Can't loose that ping

yeah, I have to get a 4.0L manifold. I have the head and the valve cover. I need the manifold and a kit for the head bolts (7/16 to 1/2 inch).

shouldn't be too much more in parts. mostly labor at this point. something I didn't really want to do but no way around it.

bill

What is your compression?

Is your distributor maybe worn so it advances too far or too easy?

Someone told me that the advance should top out at 2300 rpm. Maybe check that on yours by marking the slot white so you can see it through the fan blades or mark a spot in a measured static advance for reference.

Maybe someone knows for sure what the top end for advance is for sure? If it tops too fast you can get a ping.

Vacuum leak? Maybe try a spray of carb cleaner along the manifold gasket and TB base plate to see if the idle bumps. Same for vacuum lines.

What happens if you pump the brake pedal fast a few times?

Something simple is likely to pop up I am thinking.

Mike

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

William Oliveri wrote:

What programming tool are you speaking about?

Hi Mike,

So if compression was an issue it would be too high? Too low of compression wouldn't make it ping would it?

How do you determine if the distributor is worn? It looked good physically when I put it in.

What does it mean by the term "advance"? What's the opposite of advance?

What is the negative effect of pumping the brake pedel fast? What should be the desired effect when pumping the brake pedel fast?

I'm not clear on this. Is this checked with a timing light?

Thanks,

Bill

Too low compression would make it ping? I thought ping was caused by gas igniting before the spark got to it due to compression. That's why high compression engines use higher octane. Is this right? Why would low compression make it ping?

thanks,

bill

yeah, I looked for those but seem to be difficult to find and somewhat expensive:

I haven't found a single unit yet.

bill

Well, I did have JeepsRUs do this for me when I first had the pinging problem. They (owner, Larie) put it on the DRB II (no charge) and saw no errors at all. Then they retarded the timing by 6 degrees. Still have the ping. This was the owner doing this too who I expect has far more experience with jeeps, mpi and this problem than anyone else in the area.

It was after the DRB II timing adjustment that didn't work that they (Larie) suggested the tornado thingy which also didn't work.

I'm going to call HESCO tomorrow and again Larie this week to see if anything else can be done. Aside from any more voodoo (tornado thingy) or with voodoo I'll welcome a fix. I'd rather not tear the engine apart again but if I gots to do it I gots to do it.

bill

> =2436159222

I'm curious, why would the MPI Kit (the only change from carb) cause an engine to be supsesible to ping? What is it about the fuel injection that causes ping?

Also, I was told that the 4.0L head would clear the ping right up because of the porting on the intake ports. If that's the case, it my problem a cause of poor porting on the 4.2L head?

thanks,

bill

Your suprised the tornado didn't work? Nick

Correct. A 'new' 258 is supposed to have 145 - 150 psi all across. If you are any higher, you have carbon issues and the ATF treatment might be for you, despite the smoke out it will cause.

You will need a timing light to check the advance rate. The springs on the internal timing advance weights can be worn out.

'Advance' means you are advancing the spark to 'before top dead center'. Retarding it is putting it closer to 0 on the gauge or going past to ATDC or after top dead center. Some computer controlled vehicles call for this with a timing light and some advance connections unplugged to test it I think.

'You' want the spark to catch just in time for all the gas/air mix to explode as the piston crests the top of it's travel so you get the maximum downward push.

So for different speeds, you want the advance to be higher or lower so the electricity signal to the ignition module or points and physical moving parts and fuel intake come together at the right spot, the 'sweet spot'.

If the timing is too far advanced, the explosion kicks back on the piston before it crests the top and all the bearings get a physical hit and the piston itself flaps sideways making a 'rattle' or 'ping' or 'knock'.

Low octane gas can start to explode by compression, like diesel does so you have the gas igniting before the spark plug fires off. Octane is added to slow down that burn rate or 'flash point' so the gas waits for the spark plug.

If you have power brakes, they use a big vacuum diaphragm. If it has a leak, the idle will go crazy when you pump the brakes hard and fast. A little rumble and a change in the idle is normal, but a leak won't be that, the idle will go way high and take a while to come back down stable....

Yes, you are looking for worn out springs in the advance mechanism inside the distributor. This means the timing advances before the engine needs it.

If you manually turn the engine so the timing mark lines up and paint the v groove in the flywheel with something like typing white out, then move the flywheel out to the 10 degree mark on the v groove and gauge and paint another spot on the flywheel at the 0 point, them turn that more so it hits 10, then make another mark makes 30, you will still be able to see the marks as they pass the gauge when the timing 'advances'.

The idea is to see at what rpm the advance stops moving, no real matter how 'much' it moves, just what rpm it stops moving.

You do this test with the vacuum advance unplugged and that hose to the carb blocked at the distributor end.

As I said, it still should keep moving until you hit 2300 rpm 'I think that is the right rpm', then stop. Close to that anyway, that is where I get the best torque and gas mileage on the highway too.

I am thinking yours is topping at 1500 or something lower so the advance is too soon for the engine's power band need and it will ping like a bugger for a bit there on acceleration, then mellow out at speed above

2300 rpm where the timing 'should' be topped out.

If that theory is correct, then at 70 mph you shouldn't ping when you pull out to pass or climb a long hill. Try that at 55 mph in top gear with stock tires and it will ping like crazy.

My engine starts a load ping in top gear at around 1700-1800 rpm or in my case 65 mph. I need to run in 4th on the highway at those speeds. That gives me 2300 rpm and 100 miles extra per tank of gas running 91 octane, really good get up and go and no pings ever...

Running right at the 'sweet spot' where the timing comes into sync with the power needed gives me a nice 19 US mpg or 11 L/100 km. In my case with 3.31 gears, that is 65 mph at 2300 rpm in 4th gear turning 33's. My speedometer is GPS calibrated right on too so I know I am getting a real mileage tag.

350 miles plus on a tank of gas ain't too shabby in my book. ;-)

And I still have that Carter BBD in there!

Mike

Huh?????

Mike

"L.W.(ßill) Hughes III" wrote: