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Hey yee L-Jet wisemen, my problems with the lurching and all else are being narrowed down to an unhappy (albeit 36k young) motor. It idles with a pronounced miss and burps & coughs & bucks when given the gas, eventually it smoothens out and runs perfectly beautiful afterwards. Done the usual tune up stuff, plugs, points, condenser,......no change. Also upon looking at the old plugs found the left bank rich & black while the right bank grey & lean. Any thoughts please?

Do a compression test first. It sounds like the valves may be not closing all the way...or havinga minor leak that seals up as they rotate...or a head gasket leak tha tseals up when it gets warmer. Next..check the main injection grounds. Next....look for a vauum leak at that side. Check the connector boots for the runners and check the injector seals. Also check the connectors to the injectors themselves on that side. Check injector resistance and part #'s. Ray

hi, ray , do you see the info . for trns,

I had (still have, really) a '94 Voyager that did exactly the same thing. It turned out to be the ignition coil pack crossfiring between two coils. Strange symptoms for a coil, but it turns out the transition from idle (initial throttle tip-in) has the highest voltage requirement for proper plug firing (other than WOT, max output, which is also pretty severe).

Now I know, the T4 doesn't have a coil pack, but it does have ignition wires...if you've got crossfire between two or more wires, you'd get the symptoms you described. You can check them in a darkened engine bay with the engine running, look for blue corona discharge around closely-spaced wires. Be careful of Carbon Monoxide, no closed-up garage while running, though I'd like to meet you and your 412 someday .

Ok guys, will do, thanks for the leads. Truely appreciate it.

umm........just a fleeting afterthought, could a rusty tank or water in it cause the rough idle/running problem. I discovered that the gas return tube from the filler neck to tank is a goner (just replaced it) and that I know leads to water getting in the tank. Any thoughts?

Junk in the tank is always a possibility. A couple other things though. Check the condition and adjustmnt of the TPS. That will not cause an idle problem but can cause misses when taking off the line.
Next...check your timing. Is it erratic at idle? This is common to rust and slop in the advance plates in the dizzy. Check that copper ground braid inside the dizzy to. Also, check to make sure that the advance plates are not binding when you rev it with the timing light on it. Also...have you adjusted the valves? Ray

raygreenwood wrote:Junk in the tank is always a possibility. A couple other things though. Check the condition and adjustmnt of the TPS. That will not cause an idle problem but can cause misses when taking off the line.
Next...check your timing. Is it erratic at idle? This is common to rust and slop in the advance plates in the dizzy. Check that copper ground braid inside the dizzy to. Also, check to make sure that the advance plates are not binding when you rev it with the timing light on it. Also...have you adjusted the valves? Ray

So is Junk in the Tank worse or better than junk in the trunk?

sorry..............

Not at all!...when the car supposedly runs out of gas...you may have time to inspect that "junk in the trunk"... Ray

with junk in the trunk your gas mileage suffers nut not the idle Hey, isbt there supposed to be a drain plug on type 4 tanks? may be I should do a drain job, or is it better to do the old suck on the hose to get the water at the bottom.

Yep, drain plug, 6mm allen.

Hey, I would check that point plate braided wire and throttle position switch!
I think I remember someone opening one and finding a crud pie,lol!
I swear I had this kinda problem too but cant remember if it was the braided wire. Ray, can the hoses on the pvc thing if wrong cause some bucking or charcoal box or is this a ignition type problem? I guess I would pull each of the injector leads to the injectors to see if it was one cylinder or all. Do You have the bottom points in your dist? I didnt think the L-jet had them or MPS? I had big air leaks around the intake tube big rubber hoses. I toke a ink cart. re-filler injector and put alcohol in it and tested all the hoses connects. You could tell instantly there was a vacuum leak by the change! I have some L-jet stuff and misc dist. stuff
I bought a new point plate from street and sand toys when I couldnt get that wire fixed! Its does matter!! Good Luck!!! Bill

Hey vwbill, will add the dizzy check to the rest of the list, although the darn thing looks practically new (36k), but you never know. Do I have a PCV on the L motor? where? I did pull the left side injector plugs and both are ok, the right side is a different story on an L motor, as you must remove the air cleaner box and all that is attached before you can see the injectors on this side . L motors do not utilize trigger contacts for the dizzy, only D motors. Sometimes I wish I had an earlier motor than 74, so I wouldn't be going thru that damn learning curve (my T3 is D-jet and I am familiar with it). I sprayed some WD40 around suspected areas of leak and got no response, maybe it is the wrong hydrocarbon to use, will try carb cleaner next. I have some psare advance plates to use if need be. it will be a couple of days before I can get another stab at it, will let yall know the scoop.

An (unlit!) propane torch always finds the intake leaks for me.

If you decide to open that plug on the bottom of the tank, watch out for the crapstream that's sure to come out...it splashes on the front suspension crossmember unless you figure out a way to deflect it, and makes a mess all over the driveway . I had an oil drain bucket underneath, and it still found ways to splash about and miss the bucket.

Yeah, the PCV valve leaking will cause great trouble on D-Jet engines (so I've read), it's worth a check, even though you've got L-Jet.

Most of the L-jet that was in sedans and wagons had a different type of PCV. It was that mushroom style flap valve assembly with a constant orifice...that is plugged into the grommet in the top of the oiler box. Some very few early L-jets may have still had the PCV valve...and yes...it will cause bucking if the PCV valve is shot. If you have a 12mm hose mounted on a plastic nipple next to the oil funnel on the oil breather...and it goes to the plenum...you have a PCV valve. Do a search on working with a constant orifice. I have written much on the PCV. Ray