Running out of ideas and figured I would ask. 289 in my maverick is idling really really rough. Ive tried several things with no luck..... Adjusted timing all over the place replaced timing chain set ( had slack in it ) Replaced driver side motor mount ( had a crack in it ) Checked for spark ( got shocked all 8 times ) Converted to electronic ign also Checked valve lash ( both running and off ) Adjusted Carb ( slight improvement but not much ) Checked for vac leaks ( found small vac leak around carb and re tightened ) I'm sure ive done more then that but I just can't figure it out. its so rough that it shakes the fenders and the inside of the car. As soon as you give it some gas it smooths right out as if it never had a vibration.......get back down to idle and you'd think it had a 600 lift cam in it. Um..... bout all I can think of right now. Bone stock motor with stock cam. New 4 barrel edelbrock 1406 and performer 289 intake. Fresh motor. Any tips or ideas appreciated
If it's a new cam, pull the valve covers again, then with them off, start and let it idle. Look at all 16 pushrods and verify that all are rotating while the engine is running. If any are not, then you've got cam lobes and lifters wiping out. Otherwise go back over the firing order again and look for more vacuum leaks. Use spray carb cleaner and spray everywhere there could be a leak while it's running, if there is, you'll know when the carb cleaner gets sucked into the leak.
Set idle at 1200 RPM, problem solved... Seriously though, what is the vac at idle??? A collapsed passenger side motor mount that is allowing metal to metal contact would possibly give a similar issue, even trans mount can do same...
yep.. that mentioned above.. and the intake flange/gasket could also be leaking after the swap. In my experience.. edlecrocks are only a step or two above chinese knockoffs sometimes.. with horrible machining and/or casting irregularities in some instances. Engine and head machining during rebuild can sometimes add more variable as well. also.. sometimes it's tough to perceive a lobe that's getting wiped as the engine is running(tough to see a .100 thou difference at full lift unless the lobe base is going too and there is slop(which you'd surely hear). I would also recommend an oil drain(not necessarily to change it) for proper oil inspection to shed light on internal issues. In fact.. I usually start there first to check for metal debri and put my mind at ease for the rest of the troubleshooting process.
Cam is not new. The valve train seems fine and operating as it should. Dont know vac at idle because I don't have a vac guage. Thats on tomorrows agenda. Passenger side motor mount seems normal but who knows. I'm waiting for another motor mount to come in.......parts store only had 1. I sprayed mass air flow sensor cleaner all around and found a vac leak around the carb which I fixed but didn't notice any leaks around the intake or anywhere else. I did a compression check today and all cylinders were 130-150 with no drastic changes between any two cylinders to make it seem like a dead cylinder or a head gasket. 1 think i did notice is that the plugs have a tarnish on them at the base of the plug???? If I clean them and run the car for 10 seconds it comes back. Possibly bad gas left in the tank or oil? Dont get any smoke at start up and no oil smoke to speak of. Worst thing I get is a little black smoke when i floor it...haven't gotten as far as adjusting the carb past idle circuit. Checked torque on head bolts and they are correct................ Thinking could it possibly be the harmonic balancer?? Saw that the rubber isn't in the best shape. thanks for the post guys
Oh and car ran the same with the stock two barrel intake and carb on it so that should help eliminate a carb problem............maybe lol.
being that its a 289 if the heads were never gone thru then it has soft seats and running unleaded gas will kill the seats
Could I do anything to test that? Would that cause the rough idle? Exhaust note does sound a little strange to me. Hard to explain.....almost sounds like a light popping coming through the rest of the exhaust note
how old is the gas in the tank? i had 3 month old gas in my car after doing a project on it and it ran poorly. i put fresh gas in and it was as good as new.
I'm going with bad gas also. I have seen gas go bad pretty quick lately.. They say that different gasses come around with seasonal changes also.
Well I bought the car taken apart with what I though was an empty tank. Could be its loaded with old gas sludge. I've added 8 gallons of 93 but I will get a jug of fresh gas tody and see if I can't rig it to run out of the container. Ifnits bad gas after a few minutes i would guess it would clear up
i have had several brand new edelbrocks have problems right out of the box. ive had a float stuck from its adjustment tab not being set correctly. ive had a bent metering rod in one. ive had a bent secondary lock out rod in one that would not allow the secondarys to open. if the problem is at idle only and you can fix it with the mixture screws i would be talking the carb apart and checking the idle passages for blockage. i have a spare carb around the shop that is know good that i will swap in to see if that fixes problems that are baffling. see if you can borrow a buddies carb that you know runs good and see if that fixes the problem or not.
