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Engine Pinging Issues

Engine Pinging Issues
T

thundley57

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Location
Bakersfield, CA
Vehicle(s)
1983 CJ7, 258 cu, Howell TBI upgrade
Was wondering if anybody runs their AMC 258 i6 / 4.2l I6 engine with no vacuum advance at all? I can't seem to get an annoying ping to go away which occurs at higher rpm's 2200 - 2400 and when pressing the throttle (loading the engine) while at normal cruise. At normal cruise with maximum vacuum there is no ping but as soon as I step on the gas a bit it starts.

I've read all of the timing articles that I can find on this forum and a few others but the only way I can get it to go away is by removing and plugging the vacuum to the vacuum advance diaphragm. Initial timing is set at 8 degs BTDC.

I've tried running on ported vacuum and manifold vacuum, tried adjusting the diaphragm pre-load from all the way in to all the way out and everything in between. Inspected the centrifugal weights which seem to be in good condition and have tested the advance diaphragm with a vacuum pump which has smooth operations

I would think that with the lower vacuum during engine load would drop the vac advance and prevent the pinging? Do I need to install stiffer springs on the centrifugal weights and or somehow limit their travel? Is there any harm in running with no vac advance or does it only affect fuel economy?
 
I also have had to deal with pinging issues, it now seems pretty manageable. Lowering the initial timing did help, I currently run at 6 degrees. I do mostly street and trail driving which seems to develop hot spots in the combustion chambers which makes it ping. Freeway driving, mashing the pedal, and fuel additives does seem to help with that. Keeping the fuel pressure on the low side seems to work also, like around 10 p.s.i. The distributor vacuum line is hooked up and use 87 octane gas. Howell does recommend a pretty hot spark plug but I still run Autolite 985s.
 
Last edited:
Torxhead said:
I also have had to deal with pinging issues, it now seems pretty manageable. Lowering the initial timing did help, I currently run at 6 degrees. I do mostly street and trail driving which seems to develop hot spots in the combustion chambers which makes it ping. Freeway driving, mashing the pedal, and fuel additives does seem to help with that. Keeping the fuel pressure on the low side seems to work also, like around 10 p.s.i. The distributor vacuum line is hooked up and use 87 octane gas. Howell does recommend a pretty hot spark plug but I still run Autolite 985s.
Click to expand...

Thanks Torxhead. Do you run ported or manifold vacuum to your vacuum advance?
 
Try a tank of premium gas.;)
Also-make sure to put a couple drops of engine oil on the distributor center shaft(under the rotor)to keep everything moving 'rite'.
LG
 
You already have the computer, have you considered computer control timing.
It's the way the system you have should be setup, otherwise your only getting half the benefit of FI

6cyl ported vacuum, V8 manifold vacuum
 
Posi said:
You already have the computer, have you considered computer control timing.
It's the way the system you have should be setup, otherwise your only getting half the benefit of FI

True, but since the existing system is smog legal as it is, It would take a smog referee to approve it. I don't think that would happen anyway. Although, it would take a pretty bright smog checker to catch it if it was done. From what I have read on the forums, guys just back off the initial timing and sometimes use premium gas.
Click to expand...
 
Do they really pull the distributor cap, rotor, distributor plate to check to see if the weights are free? Seems like a lot of work and ridicules if they did, but you would know better living there.
 
These are for PRK use, and to pass SMOG you can't mess with the programing.
That's why I suggested just going to prem fuel. ;)
LG
 
Yeah, they don't want us messing with the air we breathe. Currently, within my view for the past 3 days there is a huge mountain fire going on. I got a recorded phone message stating that people with breathing issues should be on oxygen. Something is always burning anyway here in the birth place of smog restrictions, I have been watching that big DC10 tanker.
 
I already use premium fuel 92 octane and add a dose of StarTron Enzyme Fuel treatment which claims to "cure & prevent ethanol problems". Gasoline here in CA is 10% ethanol most everywhere. I will try the oil to the dist shaft.

Torxhead, it sounds like you have resigned yourself to the fact you're going to have some ping in certain operating conditions, is this true? Mine isn't terribly bad in fact if I'm driving with the windows open I have to lean forward closer to the firewall to actually hear it. Maybe I should quit worrying about it? I know it is probably slowly and steadily causing damage though.

I'm going to try retarding the timing back to 6 deg to see if there is any improvement and maybe try experimenting with different strength centrifugal advance springs. Does anybody know where to buy spring kits for the stock motorcraft dist?
 
I would suggest going to 4 degrees just to make a difference. I assume you have adjusted the vacuum canister to get a minimum ping. If I do a lot of street driving, it will ping up a steep hill, but by the time it gets to the top it is o.k. after it cleans out. I have not been able to find an aftermarket advance spring kit for the AMC 258 i6 / 4.2l .
 
I know you guys are running Howell inj , but mine pinged like crazy with the MPI until I did the 4.0 head swap.
 
I have not done any type of a FI conversion, so let me ask this....
Do you 'loose' the OEM, Knock-Sensor' with this switch to FI? :confused:
LG
 
Lumpy Grits said:
I have not done any type of a FI conversion, so let me ask this....
Do you 'loose' the OEM, Knock-Sensor' with this switch to FI? :confused:
LG
Click to expand...

Yes you do lose the knock sensor with the Howell Howell TBI upgrade. Mine pinged even worse before the upgrade though so maybe it wasn't working. All the wiring looked stock so I don't think the PO did a nutter on it.

Apparently a lot of Jeepers have the same issues after doing the upgrade after reading the lengthy thread Torxhead sent in one of the above posts.

hole said:
I know you guys are running Howell inj , but mine pinged like crazy with the MPI until I did the 4.0 head swap.
Click to expand...

How difficult is this upgrade? I guess you need new intake and exhaust manifolds as well right? I just got through removing the head on mine last year to replace the head gasket which wasn't super diffult.
 
Lumpy, for the Howell conversion the knock sensor is removed. The conversion should run on 87 octane and I would say mine works pretty good with it. In my opinion, the AMC 258 i6 / 4.2l does not run very well with the top end ignition timing above 28 degrees. Per the instructions, a Nutter by-pass is done where the computer does not control the ignition.
 
If you get the 4.0 head with the water jackets already welded up its no different than a head gasket R&R. I used a OEM 4.0 exhaust manifold(header) and just re-installed the 4.0 MPI intake I already had on. You will have to modify you exhaust to mate up with the collector, I opted to run all new 2 1/2" while I was doing my swap. The head swap made a big difference across the board in every aspect. Not sure if/what complications there are putting the Howell setup on a 4.0 head, never seen one personally. I'm sure somebody on this board can enlighten us better ;)
 
hole said:
If you get the 4.0 head with the water jackets already welded up its no different than a head gasket R&R. I used a OEM 4.0 exhaust manifold(header) and just re-installed the 4.0 MPI intake I already had on. You will have to modify you exhaust to mate up with the collector, I opted to run all new 2 1/2" while I was doing my swap. The head swap made a big difference across the board in every aspect. Not sure if/what complications there are putting the Howell setup on a 4.0 head, never seen one personally. I'm sure somebody on this board can enlighten us better ;)
Click to expand...

I would think that the 4.0 head combustion chamber is a lot cleaner than the older AMC 258 i6 / 4.2l and not as susceptible to carbon deposits which of course cause the pinging. When I watch the injector spray as the engine runs, it does seem to have quite a bit of spray coming out. Yet it does perform better with better gas mileage. Just a thought.
 
When one does the FI conversion, and especially with the 4.0 head swap.
Do you run the OEM spec'd AMC/Jeep spark plugs or change to a different heat range? :confused:
LG
 
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