage something.

--James

IF you're setting the timing at idle speed, you're way too advanced.

Set it to 9 degrees with the vac advance hose disconnected and plugged, vacuum switch assy electrical connector unplugged, and engine running at 1600 RPM.

Could also be your knock sensor has gone south.

Sorry for taking so long to get back into the conversation I started. Life is busy right now...

The knock sensor was my next guess. I actually had time to really dig into the thing this weekend and found that the shop had a really screwy idea about proper vac line reconnection, even with the diagram I gave them before the work started. I found the distributor hooked up to ported vacuum and the manifold vac nipple wide open. A couple of others were just hanging loose. Sheesh. Odd that it ran so smoothly for the first 1000 miles.

I did have the timing set 9 deg BTDC @ 1600 so that wasn't it. We'll see how things go from here.

Mike R: I think I was unclear on the ping frequency. It wasn't doing it all the time at cruise - only when I goosed it a *little*. I'd give it more pedal and the knock disappeared. Never pinged on hills or hard acceleration, just most frequent in the pedal range that was *just* past where cruising speed sits.

Someone mentioned jet size as a possible problem. I didn't realize Carter BBDs have optional sizes available. Who sells them? I thought I'd check it out if I end up tearing the carb apart.

You could maybe have had the timing not advancing right from the open port. Have you tried it with the vacuum fixed up?

You are not describing a timing ping though. Pinging or spark knock happens under load, the more load the more knock. It is the gas pre igniting in the cylinders.

Having a 'rattle' or knock when you get lightly on the pedal is a loose part, loose exhaust, loose something. A loose rod bearing cap can act like that.

My stethoscope recommendation still stands....

The carter does have an adjustment inside for the gas metering rods. I find when the are not right, the acceleration doesn't match up with the gas pedal. Open too much and the best acceleration is at say 3/4 of the way down on the pedal. Not enough and you don't get full power at full throttle.

Mike

KurtS wrote:

It's actually much better now the vac lines are correct. I put a stethoscope on it today and didn't hear a thing (in the driveway). I'll have to rig it so i can listen on the highway. The rattle is only noticeable after a gear change or when giving it gas after slowing down on the highway. I CAN feel a slight vibration as the clutch spins down when I push the clutch pedal in. Didn't do that before they changed the clutch. I wonder... Damnit i hate chasing gremlins.

I'll let you know what I find.

I agree, strange vibes ar a major pain!

I chased one for a couple months, changed u-joints, rotated tires, had to stop on the highway once because I thought one or more of my front tires was going to just up and fall off the shake was that bad. It was a bad clutch on the rad fan....

If it is maybe a lean knock, try a spray of carb cleaner or a drizzle of water along the intake manifold gasket. They come loose lots after an engine job.

Did you get the carb mix screws back to their base setting for the stepper motor to work right? Someone here posted how to do it and I saved it if you would like to see.

Basically if you look down the carb, they should be pulsing in the middle of their travel, if they are pinned to either side, you have other issues or the mix screws aren't set right.

Mike

KurtS wrote:

I read that again.

A systematic vibe and a knock, well...

There is a cover plate on the bottom of the flywheel you can remove to see if a bolt is backing out of the pressure plate and ticking something.

Mike

KurtS wrote: