• Hello Guest, we are proud to now have our Wiki online that is completely compiled and written by our members. Feel free to browse our Jeep-CJ Wiki or click on any orange keyword when looking at posts in the forum.
    To dismiss this notice
    click the top right X.

4.2L acts like it's governed

4.2L acts like it's governed
Touché, my friend, although it is inconceivable, you have bested be in my Monday morning mentally weekend state.
 
Down pipe has no heat riser valve. Engine has ran this way since MC2100 was installed. Got her to 50 MPH, 2100 rpms after replacing the fuel pump. Took her sweet time getting there. Engine sounds terrible with the timing @ 14 dregees, but I can't describe the sound. Couldn't get the tranny into 1 or 2. Came home & checked the shifter out on line. It's a B&M truck mega shifter. I didn't know you had to ratchet it to get into 1 & 2. Will drive again today & get you some rpms.
 
I seperated the exhaust system @ the cat, just ran the open downpipe. Got 2500 rpms in 1st, 3000 rpms in 2nd & 2200 rpms in drive. She just stops accelerating.
 
If you have a rattling or pinging sound you have your timing advanced too far, try it at 12 deg. Sounds like you have 1 or 2 deg of stretch in the timing chain which is normal so you will want adjust it up to compensate for the stretch, the rest will be adjusting to altitude.

From the sound of this it is isolated to the fuel system, what was the reason for the change in carb? Was the carb a rebuild or new? Was it a bolt on or did you need an adaptor? There are a lot of little passages in there that can get blocked. What was the old carb, and what happens if you put it back on?

You may really benefit from taking it to a local performance shop with a dyno and an exhaust sniffer, or if you have dyno emission laws in your area you could take it there, have them run it to the mph you are having the trouble at, and see if you are leaning out.
 
It's a rattleing sound. I took the 2 bbl off the 360 in my J-10. Engine is acting & sounding the same. 55 mph tops. It had a Weber. I changed to the 2100 because the Weber ran very rich & wouldn't pass emissions testing. I couldn't find anone local to help me with it. When the Weber was on, the exhaust looked like I had a diesel. Plugs were coal black. MC2100 was a new rebuild from Church's auto parts & required an adapter. It was rebuilt in 2008. Timing is set @ idle, correct? I don't have the Weber to put back on, but the guy that purchased it said he bolted it on & his AMC 258 i6 / 4.2l runs great.
 
Last edited:
The rattling is because the engine is pinging, you will need to back the timing down a bit. It is set at an idle with the vac advanced un hooked and hose plugged.

That is rather surprising that you could not find a shop to do the weber, they are incredibly easy to build, in fact you feel a little ripped off when you buy the rebuild kit due to lack of parts in the kit. I run only weber carbs, the 2 bbl for the Jeep or if a V8 I run the Edelbrock AFB which is built by weber.

I would make sure your butterflies on the throttle plate is not contacting the adapter, and I would have the carb rebuilt or inspect the internals at least. Or better yet get your hands on a weber.
 
I pulled the plugs to check them. Gap was .040, reset to .035. #5 was wet oil fouled, all others were tan. Champion plugs- RC12PECS. #1 & 6 don't have as strong a spark as the rest. When I held them against the blok to watch the arch, them didn't seem to be firing every time they should have. I watched the timing lite while grounding #1. 1 & 6 have 90 degree ends @ the plugs, the rest are straight. All are 7mm radio supression wires. I had to set the timing 3 times today. Every time i would rev the engine to 4K in park, the timing advanced. Gotta fix the fuel gauge sending unit. Ran out of gas on 1/4 tank. I didn't unhook the vacuum advance as there was no vacuum there @ idle. Vacuum advance hose is hooked to carb on the passenger's side bottom. Timing is 10 degrees, 900 rpm idle.
 
Oil Fouled bout be something to be worried about, I would run a compression test. As the RPM rises and falls when you adjust the timing you could be opening the vacuum port enough to affect the timing, that is why you should always unhook the vac advance, it could also be the reason you are resetting the timing.
 
Does your distributor advance run from the thermostatic switch on the drivers side of the block?? is there a vacuum feeding the switch?:cool:
 
Vacuum advance comes from a port on the passenger's side bottom of the carb. I have a fitting on the intake manifold that has 5 nipples on it. It does have vacuum. That's where one of the hoses from the canister hooks to. In the article, MC2100 on a AMC 258 i6 / 4.2l , it said to get the vac for the dist from the port on the passenger;s side of the carb.

http://street2mud.com/webfiles/MC-2100 set up for a 258.pdf
 
I guess the question should have been, if you are connected to the switch, is it working? but if you are going to the carb I guess it is of no concern.:cool:
 
now I am reaching, but if it isn't the intake and it isn't the exhaust. Havee you checked the coil??
 
Entire ign is new, dist pickup, coil & ign module. Took her to a shop yesterday. Tired of foolin' with her.
 
The shop that has the Jeep says there's a slight noise when the engine is cold, but goes away when the engine reaches normal operating temp. They aren't charging me, so I'm not pushing them. I was talking to a guy yesterday about the "won't go over 55 mph" problem. He said it may be a gearing problem. Is this possible? If it is, could someone explain to me what he's talking about in plain english? Remember, she has 32" tires with an automatic tranny & speed does increase going down hill. I say that because he asked that question before stating it may be a gearing problem. I called the shop & John said he would look into that as it was possible, but he didn't have time to explain.
Thanks
 
Dummy me put my adapter plate on backwards and that was holding up the butterflies. The symptoms were pretty much the same as yours. In the 80s alot of Cjs came with anemic 2.73 gears. Not sure if that carried over to the Yjs though.
 
Petescj said:
Dummy me put my adapter plate on backwards and that was holding up the butterflies. The symptoms were pretty much the same as yours. In the 80s alot of Cjs came with anemic 2.73 gears. Not sure if that carried over to the Yjs though.
Click to expand...
My J-10 has 2.73 axles and it doesn't stop it from running 85 and 90 MPH with no problem at all, I don't buy the gear thing. I don't think a little piston slap is your problem either.:cool:
 
You must log in or register to reply here.

Jeep-CJ Donation Drive

Help support Jeep-CJ.com by making a contribution.

Help support Jeep-CJ.com by making a contribution.
Goal
$200.00
Earned
$40.00
This donation drive ends in
0 hours, 0 minutes, 0 seconds
  20.0%
Contribute
Back
Top Bottom