hey guys, have got a tn magna that has a 4g54 carby engine, with manual tranny, have been noticing severe flat spots when im accelerating in 2nd, 3rd and 4th gears, its more pronounced in 2nd and 4th, as its all the way thru the rev range, although in 3rd its only between 1200 and 1600.
any ideas what it could be??

Based on similar problems with my Scorpion I would suggest a carby problem and not a gearbox issue.

Not sure if the Magna used the same carby as the Scorpion (Mikuni). I have had quite a few issues with the Mikuni carbs over the years.

There are a few options: You could get the carby rebuilt with a carby kit; You could swap it with one on a wreck and hope that it's better; You can put a Weber on (~$400 on eBay with manifold mounting conversion last time I looked); You can convert to EFI.

The cheapest solution would be to swap with one on a wreck and hope it's better. Maybe they'll let you return it if it's not.

You may also try putting a can of carby cleaner through it, although in my experience this hasn't helped.

Definitely a carb. problem, probably the secondary butterfly not opening, or the choke staying on.

Yep, same Mikuni carb used from the first Galants way back when they still had Chrysler badges on them, just a different model but the same problems - lazy choke staying on, secondary vacuum actuation not working, fuel level inconsistent, crap in the float bowl clogging up jets, etc. lol One from the wreckers would have the same problems. They may still be available new, but they would be very pricey. When I had 4 Sigmas all with carburettors I wished for EFI. No carburettors in the family fleet these days. Oh joy, oh bliss! lol

A fresh Weber sounds a good option.

Thanks guys, didnt even think of looking at the carby, and what do ya know, it is the secondary butterfly thats not opening. any suggestions for a replacement weber or holley carb??

If it is the second throat not opening, you may be able to fix the suction valve thing (I forget what it's called) or a vacuum line but since the second throat is only really used at fully throttle it may not be the main problem. I used to get my carbies from the wreckers for about $80 each, but they aren't guaranteed to be any good. Could be an improvement if you're on a budget.

If the choke is staying on you should notice that it's running rich all the time.

The main body of the carby seems to be plastic (on the Scorpions) and I've always thought this could be the cause of many problems.

I would look at something like this to solve the problem for once and for all: http://cgi.ebay.com.au/MITSUBISHI-SIGMA-SCORPION-GALANT-WEBER-CARBY-CONVERSION-/330545507917?pt=AU_Car_Parts_Accessories&hash=item4cf60c2e4d#ht_594wt_1135

I'm not sure whether or not the linkages will fit on a Magna, but I'm sure something could be worked out there. Also not sure how the Weber would work with airconditioning as the Mikuni carb has a dashpot on the bottom to give it more revs when the A/C is on.

I'm sure the seller would be able to advise.